American electrics
big...@meeow.co.uk
http://electrical-contractor.net/jt/mainrng4.jpg
and this is the install:
This house was built in 1940, and wired with an early form of
Romex...Cloth wrapper, no ground wire. Apart from the water bond, there
is no grounding. All receptacles are two-prong. The only bath recep is
part of the light over the mirror. The main room, with almost fifty
feet of perimeter, has exactly one receptacle. The only kitchen
receptacle shares a single-gang box with a switch for the exhaust fan.
It sure is a different world over there!
The whole thread is here:
http://electrical-contractor.net/ubb/Forum4/HTML/000135.html
NT
Owain
> This is a US CU:
> http://electrical-contractor.net/jt/mainrng4.jpg
> and this is the install:
> This house was built in 1940, and wired with an early form of
> Romex...Cloth wrapper, no ground wire. Apart from the water bond, there
> is no grounding. All receptacles are two-prong. The only bath recep is
> part of the light over the mirror. The main room, with almost fifty
> feet of perimeter, has exactly one receptacle. The only kitchen
> receptacle shares a single-gang box with a switch for the exhaust fan.
Hmmm. I don't think British wiring would have been much better -
especially with it being war-time.
Of course, our wiring has improved considerably since then; we've even
banned wire-nuts. Theirs hasn't, and they haven't.
Owain
Martin Angove
Owain <owain...@stirlingcity.coo.uk> wrote:
The comment I liked was the one which said something along the lines of
"The hospital where I worked had these things, installed in 1933. They
were replaced when the wards were remodelled in 1995".
Those bods don't seem to like their "thermomagnetic breakers". In what
way do their breakers differ from our modern MCBs?
Hwyl!
M.
--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
... Answers on a postcard please to 10 Downing Street, London SW1.
big...@meeow.co.uk
> In message <111755931...@doris.uk.clara.net>,
> Owain <owain...@stirlingcity.coo.uk> wrote:
> > Hmmm. I don't think British wiring would have been much better -
> > especially with it being war-time.
> >
> > Of course, our wiring has improved considerably since then; we've even
> > banned wire-nuts. Theirs hasn't, and they haven't.
> The comment I liked was the one which said something along the lines of
> "The hospital where I worked had these things, installed in 1933. They
> were replaced when the wards were remodelled in 1995".
Exactly, nail on head. 1930s wiring is common place over there _today_
in 2005. Having no earth anywhere on your presmises is considered
normal, numerous old installs are like that. I've only once ever seen
anything that ancient over here.
> Those bods don't seem to like their "thermomagnetic breakers". In what
> way do their breakers differ from our modern MCBs?
I dont know, but I know enough about merican lectrics to know their kit
is generally of way lower quality than here. For example the standard
insulator on bulb holders is a piece of card, and the standard socket
cable connector is a flat spring, not a screw connection. So I wouldnt
be surprised if their mcbs were slow, unreliable, or overheated.
NT
Andrew Gabriel
Martin Angove <MJAn...@tridwr.demon.co.uk> writes:
>
>The comment I liked was the one which said something along the lines of
>"The hospital where I worked had these things, installed in 1933. They
>were replaced when the wards were remodelled in 1995".
>
>Those bods don't seem to like their "thermomagnetic breakers". In what
>way do their breakers differ from our modern MCBs?
My impression from reading US NG's is that their breakers are
not unknown for burning out, falling to bits, drifting trip
values, etc. which I've never come across with ours. If you
pick the things up in Home Depot and look at them, they just
don't feel anything like the same quality as ours either. The
funny thing is some of them are same manufacturers as the EU
ones, but obviously built to different standards (and possibly
price -- I don't recall how that compared with ours).
Many of their older breakers are thermal only, and don't have
the fast fault current response ours do. I don't know if all
their current breakers have the magnetic trip component.
If you get to go to the US, a stroll through the electrical
section of Home Depot is really quite frightening. However,
you'll find many more things stocked which you won't find
stocked in B&Q and would be special order only from even a
UK electrical wholesaler.
--
Andrew Gabriel
Christian McArdle
> way do their breakers differ from our modern MCBs?
They have thermal trip only. They cost about 1.3p to make in some sweatshop
and are as reliable as a clingfilm condom.
The US electrical system is simply unsafe compared to the rest of the world.
It largely comes down to:
Lower voltage. 110V is much more dangerous than 230V. This isn't obvious to
the non-technical, but the US went with "common sense" (aka thick people's
prejudices) rather than sound scientific analysis. The basic issue is that
very few people die of electrocution, whilst loads of people die from
electrical fires. The electrical fires largely stem from high currents. If
you halve the voltage, you double the current.
The high voltage has other safety benefits, too. For example, during an
earth fault, the higher voltage leads to much higher current flow. An
overcurrent safety device is, thus, much more effective, leading to much
more rapid disconnect of the circuit.
Some numbers. Take a hypothetical circuit rated for a bit over 3kW. In the
US, this would be 110V, 30A. If the breaker requires 5x current to trip
immediately, this requires an earth impedence of 0.73 ohm right back to the
substation. Of course, most US circuit breakers are thermal anyway, so trip
is never immediate. With less than about 0.73 ohm, it will take much longer
to trip (or perhaps it never trips, if the earth loop impedence is too
high). A slightly higher energy circuit in the UK would be 230V, 15A. The
required earth impedence is now 3.8 ohms. This is extremely easy to achieve,
unlike the 0.73 ohm, which might even be impossible.
Another effect of the low voltage is that "respect" for electricity is
lower. The lower voltage leads to lower quality insulation on fittings,
cheaper parts and a blase attitude of users to electrocution. The result of
this is that the US actually has a higher electrocution death rate per
capita than the UK, despite the lower voltage! When you compare the
incidence of electrical fires, the differences become much more scary.
Other differences in the US:
1. Low quality cables that have arcing failure modes, leading to fires.
2. Use of wirenuts.
3. Combination of neutral to earth (i.e. effectively TN-C earthing) leading
to electrocution in the event of polarisation swap, or some open circuit
conditions. TN-C earthing in banned in Europe, except in special
(non-domestic) cases.
4. Provision of socket outlets in bathrooms, so users dry their hair in the
bath.
Christian.
Andrew Gabriel
"Christian McArdle" <cmcar...@nospam.yahooxxxx.co.uk> writes:
>Lower voltage. 110V is much more dangerous than 230V. This isn't obvious to
>the non-technical, but the US went with "common sense" (aka thick people's
>prejudices) rather than sound scientific analysis. The basic issue is that
Actually, the choice of mains voltage on either side of the pond
was not decided on safety grounds. The safety issues were largely
unknown at the time.
>very few people die of electrocution, whilst loads of people die from
>electrical fires. The electrical fires largely stem from high currents. If
>you halve the voltage, you double the current.
and quadruple the overheating effect.
>Other differences in the US:
>
>1. Low quality cables that have arcing failure modes, leading to fires.
>2. Use of wirenuts.
>3. Combination of neutral to earth (i.e. effectively TN-C earthing) leading
>to electrocution in the event of polarisation swap, or some open circuit
>conditions. TN-C earthing in banned in Europe, except in special
>(non-domestic) cases.
>4. Provision of socket outlets in bathrooms, so users dry their hair in the
>bath.
You missed:
5. the crap quality of their socket outlets, responsible for many fires.
6. building regulations which hinder people modernising their wiring,
so extremely old wiring still in use is very much more common.
Oh hang on, scratch that one, we just introduced the same regulations
here.
--
Andrew Gabriel
Christian McArdle
> 5. the crap quality of their socket outlets, responsible for many fires.
Actually I included that under the low voltage section, as it is the low
voltage that makes them think they can get away with it, although I suspect
it is just a cheap as possible, don't care attitude, really.
Christian.
Andy Dingley
>It sure is a different world over there!
There's a "workshop wiring" FAQ somewhere in rec.woodworking. It
terrifies me!
Frank Erskine
<cmcar...@nospam.yahooxxxx.co.uk> wrote:
The electrical fires largely stem from high currents. If
>you halve the voltage, you double the current.
...For a given power rating... :-)
(Just to avoid confusing beginners!)
--
Frank Erskine
big...@meeow.co.uk
> 6. building regulations which hinder people modernising their wiring,
> so extremely old wiring still in use is very much more common.
> Oh hang on, scratch that one, we just introduced the same regulations
> here.
Even with Prat P we dont rent out apartments and blocks all wired a la
1930s in 2005... its either legal over there or not enforced. I suspect
legal, given the litigius society and wide spread of 30s electrics,
waaaaaaaay past their scrap by date. What people often dont stop to
think is that a typical 1930s install today would even fail a /1930s/
safety inspection, due to deterioration and additions leading to
overloading.
NT
Doctor Evil
<big...@meeow.co.uk> wrote in message
news:1117641835.2...@g43g2000cwa.googlegroups.com...
> Andrew Gabriel wrote:
>
> > 6. building regulations which hinder people modernising their wiring,
> > so extremely old wiring still in use is very much more common.
> > Oh hang on, scratch that one, we just introduced the same regulations
> > here.
>
> Even with Prat P we dont rent out apartments and blocks all wired a la
> 1930s in 2005... its either legal over there or not enforced. I suspect
> legal,
No it is not legal. On a large Middle East US site I was at, it was all
conduit and 1930s electrics. In plants rooms not a bit of mineral insulated
cable to be seen (the norm in Europe). I asked why mineral insulated cable
had not been used, and none of them had heard of it. One knowledgeable man
said mineral insulated is used in the US, but infrequently because of cost.
This I found strange as installing metal conduit is not cheap. The merits
of conduit were given to me and how cheap is just to pull though extra wires
or to replace. I asked them how often do you replace wires? Slapping pyro
around the walls is not that expensive in comparison. The US appears
habitual in many aspects, although they did abandon fuses to a large extent.
> given the litigius society and wide spread of 30s electrics,
> waaaaaaaay past their scrap by date. What people often dont stop to
> think is that a typical 1930s install today would even fail a /1930s/
> safety inspection, due to deterioration and additions leading to
> overloading.
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Jim Hatfield
Gabriel) wrote:
>If you get to go to the US, a stroll through the electrical
>section of Home Depot is really quite frightening. However,
>you'll find many more things stocked which you won't find
>stocked in B&Q and would be special order only from even a
>UK electrical wholesaler.
I visit Lowes and WalMart on most trips, and on the last trip
came across shelves and shelves of shotgun cartridges at WalMart,
which was a bit startling.
I have an American "domestic electrical diy handbook" and it's
fascinating. I'd never seen a wirenut before I read that.
Dave Plowman (News)
Jim Hatfield <lo...@localhost.com> wrote:
> I have an American "domestic electrical diy handbook" and it's
> fascinating. I'd never seen a wirenut before I read that.
They were fairly common in the UK many years ago. I found some in my house
used with lead cable. So I'd guess pre WW2.
--
*He who laughs last, thinks slowest.
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
big...@meeow.co.uk
> 4. Provision of socket outlets in bathrooms, so users dry their hair in the
> bath.
Theres a famous picture of an American extension lead made by someone
who remarkably survived. He put 2 sockets into a cut open shampoo
bottle and taped it all up. The idea was it would float. Yep, float, in
his pool. Appaerntly it was so he could watch tv while in the pool.
NT
Dave Plowman (News)
Huge <hu...@ukmisc.org.uk> wrote:
> I replaced the garbage disposal in my mother's house (in Pennsylvania) a
> few months ago.
> Good things; Huge individual circuit breaker panel easily available in
> the kitchen, so no grovelling under the stairs and having to switch off
> an entire ring to isolate the garbage disposal.
You wouldn't in the UK either. It would have been either plugged into the
ring, or isolated by a double pole FCU, etc.
--
*A 'jiffy' is an actual unit of time for 1/100th of a second.
Terry
Useless devices IMHO; today we too compost. Although the heap sometimes
freezes during the winter. Heap also produces worms for trout fishing. Worms
flourish on discarded banana skins, potato peelings, other kitchen discards
of the non-meat variety along with last year's raked leaves.
Recall semi amusing event:
About 48 years ago someone gave us a brand new under sink mounting 'Garbage
Disposal' unit. It had about a third HP 115 volt 60 Hertz motor!
Installed it in the 35 by 8 foot house trailer we then lived in. Worked fine
until the sewer line blocked.
Not knowing line was blocked, or perhaps in an attempt to blow the
obstruction down the pipe towards the septic tank, I forget which, I
switched it on, fully loaded with water and with the tap running!
Result was a jet of water and other 'unmentionable stuff' straight up out of
the vent pipe in roof of the trailer.
A neighbour said "It WAS quite sight".
So was the clean up! Ever try cleaning sprayed 'cr*p' off the aluminium
siding, roof and windows of a trailer (caravan)?
.................................................. snipped
...................................
>> I replaced the garbage disposal in my mother's house (in Pennsylvania) a
>>> few months ago.
>>
>>> Good things; Huge individual circuit breaker panel easily available in
>>> the kitchen, so no grovelling under the stairs and having to switch off
>>> an entire ring to isolate the garbage disposal.
>>
>>You wouldn't in the UK either. It would have been either plugged into the
>>ring, or isolated by a double pole FCU, etc.
>
> Good point. We've never had one, on account of having a compost heap.
>
> --
> "The road to Paradise is through Intercourse."
> [email me at huge [at] huge [dot] org [dot] uk]
>
>
Andrew Gabriel
Derek * <use...@miniac.demon.co.uk> writes:
>
> On Fri, 03 Jun 2005 20:19:20 +0100, "Dave Plowman (News)"
> <da...@davenoise.co.uk> wrote:
>
>>In article <sfou9157r75ak9dic...@4ax.com>,
>> Jim Hatfield <lo...@localhost.com> wrote:
>>> I have an American "domestic electrical diy handbook" and it's
>>> fascinating. I'd never seen a wirenut before I read that.
>>
>>They were fairly common in the UK many years ago. I found some in my house
>>used with lead cable. So I'd guess pre WW2.
>
>
> electrician when I was in the 6th form, that would place it in
> 1963.
>
> They were called "Scruits" (TM)
Yes, that's a tradename. "Dogs Bollocks" was a nickname, which
came about due to the way a pair of them would dangle below a
cable knot.
I have a number of old books on wiring (stangely, I find the
history of it interesting). The most recent one with any reference
to this type of connector is about 1935, and that's only in a
picture -- I suspect thet were probably rather obsolete even by
then. Ceramic chocolate block connectors were well established
by then, together with a one terminal single ended chocolate
block connector which looks like a screwit but cylindrical
rather than tapered. Oh, and today's circular junction boxes
with the slotted terminals just start appearing (with screwed
lids at that time).
> I'm fairly sure I've recently seen them inside multiple ceiling
> light fittings (3-lights etc) and ceiling fans.
Those are single-ended insulated crimps, which look similar but
are _far_ more reliable...
--
Andrew Gabriel
Owain
>>They were called "Scruits" (TM) ...
> I have a number of old books on wiring (stangely, I find the
> history of it interesting). The most recent one with any reference
> to this type of connector is about 1935, and that's only in a
> picture -- I suspect thet were probably rather obsolete even by
> then.
I had an electrical wiring book in the mid 1980s which recommended them.
Can't remember which one though.
Owain
Dave Plowman (News)
Huge <hu...@ukmisc.org.uk> wrote:
> >You wouldn't in the UK either. It would have been either plugged into
> >the ring, or isolated by a double pole FCU, etc.
> Good point. We've never had one, on account of having a compost heap.
I've never seen the point either. Unless in a 45th floor apartment with no
rubbish disposal facilities.
--
*If only you'd use your powers for good instead of evil.
Owain
> I've never seen the point either. Unless in a 45th floor apartment with no
> rubbish disposal facilities.
The Saniflo is not the only waste disposal device invented by a
Frenchman. google Garchey - I think the first site is the Barbican
Estate Underground page, will tell you all you didn't want to know.
Owain
Andrew Gabriel
Well, there are loads of books which recommend them in 2005 too,
to Americans...
--
Andrew Gabriel
Owain
>>>>They were called "Scruits" (TM) ...
>>>I have a number of old books on wiring (stangely, I find the
>>>history of it interesting). The most recent one with any reference
>>>to this type of connector is about 1935, and that's only in a
>>>picture -- I suspect thet were probably rather obsolete even by
>>>then.
>>I had an electrical wiring book in the mid 1980s which recommended them.
>>Can't remember which one though.
> Well, there are loads of books which recommend them in 2005 too,
> to Americans...
Yebbut this was a British book, and referred specifically to Scruits for
doing loop ins in lighting circuits.
I have some genuine glazed porcelain scruits and find them preferable to
any plastic imitators.
Owain
Dave Plowman (News)
Huge <hu...@ukmisc.org.uk> wrote:
> >I've never seen the point either. Unless in a 45th floor apartment with
> >no rubbish disposal facilities.
> My Mum lives in a tiny town house with no (private) garden. In the
> summer, the temperatures stay > 30 deg C for days on end. A garbage
> disposal is essential.
You're cruel to your mum. I hope she cuts you off without a penny. With
your vast house you must have room for a granny flat. ;-)
--
*I don't have a solution, but I admire your problem. *
big...@meeow.co.uk
> Hi,
>
> I will assume that your post is not bait and is serious
You make some good points, but there are a few I'll pick up on:
> On Wed, 1 Jun 2005 10:31:18 +0100, "Christian McArdle"
> <cmcar...@nospam.yahooxxxx.co.uk> wrote:
> >The US electrical system is simply unsafe compared to the rest of the world.
true, at least compared to UK. Maybe not the world, US seems the model
of good practice compared to African practices, and that of many other
countries.
> Current, of course). Edison's first great central station, supplying
> power for three thousand lamps, was erected at Holborn Viaduct,
> London, in 1882. Does anyone know the voltage that was used? In any
> case the U.S. Voltage is due to historical factors. I am sure the
> British voltage was not selected much more recently.
but this doesnt change the fact that 110 is inherently more dangerous
than 240. With 240v we treat it with respect, with 110v people relax
since it wont electrocute them, and hurts waaay less if they get bit.
They worry less about cord grips etc. The result is fires, which are
the prime killer, not electrocution.
> >The basic issue is that
> >very few people die of electrocution, whilst loads of people die from
> >electrical fires. The electrical fires largely stem from high currents. If
> >you halve the voltage, you double the current.
> NOT TRUE.
> You are making multiple invalid assumptions.
> 1. That U.S. wiring has the same number of circuits for the same load.
still cant figure out what you mean there. For a given load you do have
higher i with lower v, and each load is on 1 circuit as far as i can
see.
> 2. That U.S. circuits are not designed for their load.
I dont think that was the assumption: the problem is simply theyre
designed to have a higher incidence of faults. The practice of push-in
connection on mains sockets is something considered unthinkable here,
for good reason. Use of single insulated mains flex has been illegal
for decades, etc etc.
> 3. That electrical fires occur in properly designed circuits simply
> due to higher currents.
we know its due to many factors.
> 4. You claim lower voltage equals higher current, then you say...
> >The high voltage has other safety benefits, too. For example, during an
> >earth fault, the higher voltage leads to much higher current flow. An
> >overcurrent safety device is, thus, much more effective, leading to much
> >more rapid disconnect of the circuit.
> It seems you contradict yourself.
no contradiction there that i see, just an example of how higher v
gives a safety benefit.
> >If the breaker requires 5x current to trip
> >immediately, this requires an earth impedence of 0.73 ohm right back to the
> >substation.
> Note: Our circuit breakers magnetic trip are similar to your type D
should give less nuisance trips, ours sometimes trip on bulb failures.
> >The
> >required earth impedence is now 3.8 ohms. This is extremely easy to achieve,
> >unlike the 0.73 ohm, which might even be impossible.
>
> Again, in the U.S. a 3kW circuit would be 240V 15amp and the same
> benefits would apply.
In US IIUC it would be called 240v, but in fact be 120-0-120, so the
voltage from earth is 120 ac, not 240. In which case the fault
clearance benefit of genuinely 240v would sometimes apply and sometimes
not. Some faults that smoulder at 120 can arc over and trip at 240.
> >Another effect of the low voltage is that "respect" for electricity is
> >lower. The lower voltage leads to lower quality insulation on fittings,
> >cheaper parts and a blase attitude of users to electrocution. The result of
> >this is that the US actually has a higher electrocution death rate per
> >capita than the UK, despite the lower voltage! When you compare the
> >incidence of electrical fires, the differences become much more scary.
> Please quote sources for statistics.
> >2. Use of wirenuts.
> Why Not?
they were banned here long ago because they cause connection failures
and fires. They dont provide anywhere near the clamping pressures of
our screw connections.
> >3. Combination of neutral to earth (i.e. effectively TN-C earthing) leading
> >to electrocution in the event of polarisation swap, or some open circuit
> >conditions.
snip
> In the past it was permitted for the neutral to be used to ground the
> frames of ranges and dryers.
> This came about as Interim Amendment No. 53 put into effect on July
> 10, 1942. This was to allow the neutral to ground the frames by means
> of a bonding jumper from the frame to the neutral. The reason for the
> amendment was to save raw materials like rubber and copper for the
> effort of WWII.
that much is fair enough, but...
> This special amendment however was not removed from the NEC until the
> 1996 code cycle.
remarkable. At least not something normally permitted here. But we do
have a permited 2 conductor wiring system, I forget the details, ISTR
maybe it uses MICC? I'm not sure, but I'm pretty positive there still
is one here, but it is not AFAIK permitted in domestic premises.
> Don't ever accuse us of not making sacrifices ;<)
I think the general complaint was that America makes more sacrifices,
unnecessary human ones unfortunately.
FWIW we had 110 dc here as well in the 50s, but this has universally
disappeared now.
NT
Owain
> remarkable. At least not something normally permitted here. But we do
> have a permited 2 conductor wiring system, I forget the details, ISTR
> maybe it uses MICC? I'm not sure, but I'm pretty positive there still
> is one here, but it is not AFAIK permitted in domestic premises.
TN-C. Earthed concentric wiring (MICC). Very limited applications,
usually restricted to private generating plant or private transformer
supply. Not necessarily banned in domestic premises though, AFAIK.
Owain
Capitol
Jim Michaels wrote:
In any
> case the U.S. Voltage is due to historical factors. I am sure the
> British voltage was not selected much more recently.
Both the US and British voltages are a result of history. The British
started with 100V IIRC, (100V was picked (by Edison)as it is a nice
round number!) then moved up to 220V DC as it was cheaper to distribute
power at the higher voltage. Parts of Camden Town in London were only
converted from this in 1958. When the power supply world moved on, in
the UK, AC was introduced and AIUI the available transformer stampings
were optimal at 50Hz. The US came in with AC a bit later IIRC, and by
then the laminations would sustain 60Hz, reducing the transformer size(
& cost) and centre tapping the 230V allowed the use of the old
distribution circuits and products without upgrading. If we were
starting again today the world would probably settle for 230V @ 400 Hz,
giving smaller ( &cheap) transformers without significantly increased
losses.
The US consumer has a product penalty as a result of using 230V, in
that 2KW per 120V appliance is probably a realistic limit for the house
wiring used, hence electric toasters and kettles are a pale shadow of
the European ones. Also DIY tools, just do not have the "grunt" achieved
by 230V. Dishwashers also are frequently hot fill. However 240V centre
tapped is a lot safer than 0 - 240V IMO. US wiring is, I believe,
produced to a higher temperature performance specification than Europe.
Certainly this is true for internal wiring in consumer products. Having
experienced US wirenuts, I can confirm that they are a fire on the way
to a happening with solid cables and would never be accepted in the UK.
US wiring in conduit is much safer from an accidental shorting viewpoint
than UK wiring just buried in walls and if conduit wires are used, is
much easier to modify.
I believe the UK has very acceptable standards for wiring, but would
probably benefit from using a 120-0-120V system on the grounds of safety
and has gone over the top on equipotential bonding. On a basic level,
who cares if the fault current is not sky high as long as the trip works!
Just a few comments
Regards
Capitol
>
Mike
"Capitol" <cap...@spamfree.freeserve.co.uk> wrote in message
news:d92307$t3c$1...@news8.svr.pol.co.uk...
>
> In any
> > case the U.S. Voltage is due to historical factors. I am sure the
> > British voltage was not selected much more recently.
>
> Both the US and British voltages are a result of history. The British
> started with 100V IIRC, (100V was picked (by Edison)as it is a nice
> round number!) then moved up to 220V DC as it was cheaper to distribute
> power at the higher voltage. Parts of Camden Town in London were only
> converted from this in 1958. When the power supply world moved on, in
> the UK, AC was introduced and AIUI the available transformer stampings
> were optimal at 50Hz.
> The US came in with AC a bit later IIRC,
I don't know what frequency (or voltage) he used but Tesla's company
distributed AC mains in the US before it reached Europe.
big...@meeow.co.uk
> "Capitol" <cap...@spamfree.freeserve.co.uk> wrote in
> > The US came in with AC a bit later IIRC,
> I don't know what frequency (or voltage) he used but Tesla's company
> distributed AC mains in the US before it reached Europe.
Edison decided dc was superior, and many a battle was fought over ac vs
dc. It didnt take long to realise Edison had not made a good judgement
on this point, but he continued his marketing battle by publically
electrocuting animals on ac current for entertainment.
NT
Andrew Gabriel
Capitol <cap...@spamfree.freeserve.co.uk> writes:
> Both the US and British voltages are a result of history. The British
> started with 100V IIRC, (100V was picked (by Edison)as it is a nice
> round number!) then moved up to 220V DC as it was cheaper to distribute
> power at the higher voltage. Parts of Camden Town in London were only
Most of the early generation was at 100V. It suited arc lamps
and the filament lamps of the time. Trouble was it wouldn't
reach further than a few city blocks. I don't think there's
any real concensus why many of the UK power stations switched
to 200V and the US didn't, but one reason which does seem to
have more credibility than others is as follows. Very early
on, many London boroughs banned overhead cables (and those
bans are still in effect today). This forced the cabling to be
underground in much of London, but it was mostly on poles in
the US at the time. Now what do you do when you have a local
supply infrastructure that no longer meets the local demand?
In the US, it was easy, you just string thicker cables on the
poles. In London, with the cables all being underground, this
wasn't possible without doing a complete new installation.
So the way round the problem was to double the voltage, and
we got lots of 200V supplies. Over the years, the voltage has
continued to creep up in small increments. By the late 1950's,
most of the UK mains final supply voltage was in the 200-250VAC
range depending what town you lived in, and it was all changed
to 240VAC in the early 1960's. Some areas with lots of cinemas
also retained DC supplies for some commercial customers -- much
of central London had a 220VDC supply until the late 1970's.
> converted from this in 1958. When the power supply world moved on, in
> the UK, AC was introduced and AIUI the available transformer stampings
> were optimal at 50Hz. The US came in with AC a bit later IIRC, and by
> then the laminations would sustain 60Hz, reducing the transformer size(
> & cost) and centre tapping the 230V allowed the use of the old
> distribution circuits and products without upgrading. If we were
> starting again today the world would probably settle for 230V @ 400 Hz,
> giving smaller ( &cheap) transformers without significantly increased
> losses.
400Hz severely reduces the maximum area of a synchronisation zone,
which makes carrying power any distance very much more expensive.
Many of the 50Hz zones are close to their size limit now, so I
don't think anyone would think of distributing at any higher
frequency in Europe. It would be OK on a small isolated island.
400Hz isn't suitable for industrial motors either. Actually, supplies
to large commercial customers at 16 2/3rds Hz and 25Hz used to be
quite common as they much prefer a lower frequency for large motors.
Transformer size is really only an issue on planes and boats, which
often do use 400Hz.
--
Andrew Gabriel
Chip
<mi...@nospam.com> spake thusly in uk.d-i-y:
[snip]
>I don't know what frequency (or voltage) he used but Tesla's company
>distributed AC mains in the US before it reached Europe.
From http://en.wikipedia.org/wiki/Alternating_current , so it may be
inaccurate but sounds reasonable:
"It is generally accepted that Nikola Tesla chose 60 hertz as the
lowest frequency that would not cause street lighting to flicker
visibly. The origin of the 50 hertz frequency used in other parts of
the world is open to debate but seems likely to be a rounding off of
60hz to the 1 2 5 10 structure popular with metric standards."
From my own knowledge I am fairly certain that a German company was
responsible for the usage of 50 Hz in Europe, it may have been
Siemens, but my memory is fallible :-)
In any case, in a region like Europe, having a well established AC
system of one frequency in the area would tend to encourage the usage
of that frequency elsewhere to facilitate crossover of equipment and
appliances, thus leading to savings in various things I slept through
in economics class;-)
--
The government's view of the economy could be summed up in a few short
phrases: If it moves, tax it. If it keeps moving, regulate it. And if
it stops moving, subsidize it.
- Ronald Reagan
Christian McArdle
> long as the trip works!
Well, because it clears the fault more reliably and leads to fewer fires and
deaths?
Christian.
Capitol
Christian McArdle wrote:
> Well, because it clears the fault more reliably and leads to fewer fires and
> deaths?
>
Where is the evidence for this? Most fires are due to poor connections,
they won't necessarily trip the breaker until much too late!
I noticed some comments earlier in the thread on the phasing problems
of 400Hz. There are no problems if the main distribution system is HVDC.
This is why major power links have been HVDC for many years AIUI. The
50Hz local distribution system is purely historic and well entrenched
but the transformer sizes could be substantially reduced with 400HZ. In
the US, local transformers on a pole appear to be the norm in a lot of
areas. These would certainly be lighter at 400Hz. The 400 Hz suggestion
comes from discussions with US engineers many years ago on which way
would you go today if you could start again. I certainly like it. I
haven't kept up to date with the power side of electrical distribution
for a few decades, but sub 50Hz supplies were normally achieved locally
by six and twelve phase transformers with interphase reactors, and not
generator sourced. Sub 50Hz harmonics can be a major headache for
distribution transformers AIUI so local generation seems essential.
Regards
Capitol
Dave Plowman (News)
Capitol <cap...@spamfree.freeserve.co.uk> wrote:
> I noticed some comments earlier in the thread on the phasing problems
> of 400Hz. There are no problems if the main distribution system is HVDC.
> This is why major power links have been HVDC for many years AIUI. The
> 50Hz local distribution system is purely historic and well entrenched
> but the transformer sizes could be substantially reduced with 400HZ.
One problem is it's slap in the middle of the most sensitive part of the
human audio band. Expect the average transformer to make the most annoying
noise.
--
*Work like you don't need the money. Love like you've never been hurt.
Chip
(News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
>In article <d97hrt$bsr$1...@newsg4.svr.pol.co.uk>,
> Capitol <cap...@spamfree.freeserve.co.uk> wrote:
>> I noticed some comments earlier in the thread on the phasing problems
>> of 400Hz. There are no problems if the main distribution system is HVDC.
>> This is why major power links have been HVDC for many years AIUI. The
>> 50Hz local distribution system is purely historic and well entrenched
>> but the transformer sizes could be substantially reduced with 400HZ.
>
>One problem is it's slap in the middle of the most sensitive part of the
>human audio band. Expect the average transformer to make the most annoying
>noise.
Good thought, ouch. 400 Hz is the NU tone frequency before BT started
using silly announcements, I would _not_ want that in the substation
next door.
--
"The perfect computer has been developed. You just feed in your problems
and they never come out again."
- Al Goodman.
Andrew Gabriel
Capitol <cap...@spamfree.freeserve.co.uk> writes:
>
> I noticed some comments earlier in the thread on the phasing problems
> of 400Hz. There are no problems if the main distribution system is HVDC.
Except for the cost of the converters at each end of the line,
which is astronomic compared with cost of transformers.
> This is why major power links have been HVDC for many years AIUI. The
HVDC is used to cross synchronisation areas. It is also advantageous
in cables where the DC stresses the insulation less than AC. But the
cost of the end station plant and any line switches means it's used
only when absolutely essential. Generally it's much cheaper to make
sychronisation zones as big as possible. Great Britain is all one zone.
I haven't seen a recent map of Europe, but prior to the fall of the
Berlin wall, continental Europe was 2 zones, the West controlled by
Switzerland, and the Eastern European countries controlled from Moscow
(although the USSR itself was multiple zones -- too big for one zone).
The East and West zones weren't linked -- cost of the converters made
it non-viable. GB and the West were/are linked across the English
Channel on DC links, through which we buy the output of the French
nuclear power plats they build along their north coast, due to the
politics involved building them 25 miles further north in the UK.
> 50Hz local distribution system is purely historic and well entrenched
> but the transformer sizes could be substantially reduced with 400HZ. In
I don't think anyone cares about transformer size anything like to
the extent you seem to.
> the US, local transformers on a pole appear to be the norm in a lot of
> areas.
Well 120V doesn't go very far before the regulation has gone to pot.
> These would certainly be lighter at 400Hz. The 400 Hz suggestion
> comes from discussions with US engineers many years ago on which way
> would you go today if you could start again. I certainly like it. I
I think it's a non-starter.
--
Andrew Gabriel
big...@meeow.co.uk
> In article <d97hrt$bsr$1...@newsg4.svr.pol.co.uk>,
> Capitol <cap...@spamfree.freeserve.co.uk> writes:
> > 50Hz local distribution system is purely historic and well entrenched
> > but the transformer sizes could be substantially reduced with 400HZ.
> I don't think anyone cares about transformer size anything like to
> the extent you seem to.
Cost. It may not be much per item, but add all those small cost savings
up and it comes to 1 with a long string of 0s on the end. Savings on
all domestic transformer operated gear, from wall warts to stereos to
microwaves. Savings on all inductor fluorescent lights. Savingsd on
reservoir capacitors everywhere. Savings on motor caps and pf
correction caps. Etc.
If we were starting from scratch now, we could save a nice little pile
with 400Hz - or if the sync zone would not be big enough to cover UK,
maybe less, but high than 50.
Question: in this day of rf comms anad accurate time standards, why can
we not use one central standard to sync gens all across the country, or
anywhere as large as is wanted. It may have not been that way in 1900,
but accurate time standards are fairly trivial now.
> > the US, local transformers on a pole appear to be the norm in a lot of
> > areas.
> Well 120V doesn't go very far before the regulation has gone to pot.
> > These would certainly be lighter at 400Hz. The 400 Hz suggestion
> > comes from discussions with US engineers many years ago on which way
> > would you go today if you could start again. I certainly like it. I
> I think it's a non-starter.
It is now, because of all the 50 and 60Hz kit. Theres too much of it
that wont be replaced any decade soon.
And its not really practical to make everything 50/400 compatible for
the next half a century before switchover.
The noise issue would not (need to) be a problem. Appliances would have
a noise rating and probably legal requirements, just as they have
various other requirements and ratings.
NT
Andrew Gabriel
big...@meeow.co.uk writes:
> Andrew Gabriel wrote:
>> In article <d97hrt$bsr$1...@newsg4.svr.pol.co.uk>,
>> Capitol <cap...@spamfree.freeserve.co.uk> writes:
>
>> > 50Hz local distribution system is purely historic and well entrenched
>> > but the transformer sizes could be substantially reduced with 400HZ.
>
>> I don't think anyone cares about transformer size anything like to
>> the extent you seem to.
>
> Cost. It may not be much per item, but add all those small cost savings
> up and it comes to 1 with a long string of 0s on the end. Savings on
> all domestic transformer operated gear, from wall warts to stereos to
Wall warts are purchased in bulk for figures like 30p each, so they
must already cost less than this to manufacture, including the
transformer. Maybe you could knock 5p off the price of a wall wart?
> microwaves. Savings on all inductor fluorescent lights. Savingsd on
These are all going electronic anyway.
> reservoir capacitors everywhere. Savings on motor caps and pf
> correction caps. Etc.
>
> If we were starting from scratch now, we could save a nice little pile
> with 400Hz - or if the sync zone would not be big enough to cover UK,
> maybe less, but high than 50.
>
> Question: in this day of rf comms anad accurate time standards, why can
> we not use one central standard to sync gens all across the country, or
> anywhere as large as is wanted. It may have not been that way in 1900,
> but accurate time standards are fairly trivial now.
It's not a time standard problem, it's a transmission line problem.
The National Grid is a large transmission line, and different parts
of it will be at slightly different phase angles due to transmission
delays. Now that might not be an insurmountable problem if it was
just a long 1-dimensional line, but it's a complex 2-dimensional
mesh, and the problem rapidly becomes unsolvable as the mesh size
grows or the frequency increases. I don't know what the wave
propagation velocity is on the National Grid, but best case it's
the speed of light, so you have a 1/4 wavelength phase shift in
around 1000 miles. At 400Hz, you shrink the max length of a synch
zone to just 1/8th size, which is 1/64th of the area, so you need
64 times as many synchronisation zones and a collosal number of
expensive conversion stations to feed power between unsynch'ed zones.
>> > the US, local transformers on a pole appear to be the norm in a lot of
>> > areas.
>
>> Well 120V doesn't go very far before the regulation has gone to pot.
>
>> > These would certainly be lighter at 400Hz. The 400 Hz suggestion
>> > comes from discussions with US engineers many years ago on which way
>> > would you go today if you could start again. I certainly like it. I
>
>> I think it's a non-starter.
>
> It is now, because of all the 50 and 60Hz kit. Theres too much of it
> that wont be replaced any decade soon.
I don't think that's the only issue. Another one which just occurs
to me would be skin depth effect on large high current conductors;
not insurmountable, but you'd have to change the conductors to
multiple strands or flat tapes at 400Hz for smaller conductor sizes
than is required at 50Hz, which would make cables and terminations
more expensive.
All this to save 5p off the price of a wall wart? I have my doubts...
--
Andrew Gabriel
big...@meeow.co.uk
> big...@meeow.co.uk writes:
> >> Capitol <cap...@spamfree.freeserve.co.uk> writes:
> Wall warts are purchased in bulk for figures like 30p each, so they
> must already cost less than this to manufacture, including the
> transformer. Maybe you could knock 5p off the price of a wall wart?
400Hz means a wart small enough to fit into a high top mains plug in
many cases. It means a far smaller TF.
So lets say we cut from 30p to 20p each at the factory gates, or £2 to
£1.33 on the retail shelf.
Now, how many warts have you bought in total? Lets take a vague guess
at 10. Times 60 million people in UK gives us:
factory gates savings of £60 million
and consumer savings of £400 million.
And thats just for warts, which are definitely not the biggest saving.
> > microwaves. Savings on all inductor fluorescent lights. Savingsd on
> These are all going electronic anyway.
not microwaves. We might save £5-10 retail per nuke. Say £5, and say
a history of 5 nukes owned per person.
5 x 60 mill x £5 = £1.5 billion
Get the picture?
> > Question: in this day of rf comms anad accurate time standards, why can
> > we not use one central standard to sync gens all across the country, or
> > anywhere as large as is wanted. It may have not been that way in 1900,
> > but accurate time standards are fairly trivial now.
> It's not a time standard problem, it's a transmission line problem.
> The National Grid is a large transmission line, and different parts
> of it will be at slightly different phase angles due to transmission
> delays. Now that might not be an insurmountable problem if it was
> just a long 1-dimensional line, but it's a complex 2-dimensional
> mesh, and the problem rapidly becomes unsolvable as the mesh size
> grows or the frequency increases. I don't know what the wave
> propagation velocity is on the National Grid, but best case it's
> the speed of light, so you have a 1/4 wavelength phase shift in
> around 1000 miles. At 400Hz, you shrink the max length of a synch
> zone to just 1/8th size, which is 1/64th of the area, so you need
> 64 times as many synchronisation zones and a collosal number of
> expensive conversion stations to feed power between unsynch'ed zones.
OK, I'll rephrase the question: why can all gens not be synced by a
common time standard instead of by the neighbouring mains waveform?
> I don't think that's the only issue. Another one which just occurs
> to me would be skin depth effect on large high current conductors;
> not insurmountable, but you'd have to change the conductors to
> multiple strands or flat tapes at 400Hz for smaller conductor sizes
> than is required at 50Hz, which would make cables and terminations
> more expensive.
skin effect at 400Hz??
NT
John
<big...@meeow.co.uk> wrote in message
news:1119483533.3...@g47g2000cwa.googlegroups.com...
Andrew Gabriel wrote:
> big...@meeow.co.uk writes:
> >> Capitol <cap...@spamfree.freeserve.co.uk> writes:
OK, I'll rephrase the question: why can all gens not be synced by a
common time standard instead of by the neighbouring mains waveform?
Laws of physics - there are stupendous forces involved in trying to drag an
alternator out of synchronism once its locked in. I'd have to dig my old
student days books out of the loft to find the calcs but one of the examples
we studied on a 250MVA unit slipping by a factor of 0.1 astounded the whole
of our group. The synch restoring torque was massive
Tony Williams
John <bo1l...@ASbtinternet.com> wrote:
> OK, I'll rephrase the question: why can all gens not be synced by
> a common time standard instead of by the neighbouring mains
> waveform?
I think because there is the unavoidable problem
of phase shift along the transmission cables. The
wavelength of 50Hz is about 6000Km, at which the
phase would have shifted a full 360 degrees.
Sounds no problem, but that represents a 10 degree
sync difference only every 167Km or 104 miles.
That might cause a problem on the UK's grid.
--
Tony Williams.
Martin Angove
Tony Williams <to...@ledelec.demon.co.uk> wrote:
You mean that if generator "A" and generator "C" are each 100 miles away
from generator "B", are all synchronised together in *absolute* time by
an external reference and all supply the same line, the waveform
supplied by "A" and "C" will be 10 degrees out of phase with that
supplied by "B" as measured from "B".
A=====B=====C
Sounds nasty.
So am I right in thinking that the way it is actually done is
(effectively) to have one generator start first, and for each of the
others to synchronise with the received waveform at their own locations?
In other words the generators are, in absolute terms, out of phase with
each other but due to wavelength / propagation delay / whatever are
for all practical purposes synchronised.
I can see how this would work for a "bus" topology, but not for anything
involving either rings or a mesh as the length of two or more paths
from generator to generator will be different and hence received
waveforms from each one will be different. How is the grid/supergrid
actually organised in this country? How do they do it in the US where
distances are vastly greater?
Learn something new every day on this ng :-)
Hwyl!
M.
--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
... Scotty, I've fallen and I can't beam up!
Mike
"Martin Angove" <MJAn...@tridwr.demon.co.uk> wrote in message
news:43b550824...@tridwr.demon.co.uk...
> How do they do it in the US where distances are vastly greater?
I expect there is no true electricity supply sync across the US. It's
simply too big as you say.
Even for the phone network there are occasional clock slips where a bit is
lost or gained.
Tony Williams
Martin Angove <MJAn...@tridwr.demon.co.uk> wrote:
> You mean that if generator "A" and generator "C" are each 100
> miles away from generator "B", are all synchronised together in
> *absolute* time by an external reference and all supply the same
> line, the waveform supplied by "A" and "C" will be 10 degrees out
> of phase with that supplied by "B" as measured from "B".
> A=====B=====C
> Sounds nasty.
I probably have the numbers widely out, but all transmission
lines have a line wavelength, which is the line length over
which the phase lags by 360 degrees. It means that if a
sinewave is started at point A, then there is a delay before
before it starts at point B, etc. An effective phase shift.
> So am I right in thinking that the way it is actually done is
> (effectively) to have one generator start first, and for each of
> the others to synchronise with the received waveform at their own
> locations? In other words the generators are, in absolute terms,
> out of phase with each other but due to wavelength / propagation
> delay / whatever are for all practical purposes synchronised.
Apparently the re-start after New York's great Blackout
(some years ago now) was very difficult.
> I can see how this would work for a "bus" topology, but not for
> anything involving either rings or a mesh as the length of two or
> more paths from generator to generator will be different and
> hence received waveforms from each one will be different. How is
> the grid/supergrid actually organised in this country? How do
> they do it in the US where distances are vastly greater?
Not my field Martin, so I have no idea how the UK grid
works, nor if there are difficulties with interconnections.
Be interesting to know though.............
--
Tony Williams.
big...@meeow.co.uk
With a mesh, the UK is fairly narrow, so the phase shifts east-west
would be small compared to north-south, I guess.
In principle I imagine one could have no end of phase shift if, and
only if, something... ha, I cant explain it. But I guess its apparent
theres no limit to how much phase shift could be accomodated within a
network, but it would depend very much on its layout and current flows.
You'd have to be careful what you connected to what via what, but in
principle one could presumably operate a grid with a ripple shaped
phase shift, like a ripple in water, with the phase shift adding upto
several whole cycles.
Someone can now explain why this is total twaddle.
NT
Andy Hall
<datami...@datamix.com> wrote:
>On Sat, 18 Jun 2005 22:43:26 GMT, Chip <chipmu...@excite.com>
>wrote:
>
>>On Sat, 18 Jun 2005 22:58:54 +0100,it is alleged that "Mike"
>><mi...@nospam.com> spake thusly in uk.d-i-y:
>>
>>[snip]
>>
>>>I don't know what frequency (or voltage) he used but Tesla's company
>>>distributed AC mains in the US before it reached Europe.
>>
>>From http://en.wikipedia.org/wiki/Alternating_current , so it may be
>>inaccurate but sounds reasonable:
>>
>>"It is generally accepted that Nikola Tesla chose 60 hertz as the
>>lowest frequency that would not cause street lighting to flicker
>>visibly. The origin of the 50 hertz frequency used in other parts of
>>the world is open to debate but seems likely to be a rounding off of
>>60hz to the 1 2 5 10 structure popular with metric standards."
>>
>>
>>From my own knowledge I am fairly certain that a German company was
>>responsible for the usage of 50 Hz in Europe, it may have been
>>Siemens, but my memory is fallible :-)
>>
>>In any case, in a region like Europe, having a well established AC
>>system of one frequency in the area would tend to encourage the usage
>>of that frequency elsewhere to facilitate crossover of equipment and
>>appliances, thus leading to savings in various things I slept through
>>in economics class;-)
>
>I always assumed that 50hertz came about as a doubling of 25 hertz to
>reduce flicker and improve transformer efficiency.
>
>Also, 60 Cycles Per Second is the logical extension of 60 seconds in a
>minute, 60 minutes in a hour.
>
Sort of like 12 inches to a foot, three feet to a yard, 22 yards to a
chain, 8 chains to a furlong, Bush installing democracy in the Arab
world in an afternoon (whether they wanted it or not).... that type of
thing.
A logical progression......
--
.andy
To email, substitute .nospam with .gl
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com
Andy Hall
<datami...@datamix.com> wrote:
>On Tue, 28 Jun 2005 23:54:51 +0100, Martin Angove
><MJAn...@tridwr.demon.co.uk> wrote:
>
>>In message <4d8189e...@ledelec.demon.co.uk>,
>> Tony Williams <to...@ledelec.demon.co.uk> wrote:
>>
>>snip
>>
>>I can see how this would work for a "bus" topology, but not for anything
>>involving either rings or a mesh as the length of two or more paths
>>from generator to generator will be different and hence received
>>waveforms from each one will be different. How is the grid/supergrid
>>actually organised in this country? How do they do it in the US where
>>distances are vastly greater?
>
>The North American power grid consists of four major synchronous
>interconnect regions - Western, Eastern, Texas, and Quebec.
..... and New York. On good days at least.
Dave Plowman (News)
Jim Michaels <datami...@datamix.com> wrote:
> >In US IIUC it would be called 240v, but in fact be 120-0-120, so the
> >voltage from earth is 120 ac, not 240. In which case the fault
> >clearance benefit of genuinely 240v would sometimes apply and sometimes
> >not. Some faults that smoulder at 120 can arc over and trip at 240.
> And some that would not cause a fire at 120V will burst into flames at
> 240V.
Not so - it's the current that causes a fire. If low voltage was safer
from the fire point of view, cars would never suffer electrical fires.
--
*Many people quit looking for work when they find a job *
Andrew Gabriel
Jim Michaels <datami...@datamix.com> writes:
> On 18 Jun 2005 03:30:22 -0700, big...@meeow.co.uk wrote:
>
>>Jim Michaels wrote:
>>> Hi,
>>>
>>> I will assume that your post is not bait and is serious
>>
>>You make some good points, but there are a few I'll pick up on:
>>
>>
>>> On Wed, 1 Jun 2005 10:31:18 +0100, "Christian McArdle"
>>> <cmcar...@nospam.yahooxxxx.co.uk> wrote:
>>
>>> >The US electrical system is simply unsafe compared to the rest of the world.
>>
>>true, at least compared to UK. Maybe not the world, US seems the model
>>of good practice compared to African practices, and that of many other
>>countries.
>>
>>
>>> Current, of course). Edison's first great central station, supplying
>>> power for three thousand lamps, was erected at Holborn Viaduct,
>>> London, in 1882. Does anyone know the voltage that was used? In any
>>> case the U.S. Voltage is due to historical factors. I am sure the
>>> British voltage was not selected much more recently.
>>
>>but this doesnt change the fact that 110 is inherently more dangerous
>>than 240. With 240v we treat it with respect, with 110v people relax
>>since it wont electrocute them, and hurts waaay less if they get bit.
>>They worry less about cord grips etc. The result is fires, which are
>>the prime killer, not electrocution.
>>
>>
>>> >The basic issue is that
>>> >very few people die of electrocution, whilst loads of people die from
>>> >electrical fires. The electrical fires largely stem from high currents. If
>>> >you halve the voltage, you double the current.
>>> NOT TRUE.
>>> You are making multiple invalid assumptions.
>>> 1. That U.S. wiring has the same number of circuits for the same load.
>>
>>still cant figure out what you mean there. For a given load you do have
>>higher i with lower v, and each load is on 1 circuit as far as i can
>>see.
>
> UK Ten 100watt lamps at 240V equal 4.166 amps on circuit rated at 6
> amps with 1mm wire.
Although lighting circuits are normally protected at 6A, the 1mm²
wiring is actually rated at 12A. The lower value protection is
required because of the choice of lampholders on the circuits.
> US Five 100 watt lamps at 120V equals 4.166 amps on 15amp rated
> circuit with 14gauge (2.08mm) wire.
>
> In this example the US system has a massively greater safety margin.
Fires tend to start at wiring accessories, cable joins, etc,
and not so much in the middle of a length of wire.
>>
>>> 2. That U.S. circuits are not designed for their load.
>>
>>I dont think that was the assumption:
>
> The proof is that you keep saying "for a given load" and the loads are
> NOT the same, we have many more circuits in typical dwelling.
>
>> the problem is simply theyre
>>designed to have a higher incidence of faults.
>
> Simply a system with more smaller circuits each with an equal or
> greater degree of safety margin.
>
> As an example a modest 3 bedroom suburban home normally has a 200amp
> 40 way main panel (CU). That is 200amps in each leg of the incoming
> feed using three 85mm cables. this provides 48kW of power. This is a
> home with gas space heating, gas water heating, gas clothes drying,,
> and often gas cooking.
> Even with our maniacal excess it would be hard to overload such a
> system to the point of combustion.
Normal UK home has a 100A (24kW) supply.
If you want any more than this, you have to have a 3-phase supply,
but that's quite unusual in a home unless it was very big.
--
Andrew Gabriel
big...@meeow.co.uk
> On 18 Jun 2005 03:30:22 -0700, big...@meeow.co.uk wrote:
> >> >The basic issue is that
> >> >very few people die of electrocution, whilst loads of people die from
> >> >electrical fires. The electrical fires largely stem from high currents. If
> >> >you halve the voltage, you double the current.
> >> NOT TRUE.
> >> You are making multiple invalid assumptions.
> >> 1. That U.S. wiring has the same number of circuits for the same load.
> >still cant figure out what you mean there. For a given load you do have
> >higher i with lower v, and each load is on 1 circuit as far as i can
> >see.
> UK Ten 100watt lamps at 240V equal 4.166 amps on circuit rated at 6
> amps with 1mm wire.
>
> US Five 100 watt lamps at 120V equals 4.166 amps on 15amp rated
> circuit with 14gauge (2.08mm) wire.
>
> In this example the US system has a massively greater safety margin.
Your analysis is too simplistic. The load current / cable rating is not
something that causes any significant number of fires in either case,
it is a nonissue in reality.
Also I assume you realise 1mm2 is capable of much more than 6A, it is
merely fused at 5A or MCBed at 6A.
Safety margin is determined by looking at what in the system causes
safety failures, and how often. Cable rating doesnt come into it. Your
heavy US cables are merely a waste of resources, achieving nothing
afaics.
Unless you can explain how 4A on 32A capable cable tripped at 15A is
safer than 4A on 15A cable tripped at 6A. (figures are examples, not
calculated)
> >> 2. That U.S. circuits are not designed for their load.
> >I dont think that was the assumption:
> The proof is that you keep saying "for a given load" and the loads are
> NOT the same, we have many more circuits in typical dwelling.
to be honest I dont know what youre referring to, youve snipped the
relevant stuff out.
But I remember just enough to be fairly sure the assumption above didnt
come into it, that IIRC you misunderstood what was being said.
> > the problem is simply theyre
> >designed to have a higher incidence of faults.
> Simply a system with more smaller circuits each with an equal or
> greater degree of safety margin.
Youre not understanding safety margin. Size of cable has nothing to do
with it, once the cables big enough not to overload. Ours are big
enough and much more. Yours are even bigger, but for what? Its just
poor engineering.
> As an example a modest 3 bedroom suburban home normally has a 200amp
> 40 way main panel (CU). That is 200amps in each leg of the incoming
> feed using three 85mm cables.
Above ground supply or buried? 85mm2 is awful big, even for 200A. Or is
it aluminium?
> this provides 48kW of power. This is a
> home with gas space heating, gas water heating, gas clothes drying,,
> and often gas cooking.
> Even with our maniacal excess it would be hard to overload such a
> system to the point of combustion.
Again you miss it. Your systems are overloaded day in day out, not at
the service entrance but at the wall plugs that get too hot, and the
wirenuts that cant reliably maintain their ratings. The result is a
high level of fires.
> >The practice of push-in
> >connection on mains sockets is something considered unthinkable here,
> >for good reason.
>
> They are a homeowner/shoddy contractor item and are frowned upon.
precisely, here theyre illegal and unheard of. There isnt even a black
market in such junk, its just off the scale. Even the occasional 50
year old install isnt that bad.
> >In US IIUC it would be called 240v, but in fact be 120-0-120, so the
> >voltage from earth is 120 ac, not 240. In which case the fault
> >clearance benefit of genuinely 240v would sometimes apply and sometimes
> >not. Some faults that smoulder at 120 can arc over and trip at 240.
>
> And some that would not cause a fire at 120V will burst into flames at
> 240V.
yup. the question is which is the greater number. 240 gives much better
clearance rate than 120.
> >> >3. Combination of neutral to earth (i.e. effectively TN-C earthing) leading
> >> >to electrocution in the event of polarisation swap, or some open circuit
> >> >conditions.
> >
> >snip
>
> Why snip the explanation?
if you could quote all relevant material I might be able to answer.
NT
Andrew Gabriel
big...@meeow.co.uk writes:
>
> Youre not understanding safety margin. Size of cable has nothing to do
> with it, once the cables big enough not to overload. Ours are big
> enough and much more. Yours are even bigger, but for what? Its just
> poor engineering.
Because voltage drop is a serious issue for 120V supplies.
It's not for 240V supplies.
--
Andrew Gabriel
Capitol
big...@meeow.co.uk wrote:
Various wrote
>>>The practice of push-in
>>>connection on mains sockets is something considered unthinkable here,
>>>for good reason.
>>
>>They are a homeowner/shoddy contractor item and are frowned upon.
>
>
> precisely, here theyre illegal and unheard of. There isnt even a black
> market in such junk, its just off the scale. Even the occasional 50
> year old install isnt that bad.
>
Many new lighting fittings on sale in the UK today use push in
connections! Probably other connectors as well.
Regards
Capitol
Chip
spake thusly in uk.d-i-y:
[snip]
>Safety margin is determined by looking at what in the system causes
>safety failures, and how often. Cable rating doesnt come into it. Your
>heavy US cables are merely a waste of resources, achieving nothing
>afaics.
Dunno, they seem much sturdier against mechanical damage (stripping
etc).
>> As an example a modest 3 bedroom suburban home normally has a 200amp
>> 40 way main panel (CU). That is 200amps in each leg of the incoming
>> feed using three 85mm cables.
>
>Above ground supply or buried? 85mm2 is awful big, even for 200A. Or is
>it aluminium?
Generally Alumin(i)um wiring for the service entrance cables upto the
main breaker in the distribution panel.
[snip]
>Again you miss it. Your systems are overloaded day in day out, not at
>the service entrance but at the wall plugs that get too hot, and the
>wirenuts that cant reliably maintain their ratings. The result is a
>high level of fires.
Wall outlets and plugs don't get hot when they're new, it tends to be
the older ones that are loose that overheat. I never in 5 years in the
US saw wirenuts that couldn't maintain the ratings *when installed
correctly*.
Most fires are due to overloading extension cords, that is one thing
that really SHOULD be changed, they allow 13 amp rated (16AWG) ext
cords on 20 amp circuits, which is a recipe for disaster, one that all
too often works well:-(
>precisely, here theyre illegal and unheard of. There isnt even a black
>market in such junk, its just off the scale. Even the occasional 50
>year old install isnt that bad.
As someone else has noted, they are appearing on lighting equipment
and scare the bejesus out of me, the ones that are on light fixtures
make the US backstab connections look secure.
[much snippage]
Not trying to further the war:-) Just observations I made.
--
Computers achieved sentience in nineteen seventy five. The reason we're
unaware of this is that they watched TV, saw what we do to sentient
computers, and decided to take it out on us secretly. We call the
result of this descision "Windows"
big...@meeow.co.uk
> On 4 Jul 2005 11:11:49 -0700,it is alleged that big...@meeow.co.uk
> spake thusly in uk.d-i-y:
> >Safety margin is determined by looking at what in the system causes
> >safety failures, and how often. Cable rating doesnt come into it. Your
> >heavy US cables are merely a waste of resources, achieving nothing
> >afaics.
> Dunno, they seem much sturdier against mechanical damage (stripping
> etc).
is that one of the big causes of fires though?
> >Again you miss it. Your systems are overloaded day in day out, not at
> >the service entrance but at the wall plugs that get too hot, and the
> >wirenuts that cant reliably maintain their ratings. The result is a
> >high level of fires.
> Wall outlets and plugs don't get hot when they're new, it tends to be
> the older ones that are loose that overheat.
ok, so they are a problem.
> I never in 5 years in the
> US saw wirenuts that couldn't maintain the ratings *when installed
> correctly*.
If users routinely cant install them safely, even after over half a
century of use, theyre a safety problem. Whatever the mechanics of it,
they do cause fires, but are still used. Strips of 12 screw connectors
are very cheap here, even if not as cheap as wirenuts. The cost to save
those lives is trivial. Add in the great cost saved in damaged goods,
and the US's use of wirenuts seems to make no real sense.
> Most fires are due to overloading extension cords, that is one thing
> that really SHOULD be changed, they allow 13 amp rated (16AWG) ext
> cords on 20 amp circuits, which is a recipe for disaster, one that all
> too often works well:-(
why would that cause disaster, given the large cable safety margins?
and why permit 13A rated cable on 20A circuits?
If what youre saying is accurate, the next question is why.
> >precisely, here theyre illegal and unheard of. There isnt even a black
> >market in such junk, its just off the scale. Even the occasional 50
> >year old install isnt that bad.
> As someone else has noted, they are appearing on lighting equipment
> and scare the bejesus out of me, the ones that are on light fixtures
> make the US backstab connections look secure.
We use them only for low current apps in UK, for which they work
satisfactorily. Trying to put over 10A through them is another matter.
They will only maintain a gas tight connection over a very small
contact area.
NT
big...@meeow.co.uk
> On 4 Jul 2005 11:11:49 -0700,it is alleged that big...@meeow.co.uk
> spake thusly in uk.d-i-y:
> >Safety margin is determined by looking at what in the system causes
> >safety failures, and how often. Cable rating doesnt come into it. Your
> >heavy US cables are merely a waste of resources, achieving nothing
> >afaics.
> Dunno, they seem much sturdier against mechanical damage (stripping
> etc).
is that one of the big causes of fires though?
> >Again you miss it. Your systems are overloaded day in day out, not at
> >the service entrance but at the wall plugs that get too hot, and the
> >wirenuts that cant reliably maintain their ratings. The result is a
> >high level of fires.
> Wall outlets and plugs don't get hot when they're new, it tends to be
> the older ones that are loose that overheat.
ok, so they are a problem.
> I never in 5 years in the
> US saw wirenuts that couldn't maintain the ratings *when installed
> correctly*.
If users routinely cant install them safely, even after over half a
century of use, theyre a safety problem. Whatever the mechanics of it,
they do cause fires, but are still used. Strips of 12 screw connectors
are very cheap here, even if not as cheap as wirenuts. The cost to save
those lives is trivial. Add in the great cost saved in damaged goods,
and the US's use of wirenuts seems to make no real sense.
> Most fires are due to overloading extension cords, that is one thing
> that really SHOULD be changed, they allow 13 amp rated (16AWG) ext
> cords on 20 amp circuits, which is a recipe for disaster, one that all
> too often works well:-(
why would that cause disaster, given the large cable safety margins?
and why permit 13A rated cable on 20A circuits?
If what youre saying is accurate, the next question is why.
> >precisely, here theyre illegal and unheard of. There isnt even a black
> >market in such junk, its just off the scale. Even the occasional 50
> >year old install isnt that bad.
> As someone else has noted, they are appearing on lighting equipment
> and scare the bejesus out of me, the ones that are on light fixtures
> make the US backstab connections look secure.
We use them only for low current apps in UK, for which they work
Chip
spake thusly in uk.d-i-y:
[snip]
>> Dunno, they seem much sturdier against mechanical damage (stripping
>> etc).
>
>is that one of the big causes of fires though?
Through arcing faults if the cable breaks, it can be.
>
>> >Again you miss it. Your systems are overloaded day in day out, not at
>> >the service entrance but at the wall plugs that get too hot, and the
>> >wirenuts that cant reliably maintain their ratings. The result is a
>> >high level of fires.
>
>> Wall outlets and plugs don't get hot when they're new, it tends to be
>> the older ones that are loose that overheat.
>
>ok, so they are a problem.
Yes but I've seen the same with the fuse clips on 13 amp UK plugs.
Some makes seem to work loose, this is now mostly fixed. US socket
outlets had the same issues, which are now also mostly fixed.
>
>> I never in 5 years in the
>> US saw wirenuts that couldn't maintain the ratings *when installed
>> correctly*.
>
>If users routinely cant install them safely, even after over half a
>century of use, theyre a safety problem. Whatever the mechanics of it,
>they do cause fires, but are still used. Strips of 12 screw connectors
>are very cheap here, even if not as cheap as wirenuts. The cost to save
>those lives is trivial. Add in the great cost saved in damaged goods,
>and the US's use of wirenuts seems to make no real sense.
To be fair, I have seen strip connectors cause burn ups too,
personally I prefer wirenuts as being easier to install.
Many fires with wirenuts were caused by their use on Al cable, in a
few cases with UL approval. This caused and still causes a lot of
anger with US electricians who know from experience it doesn't work,
but nobody listens to them. Pretty much the same as here:-(
>
>> Most fires are due to overloading extension cords, that is one thing
>> that really SHOULD be changed, they allow 13 amp rated (16AWG) ext
>> cords on 20 amp circuits, which is a recipe for disaster, one that all
>> too often works well:-(
>
>why would that cause disaster, given the large cable safety margins?
Those safety margins are for fixed wiring cables, the fire usually
starts right where someone put the extension cord under a rug.
>
>and why permit 13A rated cable on 20A circuits?
>
>If what youre saying is accurate, the next question is why.
>
Indeed.
>
>> >precisely, here theyre illegal and unheard of. There isnt even a black
>> >market in such junk, its just off the scale. Even the occasional 50
>> >year old install isnt that bad.
>
>> As someone else has noted, they are appearing on lighting equipment
>> and scare the bejesus out of me, the ones that are on light fixtures
>> make the US backstab connections look secure.
>
>We use them only for low current apps in UK, for which they work
>satisfactorily. Trying to put over 10A through them is another matter.
>They will only maintain a gas tight connection over a very small
>contact area.
Germany and Austria use the 'Wago' brand push in connectors, these
seem to have VERY high contact pressure compared to the ones on
ballasts and lampholders, personally I'd trust them at ~16 amps.
I think we should agree to differ over which wiring system is 'best'
overall, my opinion would be 'neither, they were both designed by
committee, but each has strengths and weaknesses, surprisingly often
in the same areas'.
Brian {Hamilton Kelly}
<lp22c150rtpq7vn1r...@4ax.com>
datami...@datamix.com "Jim Michaels" wrote:
> On 18 Jun 2005 22:46:09 GMT, and...@cucumber.demon.co.uk (Andrew
> Gabriel) wrote:
[Andrew's article pre-dates when I first subscribed to this group, so I'm
piggy-backing on Jim's]
> >In article <d92307$t3c$1...@news8.svr.pol.co.uk>,
> > Capitol <cap...@spamfree.freeserve.co.uk> writes:
> >> distribution circuits and products without upgrading. If we were
> >> starting again today the world would probably settle for 230V @ 400 Hz,
> >> giving smaller ( &cheap) transformers without significantly increased
> >> losses.
> >
> >400Hz severely reduces the maximum area of a synchronisation zone,
> >which makes carrying power any distance very much more expensive.
> >Many of the 50Hz zones are close to their size limit now, so I
> >don't think anyone would think of distributing at any higher
> >frequency in Europe. It would be OK on a small isolated island.
> >400Hz isn't suitable for industrial motors either. Actually, supplies
> >to large commercial customers at 16 2/3rds Hz and 25Hz used to be
> >quite common as they much prefer a lower frequency for large motors.
> >Transformer size is really only an issue on planes and boats, which
> >often do use 400Hz.
A *lot* of military hardware, neither afloat nor airborne, uses 400Hz for
power distribution, not just to cut down on the mass of transformers, but
also on their bulk.
A radar system with which I spent many years (it was first designed, but
never built, to go with a Predictor and the Vickers 3.7in AA gun,
ca.1946, but not constructed until the early/mid 1950s, and to my certain
knowledge was still being used, in a different role, right through into
the 1990s) had more than five HUNDRED power transformers operating off
"400Hz mains". Each sub-system had its own transformers for valve
heaters, HT supplies to anodes, EHT to klystrons and magnetrons, etc.
(The 400Hz "mains" came from a motor-alternator set, running off 3ph 50Hz
[which came in our instance off the public supply, but "in the field"
could arise from a pair of 27.5kVA Meadows diesel alternators]. The
startup current at switch-on was sufficient to bend the needle on the
electricity board's engineer's tong ammeter, even though it was on the
400A range: he was there to investigate our complaints of insufficient
iron in the substation transformer ;-)
--
Brian {Hamilton Kelly} b...@dsl.co.uk
"Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu
le loisir de la faire plus courte."
Blaise Pascal, /Lettres Provinciales/, 1657
Andrew Gabriel
b...@dsl.co.uk (Brian {Hamilton Kelly}) writes:
> > On 18 Jun 2005 22:46:09 GMT, and...@cucumber.demon.co.uk (Andrew
> > Gabriel) wrote:
> > >Transformer size is really only an issue on planes and boats, which
> > >often do use 400Hz.
> A *lot* of military hardware, neither afloat nor airborne, uses 400Hz for
> power distribution, not just to cut down on the mass of transformers, but
> also on their bulk.
Well, perhaps I should have broadened it to say portable/transportable.
I also got some private feedback from someone who used to be in the supply
industry who said transformer size _is_ important to them -- they want
them big and heavy, so they can't be stolen ;-)
--
Andrew Gabriel
big...@meeow.co.uk
> On Mon, 04 Jul 2005 11:14:32 +0100, "Dave Plowman (News)"
> <da...@davenoise.co.uk> wrote:
>
> >In article <oh32c1he5fc4di4k8...@4ax.com>,
> > Jim Michaels <datami...@datamix.com> wrote:
> >Not so - it's the current that causes a fire.
> Actually it is the energy current times voltage.
>
> For a given fault twice the voltage equals twice the current!
No again. Faults are not normally ohmic. Higher v creates much higher
i, and of course higher v means lower i breakers... result is a big
difference in fire rates, favouring 240. 240 clears faults much better.
NT
big...@meeow.co.uk
big...@meeow.co.uk:
> >they do cause fires, but are still used. Strips of 12 screw connectors
> >are very cheap here, even if not as cheap as wirenuts. The cost to save
> >those lives is trivial. Add in the great cost saved in damaged goods,
> >and the US's use of wirenuts seems to make no real sense.
> To be fair, I have seen strip connectors cause burn ups too,
> personally I prefer wirenuts as being easier to install.
all components have a failure rate, the question is the comparative
rates.
> Many fires with wirenuts were caused by their use on Al cable, in a
> few cases with UL approval. This caused and still causes a lot of
> anger with US electricians who know from experience it doesn't work,
> but nobody listens to them. Pretty much the same as here:-(
I dont think we allow that here! I cant offhand think of any domestic
wiring sceanrio thats permitted in UK by the 16th but dangerous...
maybe you can. The death rate is remarkably low.
> >> Most fires are due to overloading extension cords, that is one thing
> >> that really SHOULD be changed, they allow 13 amp rated (16AWG) ext
> >> cords on 20 amp circuits, which is a recipe for disaster, one that all
> >> too often works well:-(
> >
> >why would that cause disaster, given the large cable safety margins?
>
> Those safety margins are for fixed wiring cables, the fire usually
> starts right where someone put the extension cord under a rug.
so why are cables with inadequate margins used? Our regs in UK are the
other way, very conservative.
> >and why permit 13A rated cable on 20A circuits?
> >
> >If what youre saying is accurate, the next question is why.
> Indeed.
> I think we should agree to differ over which wiring system is 'best'
> overall, my opinion would be 'neither, they were both designed by
> committee, but each has strengths and weaknesses, surprisingly often
> in the same areas'.
ok. I'll just compare the death rates.
NT
Chip
spake thusly in uk.d-i-y:
[snip]
>
>> Many fires with wirenuts were caused by their use on Al cable, in a
>> few cases with UL approval. This caused and still causes a lot of
>> anger with US electricians who know from experience it doesn't work,
>> but nobody listens to them. Pretty much the same as here:-(
>
>I dont think we allow that here! I cant offhand think of any domestic
>wiring sceanrio thats permitted in UK by the 16th but dangerous...
>maybe you can. The death rate is remarkably low.
[snip]
>ok. I'll just compare the death rates.
I think both of those come down to 'construction methods' rather than
wiring per se. A fire which in the UK will result in a smell of
hot/burned PVC then a call to an electrician as to why the breaker
keeps tripping now, would likely have burned down many homes in the US
with the all wood construction.
As to dangers, I think the dangers inherent with electricity often
mask other dangers.
As to wiring scenarios permitted but dangerous, to name a few we have
ring circuits, which allow the connection of 20A rated cable to a 30
amp circuit protective device. I know in practice they have proved
remarkably resilient, but they still give me the creeps. 1x 16A radial
per room, using 2.5mm cable with a _full size earth_ (none of this
cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
kitchen (on 4mm cable) would make me happier:-)
And 6amp lighting circuits with type B breakers, so that the lights on
the stairs go out at random (quite frequent) intervals is odd too.
--
This .signature has been hijacked by the Shellfish Liberation Army.
Please remain clam.
big...@meeow.co.uk
> On 6 Jul 2005 13:15:48 -0700,it is alleged that big...@meeow.co.uk:
> >I dont think we allow that here! I cant offhand think of any domestic
> >wiring sceanrio thats permitted in UK by the 16th but dangerous...
> >maybe you can. The death rate is remarkably low.
> [snip]
> >ok. I'll just compare the death rates.
> I think both of those come down to 'construction methods' rather than
> wiring per se. A fire which in the UK will result in a smell of
> hot/burned PVC then a call to an electrician as to why the breaker
> keeps tripping now, would likely have burned down many homes in the US
> with the all wood construction.
we have a lot of woodframe here as well, though brick is more popular.
> As to dangers, I think the dangers inherent with electricity often
> mask other dangers.
>
> As to wiring scenarios permitted but dangerous, to name a few we have
> ring circuits, which allow the connection of 20A rated cable to a 30
> amp circuit protective device. I know in practice they have proved
> remarkably resilient, but they still give me the creeps.
This has been covered in some depth on this ng recently. And the real
life stats bear it out: UK 30A rings are no danger at all.
> 1x 16A radial
> per room, using 2.5mm cable with a _full size earth_ (none of this
> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
> kitchen (on 4mm cable) would make me happier:-)
and increase death rates.
> And 6amp lighting circuits with type B breakers, so that the lights on
> the stairs go out at random (quite frequent) intervals is odd too.
yes, it is a bit. Type C gets recommended here, but Bs are still the
common choice.
So nothing dangerous.
NT
Chip
spake thusly in uk.d-i-y:
[snip]
>
>This has been covered in some depth on this ng recently.
I thought it had. (I came in at the tail end I believe).
>And the real
>life stats bear it out: UK 30A rings are no danger at all.
Indeed not, I just don't like them very much:-)
>> 1x 16A radial
>> per room, using 2.5mm cable with a _full size earth_ (none of this
>> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
>> kitchen (on 4mm cable) would make me happier:-)
>
>and increase death rates.
How would that increase death rates?
>
>> And 6amp lighting circuits with type B breakers, so that the lights on
>> the stairs go out at random (quite frequent) intervals is odd too.
>
>yes, it is a bit. Type C gets recommended here, but Bs are still the
>common choice.
Type C is good yes.
>
>So nothing dangerous.
>
I keep thinking "halfway down the stairs when the lights go out" or
"carrying a pan of boiling water across the kitchen"
--
You cannot shake hands with a clenched fist.
- Indira Gandhi
Dave Plowman (News)
Chip <chipmu...@excite.com> wrote:
> As to wiring scenarios permitted but dangerous, to name a few we have
> ring circuits, which allow the connection of 20A rated cable to a 30
> amp circuit protective device. I know in practice they have proved
> remarkably resilient, but they still give me the creeps. 1x 16A radial
> per room, using 2.5mm cable with a _full size earth_ (none of this
> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
> kitchen (on 4mm cable) would make me happier:-)
So you don't understand the principles of final ring circuits?
> And 6amp lighting circuits with type B breakers, so that the lights on
> the stairs go out at random (quite frequent) intervals is odd too.
Why would lights go out at random on the stairs?
--
*If I worked as much as others, I would do as little as they *
Chip
(News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
>In article <ljioc15v83mudhrnc...@news.virgin.net>,
> Chip <chipmu...@excite.com> wrote:
>> As to wiring scenarios permitted but dangerous, to name a few we have
>> ring circuits, which allow the connection of 20A rated cable to a 30
>> amp circuit protective device. I know in practice they have proved
>> remarkably resilient, but they still give me the creeps. 1x 16A radial
>> per room, using 2.5mm cable with a _full size earth_ (none of this
>> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
>> kitchen (on 4mm cable) would make me happier:-)
>
>So you don't understand the principles of final ring circuits?
Yes I understand the principle. I just don't *LIKE* the principle.
>
>> And 6amp lighting circuits with type B breakers, so that the lights on
>> the stairs go out at random (quite frequent) intervals is odd too.
>
>Why would lights go out at random on the stairs?
Because type B 6 amp breakers often trip whenever a lamp blows on the
circuit.
--
The follies which a man regrets most in his life are those
which he didn't commit when he had the opportunity.
- Helen Rowland
Andrew Gabriel
Chip <chipmu...@excite.com> writes:
> On Thu, 07 Jul 2005 00:00:28 +0100,it is alleged that "Dave Plowman
> (News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
>
>>In article <ljioc15v83mudhrnc...@news.virgin.net>,
>> Chip <chipmu...@excite.com> wrote:
>>> As to wiring scenarios permitted but dangerous, to name a few we have
>>> ring circuits, which allow the connection of 20A rated cable to a 30
>>> amp circuit protective device. I know in practice they have proved
>>> remarkably resilient, but they still give me the creeps. 1x 16A radial
>>> per room, using 2.5mm cable with a _full size earth_ (none of this
>>> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
>>> kitchen (on 4mm cable) would make me happier:-)
>>
>>So you don't understand the principles of final ring circuits?
>
> Yes I understand the principle. I just don't *LIKE* the principle.
You don't seem to understand why the CPC size can be reduced.
>>> And 6amp lighting circuits with type B breakers, so that the lights on
>>> the stairs go out at random (quite frequent) intervals is odd too.
>>
>>Why would lights go out at random on the stairs?
>
> Because type B 6 amp breakers often trip whenever a lamp blows on the
> circuit.
Still using mains filament lamps in 2005? It really is time to move on...
--
Andrew Gabriel
Chip
Gabriel) spake thusly in uk.d-i-y:
>In article <u6poc11ej14m807lr...@news.virgin.net>,
> Chip <chipmu...@excite.com> writes:
>> On Thu, 07 Jul 2005 00:00:28 +0100,it is alleged that "Dave Plowman
>> (News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
>>
>>>In article <ljioc15v83mudhrnc...@news.virgin.net>,
>>> Chip <chipmu...@excite.com> wrote:
>>>> As to wiring scenarios permitted but dangerous, to name a few we have
>>>> ring circuits, which allow the connection of 20A rated cable to a 30
>>>> amp circuit protective device. I know in practice they have proved
>>>> remarkably resilient, but they still give me the creeps. 1x 16A radial
>>>> per room, using 2.5mm cable with a _full size earth_ (none of this
>>>> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
>>>> kitchen (on 4mm cable) would make me happier:-)
>>>
>>>So you don't understand the principles of final ring circuits?
>>
>> Yes I understand the principle. I just don't *LIKE* the principle.
>
>You don't seem to understand why the CPC size can be reduced
You are correct, I don't see any circumstances where a reduced earth
conductor could be better than or even equal to a full size one.
>
>>>> And 6amp lighting circuits with type B breakers, so that the lights on
>>>> the stairs go out at random (quite frequent) intervals is odd too.
>>>
>>>Why would lights go out at random on the stairs?
>>
>> Because type B 6 amp breakers often trip whenever a lamp blows on the
>> circuit.
>
>Still using mains filament lamps in 2005? It really is time to move on..
So because someone else says they're old fashioned, the public should
be inconvenienced?
Andrew Gabriel
Chip <chipmu...@excite.com> writes:
> On 06 Jul 2005 23:37:41 GMT,it is alleged that andrew@a17 (Andrew
> Gabriel) spake thusly in uk.d-i-y:
>
>>In article <u6poc11ej14m807lr...@news.virgin.net>,
>> Chip <chipmu...@excite.com> writes:
>>> On Thu, 07 Jul 2005 00:00:28 +0100,it is alleged that "Dave Plowman
>>> (News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
>>>
>>>>In article <ljioc15v83mudhrnc...@news.virgin.net>,
>>>> Chip <chipmu...@excite.com> wrote:
>>>>> As to wiring scenarios permitted but dangerous, to name a few we have
>>>>> ring circuits, which allow the connection of 20A rated cable to a 30
>>>>> amp circuit protective device. I know in practice they have proved
>>>>> remarkably resilient, but they still give me the creeps. 1x 16A radial
>>>>> per room, using 2.5mm cable with a _full size earth_ (none of this
>>>>> cutdown 1.5mm earth in a 2.5 cable), maybe 2x20 amp radials for the
>>>>> kitchen (on 4mm cable) would make me happier:-)
>>>>
>>>>So you don't understand the principles of final ring circuits?
>>>
>>> Yes I understand the principle. I just don't *LIKE* the principle.
>>
>>You don't seem to understand why the CPC size can be reduced
>
> You are correct, I don't see any circumstances where a reduced earth
> conductor could be better than or even equal to a full size one.
OK then, please think of some likely scenario in which it is undersized.
>>>>> And 6amp lighting circuits with type B breakers, so that the lights on
>>>>> the stairs go out at random (quite frequent) intervals is odd too.
>>>>
>>>>Why would lights go out at random on the stairs?
>>>
>>> Because type B 6 amp breakers often trip whenever a lamp blows on the
>>> circuit.
>>
>>Still using mains filament lamps in 2005? It really is time to move on..
>
> So because someone else says they're old fashioned, the public should
> be inconvenienced?
Well, when I replace a CU, I don't use a B6 breaker on the lights.
That's largely a question of how competent a designer your electrician
is.
In my own home, I don't have any mains filament lamps indoors that
I can think of at the moment, at least, none on the lighting circuit.
I do have a couple of halogen ones outdoors, but they are on their
own breaker.
--
Andrew Gabriel
Andrew Gabriel
Jim Michaels <datami...@datamix.com> writes:
> On 04 Jul 2005 18:17:37 GMT, and...@cucumber.demon.co.uk (Andrew
Nope -- you require regulation mostly at the 120V level.
--
Andrew Gabriel
:::Jerry::::
"Andrew Gabriel" <andrew@a17> wrote in message
news:42cc6b45$0$38043$5a6a...@news.aaisp.net.uk...<snip>
> >
> > Because type B 6 amp breakers often trip whenever a lamp blows on
the
> > circuit.
>
> Still using mains filament lamps in 2005? It really is time to move
on...
>
Why?
Dave Plowman (News)
Chip <chipmu...@excite.com> wrote:
> >> And 6amp lighting circuits with type B breakers, so that the lights
> >> on the stairs go out at random (quite frequent) intervals is odd too.
> >
> >yes, it is a bit. Type C gets recommended here, but Bs are still the
> >common choice.
> Type C is good yes.
> >
> >So nothing dangerous.
> >
> I keep thinking "halfway down the stairs when the lights go out" or
> "carrying a pan of boiling water across the kitchen"
But given the frequency of power cuts in the US you'd have automatic
emergency lighting anyway?
--
*I have a degree in liberal arts -- do you want fries with that
Owain
>>>And 6amp lighting circuits with type B breakers, so that the lights on
>>>the stairs go out at random (quite frequent) intervals is odd too.
>>yes, it is a bit. Type C gets recommended here, but Bs are still the
>>common choice.
> Type C is good yes.
I've never had an MCB trip "randomly" or even on a bulb blow.
>>So nothing dangerous.
> I keep thinking "halfway down the stairs when the lights go out" or
> "carrying a pan of boiling water across the kitchen"
That is why I have an emergency lighting unit in the
kitchen-dinette-study-lounge.
Owain
Chip
(News)" <da...@davenoise.co.uk> spake thusly in uk.d-i-y:
[snip]
>> I keep thinking "halfway down the stairs when the lights go out" or
>> "carrying a pan of boiling water across the kitchen"
>
>But given the frequency of power cuts in the US you'd have automatic
>emergency lighting anyway?
Seems reasonable yes, the frequency of power cuts *is* much higher in
the US, but emergency lighting's a good idea anywhere.
--
We are just an advanced breed of monkeys on a minor planet of a very
average star. But we can understand the Universe. That makes us something
very special.
- Stephen Hawking
Chip
Gabriel) spake thusly in uk.d-i-y:
>> You are correct, I don't see any circumstances where a reduced earth
>> conductor could be better than or even equal to a full size one.
>
>OK then, please think of some likely scenario in which it is undersized.
I just don't like the concept of the protective conductor being a
smaller size than the line conductors potentially feeding fault
current into it.
[snip]
>> So because someone else says they're old fashioned, the public should
>> be inconvenienced?
>
>Well, when I replace a CU, I don't use a B6 breaker on the lights.
>That's largely a question of how competent a designer your electrician
>is.
Sadly most are not 'designers' at all, they install a B6 because
everyone uses 6amp for lighting, and if they just ask for a 6 amp
breaker, a type 'B' is what they get.
>
>In my own home, I don't have any mains filament lamps indoors that
>I can think of at the moment, at least, none on the lighting circuit.
>I do have a couple of halogen ones outdoors, but they are on their
>own breaker.
To be fair we have mostly compact fluorescents. It's just the
chandelier fitting in the living room which looks awful with anything
but 25w candle bulbs, and the GU10 Halogens in the conservatory. I am
intending to switch the GU10's to an FCU off the ring, but it's the
candle bulbs that do the breaker tripping (possibly due to smaller
lead spacing inside the lamps causing the plasma effect suggested
elsewhere).
--
SMS: Abbreviation, multiple meanings-
[1] Short Message Service, cellular telephone messaging method.
[2] SigMonster Sentience, when your sigmonster posts quotes about
sigmonsters.
Dave Plowman (News)
Chip <chipmu...@excite.com> wrote:
> >> I keep thinking "halfway down the stairs when the lights go out" or
> >> "carrying a pan of boiling water across the kitchen"
> >
> >But given the frequency of power cuts in the US you'd have automatic
> >emergency lighting anyway?
> Seems reasonable yes, the frequency of power cuts *is* much higher in
> the US, but emergency lighting's a good idea anywhere.
In my kitchen, the extractor hood lighting is on a separate circuit to
other lighting, and when cooking it's always on. So even if a bulb blowing
*did* trip an MCB, it would not plunge the room into darkness.
Same with stair lighting - it's on two circuits. But I think I'd find my
way downstairs ok in the dark. ;-)
--
*I'll try being nicer if you'll try being smarter
big...@meeow.co.uk
> On 4 Jul 2005 11:11:49 -0700, big...@meeow.co.uk wrote:
> >> UK Ten 100watt lamps at 240V equal 4.166 amps on circuit rated at 6
> >> amps with 1mm wire.
> >>
> >> US Five 100 watt lamps at 120V equals 4.166 amps on 15amp rated
> >> circuit with 14gauge (2.08mm) wire.
> >>
> >> In this example the US system has a massively greater safety margin.
> >
> >Your analysis is too simplistic. The load current / cable rating is not
> >something that causes any significant number of fires in either case,
> >it is a nonissue in reality.
>
> Agreed, There are not many electrical fires due to fixed wiring.
that is not correct.
> >Also I assume you realise 1mm2 is capable of much more than 6A, it is
> >merely fused at 5A or MCBed at 6A.
> >
> >Safety margin is determined by looking at what in the system causes
> >safety failures, and how often. Cable rating doesnt come into it. Your
> >heavy US cables are merely a waste of resources, achieving nothing
> >afaics.
>
> Just a reasonable engineering safety margin.
reasonable safety margin on wire sizes has been addrssed already. I
cant help thinking youre perhaps not keeping up.
> >> > the problem is simply theyre
> >> >designed to have a higher incidence of faults.
> Ridiculous.
hardly, look at the stats, and the practices that are known to cause
fires. Or dont.
> We may have more old or poorly maintained installations but safety has
> always been a primary concern.
Given what we've read in this thread, that conclusion is simply
impossible to draw.
> >> Simply a system with more smaller circuits each with an equal or
> >> greater degree of safety margin.
> >
> >Youre not understanding safety margin. Size of cable has nothing to do
> >with it, once the cables big enough not to overload. Ours are big
> >enough and much more. Yours are even bigger, but for what? Its just
> >poor engineering.
> Look up safety margin.
That doesnt answer the q at all. Im perfectly familiar with safety
margins, and UK has more than big enough margins in its cable sizes. US
cables are not large for that reason.
> >> this provides 48kW of power. This is a
> >> home with gas space heating, gas water heating, gas clothes drying,,
> >> and often gas cooking.
> >> Even with our maniacal excess it would be hard to overload such a
> >> system to the point of combustion.
> >
> >Again you miss it. Your systems are overloaded day in day out, not at
> >the service entrance but at the wall plugs that get too hot,
> ???????
thats news?
> > and the
> >wirenuts that cant reliably maintain their ratings.
> ???????
>
> >The result is a
> >high level of fires.
> ???????
thats news too??
I think time to end this discussion. Good luck.
NT
Andy Wade
> I just don't like the concept of the protective conductor being a
> smaller size than the line conductors potentially feeding fault
> current into it.
There's no logic to that. Protective conductors only have to be sized
to withstand the earth fault current for the time it takes to clear the
fault. Live conductors [1] have be able to withstand continuous
full-load design current as well as (where relevant) occasional
short-term overloads. The principle of using 'undersized' CPCs is very
well established, both in theory and practice, and has been so for a
very long time. The practice doesn't compromise safety; in fact it
avoids over-engineering and saves copper.
For live conductors of up to and including 16mm^2, BS 7671 requires the
designer to check the sizing of any intended under-size CPC using the
adiabatic equation (see Reg. 543-01-03) [2]. However, for twin & earth
cables, detailed calculation can be avoided by using the pre-calculated
final circuits given in Table 7.1 of the On-Site Guide (OSG). Provided
that you don't exceed the circuit lengths given in that table, for the
relevant type of protective device, type of earthing and required
disconnection time, and provided that the earth fault loop impedance
tests out OK (see Appendix 2 of the OSG) then your design and
installation should be safe from this POV.
If you scan through Table 7.1 you'll see that most circuits are
voltage-drop-limited, so a larger CPC will confer no advantage in terms
of allowable circuit length. Circuits where the length is limited by Zs
could be stretched by using a full-size CPC, but that rules out using
T&E cable, unless a separate CPC is run.
[1] This term means the current carrying conductors and therefore
includes any neutral.
[2] For 25 and 35mm^2 live conductors a 16mm^2 CPC can be used without
calculation; for larger sizes calculation is only required if the CPC is
less that one half of the live conductor size [BS7671 Table 54G].
--
Andy
Christian McArdle
> voltage-drop-limited, so a larger CPC will confer no advantage in terms
> of allowable circuit length.
The old style 2.5mm cable certainly used to be earth loop impedence limited
in many circumstances, which is why the CPC was increased to 1.5mm, to
enable longer circuits. As you suggest, there was no need to go larger, as
voltage drop becomes the dominant limit to circuit length.
Christian.
Chip
<spamb...@ajwade.clara.co.uk> spake thusly in uk.d-i-y:
>Chip wrote:
>
>> I just don't like the concept of the protective conductor being a
>> smaller size than the line conductors potentially feeding fault
>> current into it.
>
>There's no logic to that. Protective conductors only have to be sized
>to withstand the earth fault current for the time it takes to clear the
>fault.
That is where I have issues with the concept, I admit my calculations
verge on the 'worst case scenario' but a 1.5xI(n) fault would not blow
a 30 amp rewireable fuse in under a few minutes, and 45 amps flowing
through 2x1.5mm earth wires seems a generally bad idea to me. I am at
odds with the IEE and the prevailing opinion on this NG for that, and
the worst case is highly unlikely to happen, but I DO overengineer
wiring systems, for example I won't use 1.0mm2 cable, I use 1.5,
always, as the cost difference is minimal. I see no negative safety
implication of oversizing things compared to 'what is allowed'.
One of the things I am looking for is evidence of what is 'unsafe', so
I can avoid doing it :-)
> Live conductors [1] have be able to withstand continuous
>full-load design current as well as (where relevant) occasional
>short-term overloads. The principle of using 'undersized' CPCs is very
>well established, both in theory and practice, and has been so for a
>very long time. The practice doesn't compromise safety; in fact it
>avoids over-engineering and saves copper.
I think the differences are not as major as people at first think, in
the US the neutral on the drop (TN-C-S system before the split) is
often slightly undersized, they just don't extend it to final branch
circuits, we in the UK do, and many other european countries disagree
with this practice.
The saving in copper is minimal, and copper can be (and is) recycled
after the cable reaches the end of its useful life.
A small 'anachronism' is that if wiring in conduit, you use full size
earth conductors AND bond the conduit, which nobody feels is
overengineering, and with MI cable, the sheath is several times the
CSA of the conductors.
>
>For live conductors of up to and including 16mm^2, BS 7671 requires the
>designer to check the sizing of any intended under-size CPC using the
>adiabatic equation (see Reg. 543-01-03) [2]. However, for twin & earth
>cables, detailed calculation can be avoided by using the pre-calculated
>final circuits given in Table 7.1 of the On-Site Guide (OSG). Provided
>that you don't exceed the circuit lengths given in that table, for the
>relevant type of protective device, type of earthing and required
>disconnection time, and provided that the earth fault loop impedance
>tests out OK (see Appendix 2 of the OSG) then your design and
>installation should be safe from this POV.
>
>If you scan through Table 7.1 you'll see that most circuits are
>voltage-drop-limited, so a larger CPC will confer no advantage in terms
>of allowable circuit length. Circuits where the length is limited by Zs
>could be stretched by using a full-size CPC, but that rules out using
>T&E cable, unless a separate CPC is run.
>
>
>[1] This term means the current carrying conductors and therefore
>includes any neutral.
>
>[2] For 25 and 35mm^2 live conductors a 16mm^2 CPC can be used without
>calculation; for larger sizes calculation is only required if the CPC is
>less that one half of the live conductor size [BS7671 Table 54G].
In short, I am not saying the 'UK ring circuits are dangerous' but
more that 'under certain circumstances I can see that different
arrangements could be safer'. It's all a matter of degrees I guess.
--
"The perfect computer has been developed. You just feed in your problems
and they never come out again."
- Al Goodman.
Andrew Gabriel
Chip <chipmu...@excite.com> writes:
> On Thu, 07 Jul 2005 17:25:28 +0100,it is alleged that Andy Wade
> <spamb...@ajwade.clara.co.uk> spake thusly in uk.d-i-y:
>
>>Chip wrote:
>>
>>> I just don't like the concept of the protective conductor being a
>>> smaller size than the line conductors potentially feeding fault
>>> current into it.
>>
>>There's no logic to that. Protective conductors only have to be sized
>>to withstand the earth fault current for the time it takes to clear the
>>fault.
>
> That is where I have issues with the concept, I admit my calculations
> verge on the 'worst case scenario' but a 1.5xI(n) fault would not blow
> a 30 amp rewireable fuse in under a few minutes, and 45 amps flowing
> through 2x1.5mm earth wires seems a generally bad idea to me. I am at
45 amps will be generating some 10kW at the scene of the fault.
It would be pretty impossible to even deliberately engineer such
a fault which lasted more than a few seconds, without it either
shorting completely or blowing itself out into an open circuit.
The generation of 10kW will change the nature of a fault site
very quickly.
There just aren't credible scenarios where large currents flow
for an extended period in the earth conductor.
>> Live conductors [1] have be able to withstand continuous
>>full-load design current as well as (where relevant) occasional
>>short-term overloads. The principle of using 'undersized' CPCs is very
>>well established, both in theory and practice, and has been so for a
>>very long time. The practice doesn't compromise safety; in fact it
>>avoids over-engineering and saves copper.
>
> I think the differences are not as major as people at first think, in
> the US the neutral on the drop (TN-C-S system before the split) is
> often slightly undersized, they just don't extend it to final branch
> circuits, we in the UK do, and many other european countries disagree
> with this practice.
On a fully loaded US system, the neutral current is zero.
Same is true of a fully loaded 3-phase system in UK, which
is why 4-wire 3-phase circuits do sometimes have reduced
size neutrals (need to watch out for 3rd-harmonic components
though, which do add in the neutral rather than cancel out).
--
Andrew Gabriel
Chip
and...@cucumber.demon.co.uk (Andrew Gabriel) spake thusly in uk.d-i-y:
>45 amps will be generating some 10kW at the scene of the fault.
>It would be pretty impossible to even deliberately engineer such
>a fault which lasted more than a few seconds, without it either
>shorting completely or blowing itself out into an open circuit.
>The generation of 10kW will change the nature of a fault site
>very quickly.
>
>There just aren't credible scenarios where large currents flow
>for an extended period in the earth conductor.
>
Fair point :-)
>
>On a fully loaded US system, the neutral current is zero.
>Same is true of a fully loaded 3-phase system in UK, which
>is why 4-wire 3-phase circuits do sometimes have reduced
>size neutrals (need to watch out for 3rd-harmonic components
>though, which do add in the neutral rather than cancel out).
Yep, many people in the US are now being caught out by needing larger
size neutrals than phase conductors, especially in IT rich
environments such as office space etc, where the PC and IT equipment
PSUs generate nasty harmonics and cause local overheating of the
neutrals, not good.
--
I have left orders to be awakened at any time in case of national emergency,
even if I'm in a cabinet meeting.
- Ronald Reagan
Martin Angove
and...@cucumber.demon.co.uk (Andrew Gabriel) wrote:
> In article <20050705.23...@dsl.co.uk>,
> b...@dsl.co.uk (Brian {Hamilton Kelly}) writes:
> > > On 18 Jun 2005 22:46:09 GMT, and...@cucumber.demon.co.uk (Andrew
> > > Gabriel) wrote:
> > > >Transformer size is really only an issue on planes and boats, which
> > > >often do use 400Hz.
>
> > A *lot* of military hardware, neither afloat nor airborne, uses 400Hz for
> > power distribution, not just to cut down on the mass of transformers, but
> > also on their bulk.
>
> Well, perhaps I should have broadened it to say portable/transportable.
>
> I also got some private feedback from someone who used to be in the supply
> industry who said transformer size _is_ important to them -- they want
> them big and heavy, so they can't be stolen ;-)
>
Didn't stop someone stealing a 75MVA (? might be a factor out there, it
was a few years ago) transfromer from the ex-steelworks at
Templeborough. When British Steel handed the building over to the group
which turned it into the Magna Science Adventure Centre (I worked there
for a while) they left the last arc furnace transformer parked in the
lot while they found somewhere to put it.
No-one knows what happened to it, and it must have involved a large
crane and a low-loader, but when they came to claim it just before the
centre opened it was no longer there. Magna ended up paying a lot of
money to BS for having "lost" their transformer.
Hwyl!
M.
--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
... My other neighbour is quiet.
big...@meeow.co.uk
bit hard to resell that one...
NT