Is an RCBO an adequate replacement for an isolator?
Sidney Endon-Lee
admit that my electrical skills are not up to it, and I probably don't
have all the necessary test kit, both of which are a shame.
Anyway, a local firm has scented an opportunity (all the places on the
same development have the same, old, consumer unit) and have sent
round a fuzzy before and after picture of what replacing with a new
RCBO based unit would look like, and estimated a standard price, with
an addition if you need more 'ways'.
Anyway, it looks, from the picture, as though they'd remove isolating
switches and seem to have a design that has:
a) an RCBO per way; and
b) an RCBO acting as a 'main fuse', sized to be 'equivalent to' the
current main fuse.
Hence the question in my title. Is an RCBO a suitable isolator? And is
the rest of the design sensible? I can't tell from the text, or the
fuzzy picture, but I would assume that the RCBOs per way would be fast
acting, and the 'main fuse' replacement would be slow acting -
otherwise a nuisance trip could take out the whole board, which is
what I though we were trying to move away from.
If the supply is rated at 60A, is that what they would propose for the
'main fuse' equivalent? My understanding is that RCBOs (and MCBs) are
less 'forgiving' of overcurrents than fuses, so I'd actually lose some
peak capacity (not that I use it, but some might).
Of course, I can put the same questions to the firm that put the flyer
through the letterboxes, but I'd prefer some independent opinion
first, if that's possible. Thanks!
Sid
cynic
Are you sure about the "main fuse" being an RCBO? A double pole RCD
would be more the expected item and to provide discrimination would
need to be time delayed. Otherwise any significant earth fault on any
circuit would trip that cicuits 30mA RCBO "and" the main RCD cutting
power to the whole house.
The use of a 100mA typa S, time delayed RCD as main switch or isolator
is perfectly acceptable. It does beg the question why you think you
need to replace your original consumer unit apart from cosmetic
reasons do you have any genuine concerns about your installation?
I'll bet the firm will also be hoping to pick up on all sorts of extra
works based on things they "find" once they get started.
Dave Plowman (News)
<cd2f9fe2-e29e-42c7...@g27g2000yqn.googlegroups.com>,
Sidney Endon-Lee <unop...@mail.com> wrote:
> Of course, I can put the same questions to the firm that put the flyer
> through the letterboxes, but I'd prefer some independent opinion
> first, if that's possible. Thanks!
17th edition CUs have a conventional 2 pole main isolator switch and two
RCDs feeding a busbar each. On those busbars you have a choice of using
MCBs or RCBOs.
As a general point I'd be wary of using a firm just on the basis of a
flier. Unless neighbours have already used them and can vouch for their
work.
--
*Why don't sheep shrink when it rains?
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
Tim W
wibbled on Wednesday 11 November 2009 10:10
> I'm looking at replacing a somewhat old consumer unit. I'll freely
> admit that my electrical skills are not up to it, and I probably don't
> have all the necessary test kit, both of which are a shame.
>
> Anyway, a local firm has scented an opportunity (all the places on the
> same development have the same, old, consumer unit) and have sent
> round a fuzzy before and after picture of what replacing with a new
> RCBO based unit would look like, and estimated a standard price, with
> an addition if you need more 'ways'.
>
> Anyway, it looks, from the picture, as though they'd remove isolating
> switches and seem to have a design that has:
>
> a) an RCBO per way; and
Which provides the same level of isolation as the MCB that might be there in
a different, but complaint, installation.
> b) an RCBO acting as a 'main fuse', sized to be 'equivalent to' the
> current main fuse.
Your "main fuse" is the one in the elect co's cutout, typically near and
definately before the meter.
A time delayed (type S) RCD may be used in place of the main CU isolator, or
before it in a separate box, if you have a TT (earth rod) installation
earth. This is not and RCBO - it doesn't deal with current overloads and it
doesn't need to, any more than the main 100A switch in a CU would. The
supplier's fuse does that.
You could also have a non delatey 100A RCD - but this would be essentially
stupid along with RCBOs.
> Hence the question in my title. Is an RCBO a suitable isolator?
As much as any equivalent device that might be used is. It will typically
only isolate L and not N (although I have two double pole RCBOs that do
isolate L+N for outside circuits, because it seemed like a good idea,
though beyond basic requirements).
This means that you should not use the RCBO to act as eg as a shower
isolator - you still need the local DP switch. But in every other respect,
the RCBO is a complete replacement for and MCB or fuse.
> And is
> the rest of the design sensible? I can't tell from the text, or the
> fuzzy picture, but I would assume that the RCBOs per way would be fast
> acting,
Yes - 30mA earth leakage trip in less than 40mS IIRC - same as any normal
domestic RCD. The current overload curves will be as fast or faster than a
typical domestic fuse and typically the same as an MCB (note there are
different curves, B, C and D: B is typical in domestic and C is
occasionally found,being a bit "slower").
> and the 'main fuse' replacement would be slow acting -
Yes - in respect of the RCD trip time. The local per circuit RCBOs should
trip first and not this unit. The only way this should happen is if the
combined earth leakage is high enough but the contributing components are
too low to trip the local RCBO; or if the fault is between the RCD and
RCBOs.
> otherwise a nuisance trip could take out the whole board, which is
> what I though we were trying to move away from.
Exactly. But do you need the main RCD? Is the place TT earthed - or are they
proposing a split board with the RCD protecting a few random circuits and
the RCBOs bypassing the RCD? In which case the main RCD should also be
30mA/40mS.
> If the supply is rated at 60A, is that what they would propose for the
> 'main fuse' equivalent? My understanding is that RCBOs (and MCBs) are
> less 'forgiving' of overcurrents than fuses, so I'd actually lose some
> peak capacity (not that I use it, but some might).
Not relevant as the main RCD doesn't do overcurrent protection.
> Of course, I can put the same questions to the firm that put the flyer
> through the letterboxes, but I'd prefer some independent opinion
> first, if that's possible. Thanks!
I'd be wary of responding to a random flyer. If you want the work done, you
might be better getting another quote or two. OTOH, the company *may* be
genuine and you *may* benefit from them doing a bunch of identical work in
the same area (which is obviously of benefit to them too).
HTH
Tim
--
Tim Watts
This space intentionally left blank...
John Rumm
> Anyway, it looks, from the picture, as though they'd remove isolating
> switches and seem to have a design that has:
Remove which isolating switches?
> a) an RCBO per way; and
Fair enough...
> b) an RCBO acting as a 'main fuse', sized to be 'equivalent to' the
> current main fuse.
This bit does not sounds quite "right"...
Assuming you have :
1) A main cutout (traditionally a 60A or 100A fuse on the suppliers side
of the meter), tails from these feed the meter.
2) Tails from the meter then either feed the consumer unit directly, or
possibly via an isolating switch (and on complex or augmented
installations, there may be other CUs fed from tails split in a junction
box)
3) A CU which would normally have a main switch of its own (or perhaps a
main RCD acting as a switch), followed by a number of circuit breakers
or fuses.
I would expect a RCBO based replacement would be the same up as far as
the CU, and then the CU would have an ordinary main switch, followed by
RCBOs for each circuit.
Its not clear from your description if the "local development" is a
collection of independent houses etc or a multi occupancy building. With
the latter the "suppliers" side of the meter may well belong to the
freeholder rather than the supplier, and hence replacing the main cutout
with a MCB would be more plausible.
> Hence the question in my title. Is an RCBO a suitable isolator? And is
Generally no, since most modern (slim) RCBOs are single pole devices,
and hence don't isolate in the true sense. You can get double pole RCBOs
(usually double width modules). In the occasions where you would want
RCD functionality in the main switch location, you would probably not
want the overcurrent protection of a RCBO. Also you don't normally
cascade RCBOs (especially since time delayed RCBOs are somewhat rare)
> the rest of the design sensible? I can't tell from the text, or the
> fuzzy picture, but I would assume that the RCBOs per way would be fast
> acting, and the 'main fuse' replacement would be slow acting -
> otherwise a nuisance trip could take out the whole board, which is
> what I though we were trying to move away from.
>
> If the supply is rated at 60A, is that what they would propose for the
> 'main fuse' equivalent? My understanding is that RCBOs (and MCBs) are
> less 'forgiving' of overcurrents than fuses, so I'd actually lose some
> peak capacity (not that I use it, but some might).
MCB etc are actually very forgiving of over currents, but tend to be
faster on fault currents. (loading a 32A circuit to 40A for 20 mins is
an over current, nailing through a cable creating a short circuit
passing 800A is a fault current). So I would not see that as a
particular down side as long as the device is sized suitably to
discriminate with any of its downstream circuits.
> Of course, I can put the same questions to the firm that put the flyer
> through the letterboxes, but I'd prefer some independent opinion
> first, if that's possible. Thanks!
>
> Sid
>
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Doctor Drivel
"Tim W" <t...@dionic.net> wrote in message
news:hde6gn$4ln$1...@news.eternal-september.org...
An RCBO can eliminate equipotential bonding in bathrooms. I believe the
lights and power all have to be off the same RCBO.
Doctor Drivel
> A time delayed (type S) RCD may be used in place of the main CU isolator,
> or
> before it in a separate box, if you have a TT (earth rod) installation
> earth. This is not and RCBO - it doesn't deal with current overloads and
> it
> doesn't need to, any more than the main 100A switch in a CU would. The
> supplier's fuse does that.
>
> You could also have a non delatey 100A RCD - but this would be essentially
> stupid along with RCBOs.
Why would you want a main RCD if you have double pole RCBOs on all circuits?
I can't see the need for an RCD in this situation.
Sidney Endon-Lee
couple of things up
My place is one of a large development of purpose-built flats, built
by the GLC in the 1970s. They all have Wylex rewireable fuses in the
consumer unit, which has a 60A incomer. When I moved in, there was
still an original GLC card of fuse-wire in the cupboard with the
consumer unit. I've not had to use any of it myself, other than for an
electrician to add another 'way' to correct a d-i-y bodge I found in
the kitchen (unfused spur off a socket with three sockets off the
single ring, said spur providing power for the dishwasher, washer/
drier, and sink waste-disposal unit, with a Fridge/freezer plugged
into the ring socket.)
As far as I know, the supply is not TT. Whether it is TN-S, TN-C, or
TN-C-S, I have no idea.
As for why replace it, I like the idea of incorporating RCD
protection, so I'd been thinking off and on about doing it for quite
some time - the flier just crystallised some of my thoughts.
The flier has a fuzzy picture, so I may have mistaken a simple 'main
switch' for an RCBO - the only reason I know they are RCBOs is because
that's what they say in the text, rather than MCBs. My preference
would be to have individual RCBOs if I am replacing what's there, as
I run a fair amount of IT equipment/switch mode power supplies, and
I'd like to have enough headroom for leakage currents.
I've learned something about MCBs (thanks John) and overcurrent. Some
people I've spoken to have preferred fuses because (summarising their
words) "they tolerate a fair degree of overcurrent, and don't weld the
contacts together in fault currents"
Thank-you again all.
Sid
Doctor Drivel
"Sidney Endon-Lee" <unop...@mail.com> wrote in message
news:ed71e1a1-e53c-4ff0...@j24g2000yqa.googlegroups.com...
I would tend to go for double-pole RCBOs on all circuits. And, I'm this is
right, have the bathroom's light and power off just one and I know it is
easier said than done, that is why some have an RCBO on a surface patress
over the bathroom door in the hall. I think double-pole RCBOs is standard
in new installations in Germany - they use radial rather than ring circuits.
More expensive but worth it.
Sidney Endon-Lee
with like, but it seems quite amazing to have gone from fuses with a
replaceable element that (in the case of rewireable) costs a few
pennies, to dual-pole RCBOs which cost 70-80 pounds a piece!
I understand the some of the safety advantages - can't replace the
fuse with a hairgrip, RCD is good. And there's the cost of fitting
things into DIN format. It's still quite a contrast.
Sid
js.b1
> I would tend to go for double-pole RCBOs on all circuits.
Good way of ending with a mile-long CU & higher cost.
> I think double-pole RCBOs is standard
> in new installations in Germany
Standard in Italy & Germany.
Specifically because polarity is not indicated nor guaranteed.
> - they use radial rather than ring circuits.
Nothing to do with this, although several radial offer better
compliance with 314.1 than a single ring. A ring final circuit however
offers some safety benefit over radial re 2 paths to earth. A radial
final circuit of 20A offers some safety benefit over ring in that a
double 13A socket can actually only supply 19.5A yet has a 32A CPD.
Not a problem except in kitchens with few sockets and lots of heavy
appliances where Things Can Get Toasty.
> More expensive but worth it.- Hide quoted text -
Not worth it at all.
Fixed appliances have their own DP isolator, then lockoff the relevant
MCB/RCBO or main switch).
- Have an incomer Main Switch (DP Isolator).
- Have RCBO per circuit or 3x RCD (makes for a long 21-way CU which
requires a tube trip to get from one end to the other).
- Ensure at least 2 spare ways.
Also what brand are they - I ask in case one fails and you can't get
replacements re maintaining type-approval of existing board.
Contactum, Hager, MK, MEM, MG, Square-D are all a "known quantity"
whereas there is some real grotty stuff out there.
Make sure electrical tests (RCD in particular) are done on *your house/
flat* vs done on one and copied for the rest as can happen because it
can save a lot of time and a QA spark is busy looking the other way /
too busy / not checking.
I assume you have a smoke alarm?
Reason I ask is depending on the cost things might be better "spread
around".
I assume your wiring is modern PVC, not Pyro/MICC or TRS rubber?
If the latter you may get involved in a rewire of partial circuits,
one reason they might be suggesting RCBO so they can get "some
circuits back on" and fight any remedials with the remaining. Pyro is
fine, although it has some short comings (if people DIY'd in the past
they might have stuffed something enough to make an RCD trip).
Tim W
wibbled on Wednesday 11 November 2009 14:32
> Than-you for all of the very quick replies. I hope I can clear a
> couple of things up
>
> My place is one of a large development of purpose-built flats, built
> by the GLC in the 1970s. They all have Wylex rewireable fuses
Whilst a rewireable fuse isn't inherently bad *providing* no-one lashes in
the wrong size wire or a nail (which is the main criticism, along with the
lack of ease of resetting them) - but the lack of RCD protection is well
worth the effort of upgrading the CU. It's also an excellent opportunity to
assess the state of the wiring via the PIR type checks that anyone changing
a CU should be doing. 1970's wiring should be fine, but checks could still
uncover problems or even original errors like broken rings and dodgey
earths.
However, this might be something to watch out for - is the company actually
on the lookout for additional work, with the risk that they might invent
problems that can only be cured with a full rewire. Worth being ready to
challenge them on that, should it happen. Make sure they don't start any
work wihtout an agreed price and scope.
> in the
> consumer unit, which has a 60A incomer. When I moved in, there was
> still an original GLC card of fuse-wire in the cupboard with the
> consumer unit. I've not had to use any of it myself, other than for an
> electrician to add another 'way' to correct a d-i-y bodge I found in
> the kitchen (unfused spur off a socket with three sockets off the
> single ring, said spur providing power for the dishwasher, washer/
> drier, and sink waste-disposal unit, with a Fridge/freezer plugged
> into the ring socket.)
>
> As far as I know, the supply is not TT. Whether it is TN-S, TN-C, or
> TN-C-S, I have no idea.
Then there is no perceiveable reason to have a main RCD. They might be
proposing a split board with one main switch, feeding a bunch of RCBOs down
one side for sockets and then an RCD protecting a bunch of MCBs for
lighting or some variation on that scheme.
> As for why replace it, I like the idea of incorporating RCD
> protection, so I'd been thinking off and on about doing it for quite
> some time - the flier just crystallised some of my thoughts.
> The flier has a fuzzy picture, so I may have mistaken a simple 'main
> switch' for an RCBO - the only reason I know they are RCBOs is because
> that's what they say in the text, rather than MCBs. My preference
> would be to have individual RCBOs if I am replacing what's there, as
> I run a fair amount of IT equipment/switch mode power supplies, and
> I'd like to have enough headroom for leakage currents.
>
> I've learned something about MCBs (thanks John) and overcurrent. Some
> people I've spoken to have preferred fuses because (summarising their
> words) "they tolerate a fair degree of overcurrent, and don't weld the
> contacts together in fault currents"
>
> Thank-you again all.
>
> Sid
--
Tim W
wibbled on Wednesday 11 November 2009 14:56
> I would tend to go for double-pole RCBOs on all circuits. And, I'm this is
> right, have the bathroom's light and power off just one and I know it is
> easier said than done, that is why some have an RCBO on a surface patress
> over the bathroom door in the hall. I think double-pole RCBOs is standard
> in new installations in Germany - they use radial rather than ring
> circuits. More expensive but worth it.
Yes they are considerably more expensive (and harder to source), and usually
take up 2 ways rather than 1 in the CU. If they were cheaper and slimmer,
I'd agree and have done it myself. As it was, I could only justify DP on
external circuits as being a decent compromise.
Cheers
Sidney Endon-Lee
js.b1 wrote:
> ... what brand are they - I ask in case one fails and you can't get
> replacements re maintaining type-approval of existing board.
> Contactum, Hager, MK, MEM, MG, Square-D are all a "known quantity"
> whereas there is some real grotty stuff out there.
>
> Make sure electrical tests (RCD in particular) are done on *your house/
> flat* vs done on one and copied for the rest as can happen because it
> can save a lot of time and a QA spark is busy looking the other way /
> too busy / not checking.
>
> I assume you have a smoke alarm?
Yes, in fact more than one.
> Reason I ask is depending on the cost things might be better "spread
> around".
>
> I assume your wiring is modern PVC, not Pyro/MICC or TRS rubber?
All the wiring I have seen is PVC. A previous house had unshuttered BS
546 sockets with exposed conductors, rubber covered-wiring, and also
lead-sheathed paper-wrap. The fuseboxes under the stairs were a wonder
to behold. The landlord didn't care.
> If the latter you may get involved in a rewire of partial circuits,
> one reason they might be suggesting RCBO so they can get "some
> circuits back on" and fight any remedials with the remaining. Pyro is
> fine, although it has some short comings (if people DIY'd in the past
> they might have stuffed something enough to make an RCD trip).
The electrician who rectified the kitchen bodge ripped out and made
safe the other bodges we could find, including the classic use of
bellwire to carry power to a cupboard light.
Regards,
Sid
Doctor Drivel
"js.b1" <js...@ntlworld.com> wrote in message
news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
On Nov 11, 2:56 pm, "Doctor Drivel" <killef...@invalid.invalid> wrote:
> I would tend to go for double-pole RCBOs on all circuits.
Good way of ending with a mile-long CU & higher cost.
<<<
And greater protection and the lot not tripping out only that circuit.
Doctor Drivel
"js.b1" <js...@ntlworld.com> wrote in message
news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
Nothing to do with this, although several radial offer better
compliance with 314.1 than a single ring. A ring final circuit however
offers some safety benefit over radial re 2 paths to earth. A radial
final circuit of 20A offers some safety benefit over ring in that a
double 13A socket can actually only supply 19.5A yet has a 32A CPD.
Not a problem except in kitchens with few sockets and lots of heavy
appliances where Things Can Get Toasty.
<<<<<<
When using a radial circuit with an RCBO, having a 13A fuse in the plug,
rather than say a 6A using a ring, does not compromise safety, as in Germany
they do not have fuses in plugs at all with the RCBO giving all the
protection and an appliance fuse (pretty sure they have appliance fuses).
ARWadsworth
"Doctor Drivel" <kill...@invalid.invalid> wrote in message
news:hdegal$j4b$1...@news.eternal-september.org...
As long as all electrical circuits that enter a bathroom are RCD protected
then the supplementary bonding in the bathroom may be ommited. There is no
need for all the circuits to be supplied by the same RCD or RCBO though.
Adam
Doctor Drivel
"js.b1" <js...@ntlworld.com> wrote in message
news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
> I would tend to go for double-pole RCBOs on all circuits.
Good way of ending with a mile-long CU & higher cost.
> I think double-pole RCBOs is standard
> in new installations in Germany
Standard in Italy & Germany.
Specifically because polarity is not indicated nor guaranteed.
> - they use radial rather than ring circuits.
Nothing to do with this, although several radial offer better
compliance with 314.1 than a single ring. A ring final circuit however
offers some safety benefit over radial re 2 paths to earth. A radial
final circuit of 20A offers some safety benefit over ring in that a
double 13A socket can actually only supply 19.5A yet has a 32A CPD.
Not a problem except in kitchens with few sockets and lots of heavy
appliances where Things Can Get Toasty.
> More expensive but worth it.- Hide quoted text -
Not worth it at all.
Fixed appliances have their own DP isolator, then lockoff the relevant
MCB/RCBO or main switch).
<<<<<<<<<<<<<<<<<
An RCBO can be on a ring or a radial. Rings are still silly and cheap; one
of the reasons they were adopted.....and to have higher currents for
electric heaters post war as the nuclear policy was all electric, using
unmetered nuclear power. Although radials may have high currents at the
sockets too.
I recall a German looking at a British system; the RCD protecting all of the
house and the fused spurs above the worktops with a fuesd plug hidden behind
the appliance. He thought the system was mad and said it was clearly cheap
at the CU but expensive (and ugly) in fused spurs. With a socket under the
kitchen worktop with an inaccessible fuse in the plug behind a heavy
appliance that might blow. Duh!! The fused spurs looks hideous, and
expensive, as well.
Ours system is cheap and sort of nasty. In Germany to isolate a dishwasher
you go to the CU and throw the dual-pole RCBO - L & N off.
About time we went the same way as the rest of the world. On the Continent
each appliance has an RCBO at the CU. So much easier to isolate. The only
advantage of the UK system is that 3kW kettles are common, whereas in Europe
they only go to around 2kW max. But they fill their kettles with hot water
from the combi to make the heat up cheaper and faster.
Look at Continental CUs. Professional setup and on the whole quality
products. Look at the cheapo crap in Screwfix about the size of a paperback
book. On the Continent they have vertical rows of RCBOs.
AIUI in Holland proportionately to population, the number of people killed
by electrical accidents is "half" that of the UK, and they don't have rings.
Doctor Drivel
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:Z1CKm.4015$Ym4...@text.news.virginmedia.com...
That's even better. So all this bonding cable can be thrown out by buying
two RCBOs, one for the shower fan circuit, whatever one that is, and light
circuit the bathroom is off, and 15 minutes fitting at the CU. Much better.
ARWadsworth
> Sidney Endon-Lee <unop...@mail.com>
> wibbled on Wednesday 11 November 2009 14:32
>
>> Than-you for all of the very quick replies. I hope I can clear a
>> couple of things up
>>
>> My place is one of a large development of purpose-built flats, built
>> by the GLC in the 1970s. They all have Wylex rewireable fuses
>
> Whilst a rewireable fuse isn't inherently bad *providing* no-one lashes in
> the wrong size wire or a nail (which is the main criticism, along with the
> lack of ease of resetting them) - but the lack of RCD protection is well
> worth the effort of upgrading the CU. It's also an excellent opportunity
> to
> assess the state of the wiring via the PIR type checks that anyone
> changing
> a CU should be doing. 1970's wiring should be fine, but checks could still
> uncover problems or even original errors like broken rings and dodgey
> earths.
In my experience the most common problems found in 1970s installations are
There is no main or supplementary bonding, the landing lightswitch is fed
off the downstairs lighting circuit and takes it's neutral from the upstairs
circuit, high readings on the ring continuity (as you pointed out) and
unfortunately bad DIY.
Minor faults are usually no earth sleeving or red sleeving on the lighting
circuits and the odd brocken switch or socket.
The main reasons I get asked to change CUs are (in no particular order)
1. Just bought a house
2. Rewires
3. Selling a house
4. Wants to rent a house
5. The fuse box has melted etc
6. Addition works such as electric showers or extensions
> However, this might be something to watch out for - is the company
> actually
> on the lookout for additional work, with the risk that they might invent
> problems that can only be cured with a full rewire. Worth being ready to
> challenge them on that, should it happen. Make sure they don't start any
> work wihtout an agreed price and scope.
An excellent suggestion. Although there is more money in changing a CU than
there is in fixing any additional work.
Maybe an alterative quote from someone else would tell you if their standard
rate is a fair price.
Adam
ARWadsworth
"Doctor Drivel" <kill...@invalid.invalid> wrote in message
Yep. One RCBO for the electric shower, another for the bathroom lights
extractor fan/ shaver point etc and maybe a third for say an an electrical
heated towel radiator that runs off the sockets.
As long all bathroom circuits are RCD protected and the main equipotential
bonding is done then you can bin the bathroom supplementary bonding.
Adam
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> Ours system is cheap and sort of nasty. In Germany to isolate a
> dishwasher you go to the CU and throw the dual-pole RCBO - L & N off.
A safety isolator should be within easy reach of the appliance. The CU
could be several floors away.
--
*Corduroy pillows are making headlines.
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> When using a radial circuit with an RCBO, having a 13A fuse in the plug,
> rather than say a 6A using a ring, does not compromise safety, as in
> Germany they do not have fuses in plugs at all with the RCBO giving all
> the protection and an appliance fuse (pretty sure they have appliance
> fuses).
Then each and every appliance flex must be capable of tripping the RCBO of
that circuit in event of a fault.
--
*The most wasted day of all is one in which we have not laughed.*
John Rumm
To relax the requirement for supplementary bonding under the 17th
edition, they don't need to be on the same RCBO (or RCD). There are some
pre-requisites: the main EQ bonding must be in place, and the trip
threshold for the RCDs protecting the "special location" circuits must
not exceed 30mA. The RCD does not need to be local to the special
location either - in the CU is fine.
John Rumm
Its worth noting that all the new sensible price RCBOs tend to be single
pole devices. However since this is not being used for isolation and
only fault protection, there is no benefit in having double pole devices.
> is right, have the bathroom's light and power off just one and I know it
No need for it to be on the same RCD.
> is easier said than done, that is why some have an RCBO on a surface
> patress over the bathroom door in the hall. I think double-pole RCBOs
> is standard in new installations in Germany - they use radial rather
> than ring circuits. More expensive but worth it.
They need double pole RCBOs because they don't maintain the same degree
of polarity control that we do. Circumstance will dictate whether radial
or ring topology is preferable, but you can't elevate one above the
other since they both have pros and cons. Ring circuits tend to out
perform radials in the majority of common fault scenarios for example.
Radial circuits are better suited to non diverse fixed loads.
John Rumm
Single pole RCBO devices would offer the same level of fault protection
at typically a third of the cost in devices, and half the cost in CU space.
The level of discrimination between circuits does not change with the
number of poles, and so is not really relevant.
John Rumm
> An RCBO can be on a ring or a radial. Rings are still silly and cheap;
Silly no. Cheap - can depend on the circumstances, but cheap is not
necessarily a bad thing.
> one of the reasons they were adopted.....and to have higher currents for
The reasons why they were created and why they are still used are very
different. Ring circuits are far more appropriate now than they were
when conceived.
> electric heaters post war as the nuclear policy was all electric, using
> unmetered nuclear power. Although radials may have high currents at the
> sockets too.
Huh?
> I recall a German looking at a British system; the RCD protecting all of
> the house and the fused spurs above the worktops with a fuesd plug
> hidden behind the appliance. He thought the system was mad and said it
> was clearly cheap at the CU but expensive (and ugly) in fused spurs.
Appliances with concealed sockets should have separately accessible
isolation switches.
> With a socket under the kitchen worktop with an inaccessible fuse in the
> plug behind a heavy appliance that might blow. Duh!! The fused spurs
> looks hideous, and expensive, as well.
There is no need for fused spurs in most kitchens. Having said that, a
switched fused spur is not really aesthetically less pleasing than a
plain isolation switch.
Appliance fuses in general very rarely blow unless there is a fault in
the appliance, and in that case the chances are you will need to pull it
out from its utility space anyway to fix it.
> Ours system is cheap and sort of nasty. In Germany to isolate a
<snip drivel>
John Rumm
> I'll just make a small observation, which I know is not comparing like
> with like, but it seems quite amazing to have gone from fuses with a
> replaceable element that (in the case of rewireable) costs a few
> pennies, to dual-pole RCBOs which cost 70-80 pounds a piece!
Indeed. Which is why the DP devices are not used that often. The 17th
edition rules for cable protection made RCBOs more desirable (or at
least multiple RCDs[1]). The manufacturers have responded to that need
and also the one of conserving CU space by introducing far more
competitively priced single width SP RCBOs. These are still not exactly
cheap, but at under �20 in many cases are affordable. (still MCB prices
are under �2 in some cases now,
> I understand the some of the safety advantages - can't replace the
> fuse with a hairgrip, RCD is good. And there's the cost of fitting
> things into DIN format. It's still quite a contrast.
While one would be unlikely to install a rewireable fuse carrier these
days, there is nothing to stop you using cartridge fuse carriers (and
these can be handy in some circumstances).
Tim W
wibbled on Wednesday 11 November 2009 17:25
>> However, this might be something to watch out for - is the company
>> actually
>> on the lookout for additional work, with the risk that they might invent
>> problems that can only be cured with a full rewire. Worth being ready to
>> challenge them on that, should it happen. Make sure they don't start any
>> work wihtout an agreed price and scope.
>
> An excellent suggestion. Although there is more money in changing a CU
> than there is in fixing any additional work.
>
> Maybe an alterative quote from someone else would tell you if their
> standard rate is a fair price.
>
> Adam
Ideally (but slightly unfairly on the contractor as it involves potentially
lots of work for which they might not get paid if the customer backs out):
They assess the installation FOC and produce a checklist of faults on top of
the CU work and don't do anything until the additional work and price has
been agreed, as well as the price for the CU.
What you don't want as a customer is:
CU changed happily. Then they test the final circuits to fill out the EIC,
uncover a multitude of problems (real or invented) and then apply an
exhorbitent charge to fix them otherwise they cannot do the Part P
notification and you end up with a non registered and questionable
installation.
Adam might be kind enough to suggest how this sort of scenario is handled
fairly in the real world?
Cheers
ARWadsworth
A full electrical PIR on the house electrics at an agreed price before
changing the fuse box to a 17th edition CU is the fairest option. A FOC
assessment on the house electrics is only worth what you pay for it. I do
not do FOC assessments before changing a CU.
Only a madman, conman or cowboy would try to change a fuse box for a 17th
edition CU without testing the circuits before fitting the new CU.
Adam
js.b1
> CU changed happily. Then they test the final circuits to fill out the EIC,
> uncover a multitude of problems (real or invented) and then apply an
> exhorbitent charge to fix them otherwise they cannot do the Part P
> notification and you end up with a non registered and questionable
> installation.
Like you agree to pay £1800 cash for a new lighting circuit or I'm not
coming out? :-)
Before installing RCDs for the first time...
1 - Do insulation test first
2 - Check lighting for borrowed neutral/live (often very obvious)
ARWadsworth
On Nov 11, 8:22 pm, Tim W <t...@dionic.net> wrote:
> CU changed happily. Then they test the final circuits to fill out the EIC,
> uncover a multitude of problems (real or invented) and then apply an
> exhorbitent charge to fix them otherwise they cannot do the Part P
> notification and you end up with a non registered and questionable
> installation.
Like you agree to pay �1800 cash for a new lighting circuit or I'm not
coming out? :-)
I'm not "coming out" for any amount of money or any lighting circuit:-)
Before installing RCDs for the first time...
1 - Do insulation test first
2 - Check lighting for borrowed neutral/live (often very obvious)
1.Yes the insulation test is very important. Probably the most important
test.
2 If not easy then a clamp meter shows the borrowed neutrals when you are
suspicious about an existing install.
Adam
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> Rings are still silly and cheap; one
> of the reasons they were adopted.....and to have higher currents for
> electric heaters post war as the nuclear policy was all electric, using
> unmetered nuclear power.
There never was 'unmetered' power in the UK - nor was it ever likely. Just
the usual political spouting off. Nuclear power may have lowish running
costs in terms of the fuel needed - but the capital costs have always been
high. And would have to be paid for somehow.
--
*How's my driving? Call 999*
js.b1
wrote:
> I'm not "coming out" for any amount of money or any lighting circuit:-)
:-)
Re "unmetered" elec, that always amused me.
1 - Nuclear will just inflate energy company profits & taxation for HM
Treasury
2 - Any incentive for E7 making a substantial comeback must be
eliminated because it would collapse the grid infrastructure, realise
even if just the oil burning people moved to E7 the grid could not
withstand it (never mind the generating plant)
3 - Investment in plant & grid is either non-existent or hopeless,
"The City Does Not Do R&D or Maintenance" - Railways-II
4 - Gov't Investment projects are a blank cheque for the corrupt, paid
by the stupid, monitored by the incompetent, answerable to the next
government which can blame the previous government, providing
employment for innumerable quangos and art journalists too thick to
even spell science without a PR explaining it to them with coloured
bricks and 17 training courses, two marketing consultants, one
advertising consultant and finally their children until
educationalists saw that off.
UK Gov't & Oligarchy long ago decided having Lost The Empire they
would just sponge off the remaining population rather than create the
infrastructure & investment for economic leadership matched to a
portfolio of talents. I always remember one multi-million pound
business owner screaming "it is because of this technology nonsense
that we have to spend money on investment rather than ourselves", then
dumped the clutch with engine screaming in his audi quattro. Summed it
up really, when UK had an empire it appears the idea was no-one
competed - Oligarchy merely assigned it to the appropriate
individuals. Then someone decided to compete, globalisation has little
respect for the hereditary epigeneologists - and likewise the
hereditary can continue until eventually globalisation defeats
nationalism re lost social contract to be replaced of course by
religion (jews want an eye for an eye, koran not far off, christianity
makes you wait until you are dead hence preferred by Bush & Blair).
The bailout for a move to nuclear electric would be smart-meters
teleswitching CO2 heatpumps.
PeterC
You are Ian Hislop and I claim my �5!
I'd consider you to be cynical, except that the above is true and I agree
with it. Pity that it can't be repeated as widely and frequently as
GordAlmighty regurgitates his own faeces.
> The bailout for a move to nuclear electric would be smart-meters
> teleswitching CO2 heatpumps.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:Pu2dnRY7DPgXm2bX...@brightview.co.uk...
> Doctor Drivel wrote:
>
>> An RCBO can be on a ring or a radial. Rings are still silly and cheap;
>
> Silly no.
No one else adopted it except the Irish.
>> I recall a German looking at a British system; the RCD protecting all of
>> the house and the fused spurs above the worktops with a fuesd plug hidden
>> behind the appliance. He thought the system was mad and said it was
>> clearly cheap at the CU but expensive (and ugly) in fused spurs.
>
> Appliances with concealed sockets should have separately accessible
> isolation switches.
> Appliance fuses in general very rarely blow unless there is a fault in the
> appliance, and in that case the chances are you will need to pull it out
> from its utility space anyway to fix it.
Sometimes fuses just fail. The Continentals do not have fuses in their
plugs so no problem in removing a heavy appliance.
>> Ours system is cheap and sort of nasty. In Germany to isolate a
>
> <snip drivel>
You clearly have a little clue. No one else adopted our ring system.
Amazing eh!
Doctor Drivel
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:50b8bcd...@davenoise.co.uk...
> In article <hderjo$nm7$1...@news.eternal-september.org>,
> Doctor Drivel <kill...@invalid.invalid> wrote:
>> Rings are still silly and cheap; one
>> of the reasons they were adopted.....and to have higher currents for
>> electric heaters post war as the nuclear policy was all electric, using
>> unmetered nuclear power.
>
> There never was 'unmetered' power in the UK - nor was it ever likely.
They proposed and it was on public info films. See one.
<snip drivel by an effing looney>
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "js.b1" <js...@ntlworld.com> wrote in message
>> news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
>> On Nov 11, 2:56 pm, "Doctor Drivel" <killef...@invalid.invalid> wrote:
>>> I would tend to go for double-pole RCBOs on all circuits.
>>
>> Good way of ending with a mile-long CU & higher cost.
>> <<<
>>
>> And greater protection and the lot not tripping out only that circuit.
>
> Single pole RCBO devices would offer the same level of fault protection
That is total drivel.
Owain
> There never was 'unmetered' power in the UK
Not quite true - there are unmetered connections, usually for
streetlighting etc, where the cost of metering would be
disproportionate.
And that's only the legitimately unmetered connections, of course!
Owain
Tim W
wibbled on Thursday 12 November 2009 17:58
> You clearly have a little clue. No one else adopted our ring system.
> Amazing eh!
IIRC our ring system was primarily adopted as a way to turn a couple of 15A
radials into a 30A circuit with more 13A sockets on - ie an upgrade path
without the need to throw away a couple of perfectly good bits of whatever
the imperial of 2.5mm2 was. It also saved on copper.
Anyway, a system that allows loads of sockets, and upto 2 and a bit heavy
appliances and umpteen million trivial devices to be plugged in at random
locations without having to use a rediculously massive cable is a pretty
good system.
Doctor Drivel
You mean cheap. The drive towards electric heating post WW2 promoted the
ring. The advantage of the ring is that many sockets can be on the ring.
Great for offices with lots of computers. But on the Continent using
radials that is an expensive undertaking. I believe some companies adopted
the UK 3-pin sockets so they could have the fuse in the plug (essential for
a ring). The UK 3-pin plugs are the only plugs that have a fuse in them -
that I know of. They may have some on the Continent specifically for office
purposes. Then they have a cheap way of having many computers around the
office.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Indeed. Which is why the DP devices are not used that often. The 17th
> edition rules for cable protection made RCBOs more desirable (or at least
> multiple RCDs[1]). The manufacturers have responded to that need and also
> the one of conserving CU space by introducing far more competitively
> priced single width SP RCBOs. These are still not exactly cheap, but at
> under �20 in many cases are affordable. (still MCB prices are under �2 in
> some cases now,
S/fix sells the cheapest RCBO at around �28. Les than �20? Where?
ARWadsworth
"Doctor Drivel" <kill...@invalid.invalid> wrote in message
At an electrical wholesalers. I pay a lot less than �28 for RCBOs
Adam
John Rumm
I can only assume you don't understand the concept of fault protection.
The device needs to cover three fault scenarios: earth fault, over
current, and fault current. Should any of these conditions be detected,
the device needs to disconnect the line supply to the circuit.
The technology used in both SP and DP devices for all of these
activities is identical, so the detection response will be the same. The
action of either is to interrupt the the line supply to the circuit.
That the DP device interrupts the neutral also has no bearing on the
effectiveness of the detection or interruption.
There are circumstances where disconnection of the neutral is beneficial
and desirable, but these are *not* related fault protection capabilities
of the device.
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:Pu2dnRY7DPgXm2bX...@brightview.co.uk...
>> Doctor Drivel wrote:
>>
>>> An RCBO can be on a ring or a radial. Rings are still silly and cheap;
>>
>> Silly no.
>
> No one else adopted it except the Irish.
BS1362 plug and socket systems are in fairly common use around the world
- especially in countries where the UK has had a strong influence.
A common roundup would seem to include:
Sri Lanka, Bahrain, UAE, Qatar, Yemen, Oman, Cyprus, Malta, Gibraltar,
Botswana, Ghana, Hong Kong, Jordan, Macau, Brunei, Malaysia, Singapore,
Kenya, Uganda, Nigeria, Iraq, Tanzania, Zimbabwe, Belize, Dominica, St.
Lucia, St. Vincent, Grenada, and Saudi Arabia.
The requirement for a fused plug is nothing to do with the circuit
topology, but is a function of allowing a circuit to be protected at a
significantly higher current limit than the appliance. Fused plugs are
required on radial power circuits in this country for the same reason.
The lack of plug fuses in continental systems limits the maximum circuit
current carrying capacity dramatically. This requires a proliferation
of circuits to meet modern usage patterns, resulting in more cost and
complexity with no gain is performance or safety (in fact with a
reduction in safety).
John Rumm
And would you care to tell us where unmetered power was actually provided?
Steve Firth
> They
>
> <snip drivel by an effing looney>
I followed the instruction.
js.b1
> Not quite true - there are unmetered connections, usually for
> streetlighting etc, where the cost of metering would be
> disproportionate. And that's only the legitimately
> unmetered connections, of course!
Indeed :-)
Quite a few street lights round here had their cables running off in
the direction of the nearby house, I presume to their cutout. That
would explain the "dig for electricity" in some areas - until the
metering people checked upstream meters!
I recall there was a "flat fee" system for lighting at one point, with
heating sockets being charged for. You could almost say E7 was
"unmetered" - I recall 2p/minute evening for 300bps telephone
(Micronet) and 1.6p/unit for E7 overnight kWhr.
js.b1
TLC do them for about £23 off the top of my head.
Comes down to the brand, quantity & person and which wholesaler.
14 RCBO can be had for £250 which is not that bad - consider how much
14 MCB and 3 100A RCD cost :-)
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:jPSdnfHC67xqn2bX...@brightview.co.uk...
>>> Doctor Drivel wrote:
>>>>
>>>> "js.b1" <js...@ntlworld.com> wrote in message
>>>> news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
>>>> On Nov 11, 2:56 pm, "Doctor Drivel" <killef...@invalid.invalid> wrote:
>>>>> I would tend to go for double-pole RCBOs on all circuits.
>>>>
>>>> Good way of ending with a mile-long CU & higher cost.
>>>> <<<
>>>>
>>>> And greater protection and the lot not tripping out only that circuit.
>>>
>>> Single pole RCBO devices would offer the same level of fault protection
>>
>> That is total drivel.
>
> I can only assume
Some device that isolates the L & N when it activates must offer a higher
level of safety.
js.b1
> Some device that isolates the L & N when it activates must offer a higher
For TT - yes.
For TN-C-S - no, not at all.
With PME both N&E are joined at the cutout, so you just disconnect N
yet E is still connected - so no logic there. You must not isolate E
under BS7671 reg blah-blah-blah (can't recall the damn number). Three
pole isolators are for L1 L2 N not LNE (contrary to some numpties I've
met).
Dave Plowman (News)
<f34e5efc-238a-409e...@v25g2000yqk.googlegroups.com>,
Owain <spuorg...@gowanhill.com> wrote:
> On 11 Nov, 22:34, "Dave Plowman (News)" wrote:
> > There never was 'unmetered' power in the UK
> Not quite true - there are unmetered connections, usually for
> streetlighting etc, where the cost of metering would be
> disproportionate.
Don't you start with the red herrings. ;-)
> And that's only the legitimately unmetered connections, of course!
> Owain
--
*I brake for no apparent reason.
Dave Plowman (News)
Tim W <t...@dionic.net> wrote:
> > You clearly have a little clue. No one else adopted our ring system.
> > Amazing eh!
> IIRC our ring system was primarily adopted as a way to turn a couple of
> 15A radials into a 30A circuit with more 13A sockets on - ie an upgrade
> path without the need to throw away a couple of perfectly good bits of
> whatever the imperial of 2.5mm2 was. It also saved on copper.
> Anyway, a system that allows loads of sockets, and upto 2 and a bit
> heavy appliances and umpteen million trivial devices to be plugged in at
> random locations without having to use a rediculously massive cable is a
> pretty good system.
It's the envy of many. A pal visiting from the US couldn't believe just
how flexible it was - he'd been told we still used lots of different plug
sizes. And was most impressed with how quick you could boil water in an
electric kettle.
But all this thread shows is dribble knows even less about house wiring
than heating...
--
*Why doesn't glue stick to the inside of the bottle?
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> "Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
> news:50b8bcd...@davenoise.co.uk...
> > In article <hderjo$nm7$1...@news.eternal-september.org>,
> > Doctor Drivel <kill...@invalid.invalid> wrote:
> >> Rings are still silly and cheap; one of the reasons they were
> >> adopted.....and to have higher currents for electric heaters post war
> >> as the nuclear policy was all electric, using unmetered nuclear power.
> >
> > There never was 'unmetered' power in the UK - nor was it ever likely.
> They proposed and it was on public info films. See one.
'They' propose lots of things there are votes in. Haven't you learned
anything?
> <snip drivel by an effing looney>
So you think nuclear power stations costs nothing to build too?
Time you went back into treatment. Although that expensive German clinic
doesn't seem to have helped.
--
*I don't suffer from insanity -- I'm a carrier
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
>> news:50b8bcd...@davenoise.co.uk...
>>> In article <hderjo$nm7$1...@news.eternal-september.org>,
>>> Doctor Drivel <kill...@invalid.invalid> wrote:
>>>> Rings are still silly and cheap; one
>>>> of the reasons they were adopted.....and to have higher currents for
>>>> electric heaters post war as the nuclear policy was all electric, using
>>>> unmetered nuclear power.
>>>
>>> There never was 'unmetered' power in the UK - nor was it ever likely.
>>
>> They proposed and it was on public info films. See one.
>
> And would you care to tell us where unmetered power was actually provided?
The key word was "proposed". The nation was to be all electric, hence
electrical supplies to homes capable of heating the home electrically. The
dirty Gas industry, making gas from dirty coal with ugly gas works in urban
areas was to be scaled down. The downturn in nuclear because of accidents
and the discovery of North Sea Gas changed the strategy.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:Pu2dnRY7DPgXm2bX...@brightview.co.uk...
>>> Doctor Drivel wrote:
>>>
>>>> An RCBO can be on a ring or a radial. Rings are still silly and cheap;
>>>
>>> Silly no.
>>
>> No one else adopted it except the Irish.
>
> BS1362 plug and socket systems are in fairly common use around the world -
> especially in countries where the UK has had a strong influence.
>
> A common roundup would seem to include:
>
> Sri Lanka, Bahrain, UAE, Qatar, Yemen, Oman, Cyprus, Malta, Gibraltar,
> Botswana, Ghana, Hong Kong, Jordan, Macau, Brunei, Malaysia, Singapore,
> Kenya, Uganda, Nigeria, Iraq, Tanzania, Zimbabwe, Belize, Dominica, St.
> Lucia, St. Vincent, Grenada, and Saudi Arabia.
Saudi Arabia? They have anything that goes.I have seen many types there.
No EU country want to know it except Ireland, who are tied to the apron
strings of the UK.
> The requirement for a fused plug is nothing to do with the circuit
> topology,
For a ring to safely work it needs the correct fuse in the plug.
> but is a function of allowing a circuit to be protected at a significantly
> higher current limit than the appliance.
An appliance fuse can offer the correct protection. I have seen appliance
fuses in France, whereas in the UK they would not be there. Ina ring with
32A mcb at the CU, needs the fuse in the plug for correct protection. Many
appliances that need 6A fuses have 13A in the plug. The system is open to
abuse. The fuse is primarily to protect the appliance cable.
> Fused plugs are required on radial power circuits in this country for the
> same reason.
> The lack of plug fuses in continental systems limits the maximum circuit
> current carrying capacity dramatically.
Which is a good thing as it gives more protection as an appliance on a ring
can be hopelessly out of protection range if such a simple thing like a 13A
fuse is installed, when say a 3A is needed.
> This requires a proliferation of circuits to meet modern usage patterns,
> resulting in more cost and complexity with no gain is performance or
> safety (in fact with a reduction in safety).
Mr drivel detectoris on and identified some. A properly installed radial
system offers greater protection, especially with DP RCBOs.
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> Some device that isolates the L & N when it activates must offer a
> higher level of safety.
Why not go the whole hog and isolate the earth too? Makes as much sense.
--
*Oh, what a tangled website we weave when first we practice *
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> You mean cheap. The drive towards electric heating post WW2 promoted
> the ring. The advantage of the ring is that many sockets can be on the
> ring. Great for offices with lots of computers.
That's one of the situations where you should dedicated radials, actually.
Please stick to what you know about. Which will make your posts brief in
the extreme.
--
*Even a blind pig stumbles across an acorn now and again *
Doctor Drivel
Even price-wise RCBOs appears the way to go.
Doctor Drivel
"Steve Firth" <%steve%@malloc.co.uk> wrote in message
news:1j934gt.n3wqyb17g55ohN%%steve%@malloc.co.uk...
> Doctor Drivel <kill...@invalid.invalid> wrote:
>
>> They
>>
>> <snip drivel by an effing looney>
>
> I followed
This one need effing tagging. One weirdo!
Doctor Drivel
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:ggZKm.4369$Ym4...@text.news.virginmedia.com...
I use S/fix as a guide as they were highly competitive. Not so now.
The Natural Philosopher
>
> Why not go the whole hog and isolate the earth too? Makes as much sense.
>
That's what Space is for.
Tim W
wibbled on Thursday 12 November 2009 21:59
> For a ring to safely work it needs the correct fuse in the plug.
That would be equally true of a radial that wasn't dedicated, and the
overcurrent protection set accordingly, to a single appliance or class of
appliance. In the most extreme case, a 32A radial is a "standard circuit",
though rare due to being not so practical to implement.
Doctor Drivel
> In article <hdhvc6$40t$1...@news.eternal-september.org>,
> Doctor Drivel <kill...@invalid.invalid> wrote:
>> Some device that isolates the L & N when it activates must offer a
>> higher level of safety.
>
> Why not go the whole hog and isolate the earth too? Makes as much sense.
Oh my God! He must eff off for his own good.
Rod
<>
> There never was 'unmetered' power in the UK - nor was it ever likely.
<>
>
But it is interesting to consider the impact that unmetered electricity
might have. Just how much electricity would we use if it were unmetered?
I can imagine having a lovely warm greenhouse with grow lights to
provide fresh fruit, vegetables and herbs all year round. (Carefully
avoiding light spill, of course.)
But I suppose eventually we'd end up using so much that there would be
literal global warming.
--
Rod
Doctor Drivel
> In article <hdhme0$kjb$1...@news.eternal-september.org>,
> Doctor Drivel <kill...@invalid.invalid> wrote:
>> You mean cheap. The drive towards electric heating post WW2 promoted
>> the ring. The advantage of the ring is that many sockets can be on the
>> ring. Great for offices with lots of computers.
>
> That's
Please eff off as you are a plantpot.
Doctor Drivel
> In article <hdhlh2$d7k$1...@news.eternal-september.org>,
> Tim W <t...@dionic.net> wrote:
>> > You clearly have a little clue. No one else adopted our ring system.
>> > Amazing eh!
>
>> IIRC our ring system was primarily adopted as a way to turn a couple of
>> 15A radials into a 30A circuit with more 13A sockets on - ie an upgrade
>> path without the need to throw away a couple of perfectly good bits of
>> whatever the imperial of 2.5mm2 was. It also saved on copper.
>
>> Anyway, a system that allows loads of sockets, and upto 2 and a bit
>> heavy appliances and umpteen million trivial devices to be plugged in at
>> random locations without having to use a rediculously massive cable is a
>> pretty good system.
>
> It's
You must eff off as you are a plantpot.
Doctor Drivel
"Tim W" <t...@dionic.net> wrote in message
news:hdi23f$n2i$1...@news.eternal-september.org...
> Doctor Drivel <kill...@invalid.invalid>
> wibbled on Thursday 12 November 2009 21:59
>
>
>> For a ring to safely work it needs the correct fuse in the plug.
>
> That would be equally true of a radial that wasn't dedicated, and the
> overcurrent protection set accordingly, to a single appliance or class of
> appliance. In the most extreme case, a 32A radial is a "standard circuit",
> though rare due to being not so practical to implement.
A radial with only 8 sockets on it, maximum, and rated to 16A is safer when
abused. Some appliances can be only protected by a 32A mcb.
Doctor Drivel
> In article <hdhip5$mg9$2...@news.eternal-september.org>,
> Doctor Drivel <kill...@invalid.invalid> wrote:
>
>> "Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
>> news:50b8bcd...@davenoise.co.uk...
>> > In article <hderjo$nm7$1...@news.eternal-september.org>,
>> > Doctor Drivel <kill...@invalid.invalid> wrote:
>> >> Rings are still silly and cheap; one of the reasons they were
>> >> adopted.....and to have higher currents for electric heaters post war
>> >> as the nuclear policy was all electric, using unmetered nuclear power.
>> >
>> > There never was 'unmetered' power in the UK - nor was it ever likely.
>
>> They proposed and it was on public info films. See one.
>
> 'They'
Please eff off you are a plantpot.
Doctor Drivel
"Rod" <poly...@ntlworld.com> wrote in message
news:7m3gigF...@mid.individual.net...
Not if we implement tidal lagoons in the Irish Sea and have very high
insulation levels in homes to reduce heating demand then we can use it
unmetered. Of course car will electric as will all trains. Then cars must
be restricted from town and city centres.
Dave Plowman (News)
Doctor Drivel <kill...@invalid.invalid> wrote:
> > The requirement for a fused plug is nothing to do with the circuit
> > topology,
> For a ring to safely work it needs the correct fuse in the plug.
Please explain. Do you think a lighting outlet which is only fused at the
CU somehow 'safer' than a 13 amp socket?
Please demonstrate this with your finger...
--
*I didn't drive my husband crazy -- I flew him there -- it was faster
Frank Erskine
wrote:
>Dave Plowman (News) wrote:
><>
>> There never was 'unmetered' power in the UK - nor was it ever likely.
><>
>>
>
>But it is interesting to consider the impact that unmetered electricity
>might have. Just how much electricity would we use if it were unmetered?
>I can imagine having a lovely warm greenhouse with grow lights to
>provide fresh fruit, vegetables and herbs all year round. (Carefully
>avoiding light spill, of course.)
Streetlighting supplies aren't normally metered, nor are supplies to,
for example, cable TV cabinets.
There's just an agreed payment to the leccy supplier.
--
Frank Erskine
The Natural Philosopher
we don't breathe all the air do we? and that's free.
Steve Firth
> Saudi Arabia? They have anything that goes.I have seen many types there.
> No EU country want to know it except Ireland, who are tied to the apron
> strings of the UK.
More bullshit from Drivel. Malta, an EU country uses BS1363, as does the
Republic of Cyprus.
You must enjoy being wrong all the time, eh Drivel.
Rod
<>
>
> we don't breathe all the air do we? and that's free.
But we have finite lung capacity and a maximum rate at which we can
breathe. With unmetered, you could always add a few kW of usage quite
easily... Like at work where one person puts on a fan heater while the
a/c is working flat out to keep it cool.
--
Rod
Steve Firth
> we don't breathe all the air do we?
... yet.
Unless we stop procreating like bacteria in Drivel's kitchen then we
will soon breathe all the air.
Dave Plowman (News)
Frank Erskine <frank....@btinternet.com> wrote:
> >But it is interesting to consider the impact that unmetered electricity
> > might have. Just how much electricity would we use if it were
> >unmetered? I can imagine having a lovely warm greenhouse with grow
> >lights to provide fresh fruit, vegetables and herbs all year round.
> >(Carefully avoiding light spill, of course.)
> Streetlighting supplies aren't normally metered, nor are supplies to,
> for example, cable TV cabinets.
> There's just an agreed payment to the leccy supplier.
But both those items use a predefined amount of electricity. A house is
rather different. Nor could you judge the requirement on present
consumption - if it were 'free' many would use it wastefully.
--
*How many roads must a man travel down before he admits he is lost? *
Doctor Drivel
> In article <hdi14i$i9n$1...@news.eternal-september.org>,
> Doctor Drivel <kill...@invalid.invalid> wrote:
>> > The requirement for a fused plug is nothing to do with the circuit
>> > topology,
>
>> For a ring to safely work it needs the correct fuse in the plug.
>
> Please explain.
Please eff off as you are a plantpot
Doctor Drivel
> Doctor Drivel <kill...@invalid.invalid> wrote:
>
>> Saudi Arabia? They have anything that goes.I have seen many types there.
>> No EU country want to know it except Ireland, who are tied to the apron
>> strings of the UK.
>
> More
This pervo needs tagging. He is a Gary Glitter fan.
Doctor Drivel
This pervo needs tagging.
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> Doctor Drivel wrote:
>>>
>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>>>>
>>>>> On Nov 11, 2:56 pm, "Doctor Drivel" <killef...@invalid.invalid> wrote:
>>>>>> I would tend to go for double-pole RCBOs on all circuits.
>>>>>
>>>>> Good way of ending with a mile-long CU & higher cost.
>>>>> <<<
>>>>>
>>>>> And greater protection and the lot not tripping out only that circuit.
>>>>
>>>> Single pole RCBO devices would offer the same level of fault protection
>>>
>>> That is total drivel.
>>
>> I can only assume
>
> Some device that isolates the L & N when it activates must offer a
> higher level of safety.
No, this is an area where you can't generalise without knowing the
specifics. Firstly you are confusing fault protection with some nebulous
concept of "safety". Fault protection has a specific meaning and there
are specific requirements. SP and DP devices both fulfil these
requirements.
To extend the discussion to safety in general, then you need to look at
a wider picture, like can the neutral take on a noticeably different
potential to the local earth? For many cases (i.e. TN-C-S / TN-S) the
difference between DP and SP is moot, and even with TT it is negligible.
The time that DP device does have a clear advantage is that you can also
use it for isolation (something that requires DP switching).
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>>> In article <hderjo$nm7$1...@news.eternal-september.org>,
>>>> Doctor Drivel <kill...@invalid.invalid> wrote:
>>>>> Rings are still silly and cheap; one
>>>>> of the reasons they were adopted.....and to have higher currents for
>>>>> electric heaters post war as the nuclear policy was all electric,
>>>>> using
>>>>> unmetered nuclear power.
>>>>
>>>
>>
>> provided?
>
> The key word was "proposed".
Ah, so you mean you were actually agreeing with Dave when he said "There
never was 'unmetered' power in the UK"
--
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>
>> Indeed. Which is why the DP devices are not used that often. The 17th
>> edition rules for cable protection made RCBOs more desirable (or at
>> least multiple RCDs[1]). The manufacturers have responded to that need
>> and also the one of conserving CU space by introducing far more
>> competitively priced single width SP RCBOs. These are still not
>> exactly cheap, but at under �20 in many cases are affordable. (still
>> MCB prices are under �2 in some cases now,
>
> S/fix sells the cheapest RCBO at around �28. Les than �20? Where?
One example:
http://cpc.farnell.com/pro-elec/aub1r-10a/rcbo-single-pole-10a/dp/PL10655
(not a recommendation, since I have never used the brand)
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> Doctor Drivel wrote:
>>>
>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>>> Doctor Drivel wrote:
>>>>
>>>>> An RCBO can be on a ring or a radial. Rings are still silly and
>>>>> cheap;
>>>>
>>>> Silly no.
>>>
>>> No one else adopted it except the Irish.
>>
>> BS1362 plug and socket systems are in fairly common use around the
>> world - especially in countries where the UK has had a strong influence.
>>
>> A common roundup would seem to include:
>>
>> Sri Lanka, Bahrain, UAE, Qatar, Yemen, Oman, Cyprus, Malta, Gibraltar,
>> Botswana, Ghana, Hong Kong, Jordan, Macau, Brunei, Malaysia,
>> Singapore, Kenya, Uganda, Nigeria, Iraq, Tanzania, Zimbabwe, Belize,
>> Dominica, St. Lucia, St. Vincent, Grenada, and Saudi Arabia.
>
> Saudi Arabia? They have anything that goes.I have seen many types
Indeed they do, BS1363 among them.
>> The requirement for a fused plug is nothing to do with the circuit
>> topology,
>
> For a ring to safely work it needs the correct fuse in the plug.
This has nothing to do with it being a ring, and everything to do with
it being a 32A circuit.
>> but is a function of allowing a circuit to be protected at a
>> significantly higher current limit than the appliance.
>
> An appliance fuse can offer the correct protection. I have seen
How does the appliance fuse protect the appliance flex?
> appliance fuses in France, whereas in the UK they would not be there.
Appliance fuses, where used are pretty much universal across the euro
zone. Appliance fuses also offer less protection outside the UK, since
you can only assume they are in the live wire 50% of the time.
> Ina ring with 32A mcb at the CU, needs the fuse in the plug for correct
> protection. Many appliances that need 6A fuses have 13A in the plug.
> The system is open to abuse. The fuse is primarily to protect the
> appliance cable.
Indeed. Many modern appliance flexes will also be sized (and restricted
in length) to ensure that they have adequate fault protection from a 13A
fuse (and 16A circuit breaker) - even if the overload protection
required by the appliance is lower.
One area where this is less desirable however is with small portable
appliances, where there is benefit to being able to use smaller lighter
flex than would otherwise be required.
The scope for abuse these days is greatly reduced since appliance plugs
come pre fitted and fused, and fuses rarely need replacement.
>> Fused plugs are required on radial power circuits in this country for
>> the same reason.
>
>
>> The lack of plug fuses in continental systems limits the maximum
>> circuit current carrying capacity dramatically.
>
> Which is a good thing as it gives more protection as an appliance on a
> ring can be hopelessly out of protection range if such a simple thing
> like a 13A fuse is installed, when say a 3A is needed.
The appliance is protected by its own fuse. You will be relatively hard
pushed to many devices fitted with 3A flex that are capable of
overloading the flex.
>
>> This requires a proliferation of circuits to meet modern usage
>> patterns, resulting in more cost and complexity with no gain is
>> performance or safety (in fact with a reduction in safety).
>
> Mr drivel detectoris on and identified some. A properly installed
> radial system offers greater protection, especially with DP RCBOs.
So a radial with a disconnected or high resistance earth connection
somewhere along its length is better than a ring with the same fault?
Tim W
wibbled on Thursday 12 November 2009 22:37
Even when the appliances all have 0.5mm2 flexes?
Do you strip your wires with a hacksaw too? Go back to plumbing, at least
you'll only get wet...
The Natural Philosopher
Which puts a neat upper limit on our power consumption doesn't it?
Steve Firth
As another poster sig mentions, Malthus was right. Predicting when the
inevitable collapse will happen is more difficult. Governments have
already shown they can't even take difficult decisions over energy
supply. Taking much more difficult positions over nitwits who think a
religion allows them to breed like bugs is never going to happen.
Owain
> A radial with only 8 sockets on it, maximum, and rated to 16A is safer when
> abused.
But absolutely useless for practical purposes. We'd end up like the
Americans, having to work out which combinations of sockets and
appliances don't trip anything.
I didn't think ring abuse was that widespread so as to be a problem.
Owain
Owain
> Doctor Drivel wrote:
> > For a ring to safely work it needs the correct fuse in the plug.
> Please explain. Do you think a lighting outlet which is only fused at the
> CU somehow 'safer' than a 13 amp socket?
Lighting circuits are safer where Drivel lives - they're all tamper-
resistant ligature-free recessed fittings
Owain
Tim W
wibbled on Friday 13 November 2009 10:11
I'm doing that at the moment, running my entire house (bar water heater) off
1 32A temp ring and a rather unhealthy assortment of extension leads.
SWMBO's been "instructed" as to which fan heater to turn off to run, say the
washing machine...
It's quite a weird existence (and a right PITA if I didn't know it would be
ending soon), but it's amazing how much stuff you can run with a single
maxed out 32A circuit. Not for long. Next week, I should have 3 final rings
done properly...
It's almost amazing the nice meals you can conjure up with one combi
microwave, a rice cooker (apart from the bloody thing drips condensate on
its own IEC plug and trips the RCBO(!) and a slow cooker. Wondering whether
to bother getting a real cooker ;-O
In case anyone says "wire your rings, lazy git", today's task was clearing
all the gutters (I like bungalows in this respect) - got fed up with the
waterfalls everywhere :)
Next task is have a bath. The get son from nursery, set up tonight's meal in
the slow cooker and clear up a bit so I can get round to do the wiring next
week.
Cheers
Tim
Doctor Drivel
> Doctor Drivel <kill...@invalid.invalid>
> wibbled on Thursday 12 November 2009 22:37
>
>>
>> "Tim W" <t...@dionic.net> wrote in message
>> news:hdi23f$n2i$1...@news.eternal-september.org...
>>> Doctor Drivel <kill...@invalid.invalid>
>>> wibbled on Thursday 12 November 2009 21:59
>>>
>>>
>>>> For a ring to safely work it needs the correct fuse in the plug.
>>>
>>> That would be equally true of a radial that wasn't dedicated, and the
>>> overcurrent protection set accordingly, to a single appliance or class
>>> of
>>> appliance. In the most extreme case, a 32A radial is a "standard
>>> circuit", though rare due to being not so practical to implement.
>>
>> A radial with only 8 sockets on it, maximum, and rated to 16A is safer
>> when abused. Some appliances can be only protected by a 32A mcb
>
> Even when the appliances all have 0.5mm2 flexes?
>
> Do you strip your wires with a hacksaw too? Go back to plumbing, at least
> you'll only get wet...
You lack common sense. I woudl let you near my house. There again I do all
my own.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:n-6dnc_o14EV_2HX...@brightview.co.uk...
>>> Doctor Drivel wrote:
>>>>
>>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>>> news:jPSdnfHC67xqn2bX...@brightview.co.uk...
>>>>> Doctor Drivel wrote:
>>>>>>
>>>>>> "js.b1" <js...@ntlworld.com> wrote in message
>>>>>> news:f6eb5350-a7ff-477e...@s31g2000yqs.googlegroups.com...
>>>>>> On Nov 11, 2:56 pm, "Doctor Drivel" <killef...@invalid.invalid>
>>>>>> wrote:
>>>>>>> I would tend to go for double-pole RCBOs on all circuits.
>>>>>>
>>>>>> Good way of ending with a mile-long CU & higher cost.
>>>>>> <<<
>>>>>>
>>>>>> And greater protection and the lot not tripping out only that
>>>>>> circuit.
>>>>>
>>>>> Single pole RCBO devices would offer the same level of fault
>>>>> protection
>>>>
>>>> That is total drivel.
>>>
>>> I can only assume
>>
>> Some device that isolates the L & N when it activates must offer a higher
>> level of safety.
>
> No, this is an area where you can't generalise without knowing the
> specifics. Firstly you are confusing fault protection with some nebulous
> concept of "safety".
I am not. If the device activates and cuts out all electricity conductors
(L&N) it must by definition be safer. In fact if the earth is isolated even
better, then all electrical conductors are isolated from the appliance or
circuit.
> The time that DP device does have a clear advantage is that you can also
> use it for isolation (something that requires DP switching).
yep.
Doctor Drivel
"Owain" <spuorg...@gowanhill.com> wrote in message
news:e80c9d6f-29f4-4c6c...@b15g2000yqd.googlegroups.com...
> On 12 Nov, 22:37, "Doctor Drivel" wrote:
>> A radial with only 8 sockets on it, maximum, and rated to 16A is safer
>> when
>> abused.
>
> But absolutely useless for practical purposes. We'd end up like the
> Americans, having to work out which combinations of sockets and
> appliances don't trip anything.
When a wire becomes loose in a ring it is difficult to trace. As it is fed
from two ends. It could mean one section of cable in the ring is cooking as
the other section is isolated because of a wire coming loose.
If daisy chained sockets on a radial, and one has loose wire those
downstream will not operate. On a ring all appears fine until a high current
appliance is connected.
> I didn't think ring abuse was that widespread so as to be a problem.
Ring abuse is widespread. I have noticed square 3-pin plugs with no fuses
being sold (prob illegally). That means the appliance, which could be a
table lamp, is only protected by a 32A fuse or mcb.
ARWadsworth
"Doctor Drivel" <kill...@invalid.invalid> wrote in message
news:hdjln1$62h$3...@news.eternal-september.org...
No.
Only the live and neutral are the electrical (phase) conductors. The earth
is a circuit protective conductor. The earth connection does it's job
properly by not having it's circuit broken.
You would not want for example a lump of metal such as a combi boiler and
it's copper pipework to have all it's live, neutral and earth connections
isolated when you turn the power off to it.
That would mean that a fault elsewhere, such as a live cable from another
circuit touching a copper pipe would make the combi and it's pipework rise
up to 230V.
Adam
ARWadsworth
"Doctor Drivel" <kill...@invalid.invalid> wrote in message
>
> "Owain" <spuorg...@gowanhill.com> wrote in message
> news:e80c9d6f-29f4-4c6c...@b15g2000yqd.googlegroups.com...
>> On 12 Nov, 22:37, "Doctor Drivel" wrote:
>>> A radial with only 8 sockets on it, maximum, and rated to 16A is safer
>>> when
>>> abused.
>>
>> But absolutely useless for practical purposes. We'd end up like the
>> Americans, having to work out which combinations of sockets and
>> appliances don't trip anything.
>
> When a wire becomes loose in a ring it is difficult to trace. As it is fed
> from two ends. It could mean one section of cable in the ring is cooking
> as the other section is isolated because of a wire coming loose.
It is not that difficult to trace if you have the experience and equipment.
> If daisy chained sockets on a radial, and one has loose wire those
> downstream will not operate. On a ring all appears fine until a high
> current appliance is connected.
What happens if it is the earth terminal that is loose?
>> I didn't think ring abuse was that widespread so as to be a problem.
>
> Ring abuse is widespread.
It is in the Catholic church.
Adam
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:0YednQX_veda-mHX...@brightview.co.uk...
>>> Doctor Drivel wrote:
>>>>
>>>> "Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
>>>> news:50b8bcd...@davenoise.co.uk...
>>>>> In article <hderjo$nm7$1...@news.eternal-september.org>,
>>>>> Doctor Drivel <kill...@invalid.invalid> wrote:
>>>>>> Rings are still silly and cheap; one
>>>>>> of the reasons they were adopted.....and to have higher currents for
>>>>>> electric heaters post war as the nuclear policy was all electric,
>>>>>> using
>>>>>> unmetered nuclear power.
>>>>>
>>>>> There never was 'unmetered' power in the UK - nor was it ever likely.
>>>>
>>>> They proposed and it was on public info films. See one.
>>>
>>> And would you care to tell us where unmetered power was actually
>>> provided?
>>
>> The key word was "proposed".
>
> Ah, so you mean you were actually agreeing
I not agree with loonies and plantpots.
Doctor Drivel
> Taking much more difficult positions over nitwits who think a
> religion allows them to breed like bugs is never going to happen.
This one need tagging. What a pervo!
Doctor Drivel
> Owain <spuorg...@gowanhill.com>
> wibbled on Friday 13 November 2009 10:11
>
>> On 12 Nov, 22:37, "Doctor Drivel" wrote:
>>> A radial with only 8 sockets on it, maximum, and rated to 16A is safer
>>> when abused.
>>
>> But absolutely useless for practical purposes. We'd end up like the
>> Americans, having to work out which combinations of sockets and
>> appliances don't trip anything.
>>
>> I didn't think ring abuse was that widespread so as to be a problem.
>>
>> Owain
>
> I'm doing that at the moment, running my entire house (bar water heater)
> off
> 1 32A temp ring and a rather unhealthy assortment of extension leads.
>
> SWMBO's been "instructed" as to which fan heater to turn off to run, say
> the
> washing machine...
And this is lecturing people on electricity. Amazing. The man is a walking
fire hazard.
Doctor Drivel
Great for kids.
Doctor Drivel
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:R9dLm.4604$Ym4...@text.news.virginmedia.com...
I know what the earth is for. If in a safety situation a device trips and
E,N & L are isolate it is the ultimate safety. Why because the earth could
be live from a fault elsewhere. isolating all three is the ultimate..
> You would not want for example a lump of metal such as a combi boiler and
> it's copper pipework to have all it's live, neutral and earth connections
> isolated when you turn the power off to it.
Why not? If all three are isolated there is no problem.
> That would mean that a fault elsewhere, such as a live cable from another
> circuit touching a copper pipe would make the combi and it's pipework rise
> up to 230V.
Being to earth, via pipes, the combi protects itself.