cooker hood off 32A 4mm radial "spur"
sm_jamieson
off the 32A 4mm radial for fixed appliances. Is it OK to create a spur
using an inaccessible-type junction box (not plastered in, just behind
some units) rather than at a socket ? Can't think why not, but y'know
best to check.
Any limit to the length of "spur" ?
Simon.
sm_jamieson
Sorry, forgot to say, the wiring at that point is behind units, but
all surface wired.
The wiring will go from surface wired to buried in a horizontal line
with an FSU that will be just above the wall units, so not visible
from most positions.
Simon.
John Rumm
Yup, sounds ok. Spur can be in 2.5mm^2 T&E, and you probably need the
SFCU fused at 3A - but follow the cooker hood instructions on that.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
ARWadsworth
> On 12/04/2011 18:50, sm_jamieson wrote:
>> On Apr 12, 6:39 pm, sm_jamieson<sm_jamie...@hotmail.com> wrote:
>>> I've decided the best way to connect my cooker hood is via a "spur"
>>> off the 32A 4mm radial for fixed appliances. Is it OK to create a
>>> spur using an inaccessible-type junction box (not plastered in,
>>> just behind some units) rather than at a socket ? Can't think why
>>> not, but y'know best to check.
>>> Any limit to the length of "spur" ?
>>> Simon.
>>
>> Sorry, forgot to say, the wiring at that point is behind units, but
>> all surface wired.
>> The wiring will go from surface wired to buried in a horizontal line
>> with an FSU that will be just above the wall units, so not visible
>> from most positions.
>> Simon.
>
> Yup, sounds ok. Spur can be in 2.5mm^2 T&E, and you probably need the
> SFCU fused at 3A - but follow the cooker hood instructions on that.
Well that advice (although sound) is just the sort of thing that will give
Dennis a heart attack.
I would not actually be happy with a junction box behind kitchen units if it
is only a few feet to the nearest socket.
--
Adam
John Rumm
> John Rumm<see.my.s...@nowhere.null> wrote:
>> On 12/04/2011 18:50, sm_jamieson wrote:
>>> On Apr 12, 6:39 pm, sm_jamieson<sm_jamie...@hotmail.com> wrote:
>>>> I've decided the best way to connect my cooker hood is via a "spur"
>>>> off the 32A 4mm radial for fixed appliances. Is it OK to create a
>>>> spur using an inaccessible-type junction box (not plastered in,
>>>> just behind some units) rather than at a socket ? Can't think why
>>>> not, but y'know best to check.
>>>> Any limit to the length of "spur" ?
>>>> Simon.
>>>
>>> Sorry, forgot to say, the wiring at that point is behind units, but
>>> all surface wired.
>>> The wiring will go from surface wired to buried in a horizontal line
>>> with an FSU that will be just above the wall units, so not visible
>>> from most positions.
>>> Simon.
>>
>> Yup, sounds ok. Spur can be in 2.5mm^2 T&E, and you probably need the
>> SFCU fused at 3A - but follow the cooker hood instructions on that.
>
> Well that advice (although sound) is just the sort of thing that will give
> Dennis a heart attack.
I have misplaced my "clue by four", so I can't give him a smack with it...
> I would not actually be happy with a junction box behind kitchen units if it
> is only a few feet to the nearest socket.
Indeed - at a socket (FCU etc) would be best (assuming its a socket
circuit!)
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:z66dnaCOspuVJTnQ...@brightview.co.uk...
Why would it be better, you both claimed that the spurs are perfectly safe.
ARWadsworth
Do you ever read what you have written before pressing the send button?
--
Adam
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io2ioe$drp$1...@dont-email.me...
> Do you ever read what you have written before pressing the send button?
Too thick to understand what I say are you?
John Rumm
Non sequitur...
<rummage> Ah, found it!
Come 'ere you dozy twonk...
<fx whoosh, whack, Owwww>
It would be better to originate your spur from an existing accessory
that is to remain visible such as a socket or a FCU etc, rather than
originate it from a concealed junction box. This is assuming the JB is a
screw connection type that should remain available for inspection. If
using a maintenance free JB then that is a different matter. The issue
at hand is whether the junction box remains accessible, and has
absolutely nothing to do with spurs.
The spur would obviously be perfectly safe (yes even to you denis),
since it would not be feasible to overload a 2.5mm^2 cable via a single
fused connection unit (and certainly not with a cooker hood), and the
cable would be more than adequately fault protected by a B32 MCB at the
origin of the circuit.
sm_jamieson
wrote:
OK, since the main radial circuit wiring will all be surface wired
with socket boxes in the back of cupboards, I can just run the radial
branch to the nearest socket instead of to a junction box.
I sort of didn't quite think of that for some reason. I was imagining
having to run vertically from a yet-to-be positioned socket.
Are three 4mm2 cables connected in a socket box likely to be crowded ?
Thanks,
Simon.
sm_jamieson
> On 12/04/2011 22:59, dennis@home wrote:
>
>
>
>
>
> >news:z66dnaCOspuVJTnQ...@brightview.co.uk...
> >> On 12/04/2011 21:17, ARWadsworth wrote:
I tried to say that in the OP, but used the wrong terminology.
I said "inaccessible-type junction box". I should have said
"maintenance free".
Which kind of shifts the argument.
The debate is then between a maintenance free junction box when the
spur could reasonably be taked from a nearby socket (even if you have
to run horizontally a bit further to reach the socket).
This makes the argument about spurs, and not about accessible junction
boxes ;-)
Simon.
John Rumm
Yup that sounds better.
> I sort of didn't quite think of that for some reason. I was imagining
> having to run vertically from a yet-to-be positioned socket.
> Are three 4mm2 cables connected in a socket box likely to be crowded ?
Yes very, however it varies with the brand of the accessory - some have
more terminal space than others. However you actually only need 2 x 4mm
and 1 x 2.5mm, which should be a bit easier.
John Rumm
Indeed. However if you already have a close by accessory, then there is
not much to be gained from adding an extra JB other than cost.
(Although wago push wire terminals in an empty box may be easier to use
with a larger number of stiff wires - so probably easier to wire a
branch (i.e. 4mm^2) rather than at a socket).
> The debate is then between a maintenance free junction box when the
> spur could reasonably be taked from a nearby socket (even if you have
> to run horizontally a bit further to reach the socket).
> This makes the argument about spurs, and not about accessible junction
> boxes ;-)
Well there is nothing to argue about when the spur is feeding a single
FCU and nothing else - even in dennis land ;-)
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:s4mdnZCYS-Z9TznQ...@brightview.co.uk...
> The spur would obviously be perfectly safe (yes even to you denis), since
> it would not be feasible to overload a 2.5mm^2 cable via a single fused
> connection unit (and certainly not with a cooker hood),
Well at least you realise that you have to qualify what the load is to
"know" its safe, that's progress I suppose.
Unlike the situation where somebody can plug in a four way and overload the
circuit without you having any control over the load on the installation you
did.
> and the cable would be more than adequately fault protected by a B32 MCB
> at the origin of the circuit.
Ah those words again, "adequately fault protected" but not against overload
(strange that that isn't a fault?) should someone put a 13A socket on a 2.5
mm spur and then plug in a four way.
I do like the words electricians use when they blame the user for
overloading their "perfectly protected" installations, they are usually
something like "well they shouldn't do that", "f'ing idiots", "everybody
knows that you can overload a socket without the fuse ever blowing", "they
deserve to have killed their family by doing that".
All to save a bit of copper.
sm_jamieson
> "John Rumm" <see.my.signat...@nowhere.null> wrote in message
A 4-way plug block is fused, and so is an extension lead.
Simon.
ARWadsworth
As your comment was not relevant to John's point then I suggest that you are
the thick one.
--
Adam
Man at B&Q
>
> news:s4mdnZCYS-Z9TznQ...@brightview.co.uk...
>
> > The spur would obviously be perfectly safe (yes even to you denis), since
> > it would not be feasible to overload a 2.5mm^2 cable via a single fused
> > connection unit (and certainly not with a cooker hood),
>
> Well at least you realise that you have to qualify what the load is to
> "know" its safe, that's progress I suppose.
> Unlike the situation where somebody can plug in a four way and overload the
> circuit without you having any control over the load on the installation you
> did.
>
> > and the cable would be more than adequately fault protected by a B32 MCB
> > at the origin of the circuit.
>
> Ah those words again, "adequately fault protected" but not against overload
> (strange that that isn't a fault?)
You are Jerry AICMFP. You will recall the difference between overload
and fault being explained to you, Jerry, a few weeks ago.
MBQ
dennis@home
"sm_jamieson" <sm_ja...@hotmail.com> wrote in message
news:7905244c-2c1d-4a95...@r19g2000prm.googlegroups.com...
Have a look at what current it takes to blow the fuse and note that it is
frequently higher than the current rating of 2.5 mm2 T&E and that is before
someone has replaced it with a nail because it keeps blowing or has been
unfortunate enough to fit a duff fuse like the ones that have been around
every few years that don't actually work.
I would never rely on a user supplied protection device to protect something
I installed as I know the bloody user will screw it up.
Some will and argue that they are correct while saying I am wrong even
though everything I said to do complies with the same regs they are using to
claim they are correct.
You can choose to do either or even do something not in the regs, after all
the regs are there to help those that don't actually know what they are
doing and provided you do the sums "anything" goes as long as you can prove
its safe. Just don't expect the average electrician to have a clue if its
not to the regs.
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io3qn1$rk5$1...@dont-email.me...
So you are too thick.
ARWadsworth
It is possible to get them in. A deeper backbox is recommended. I wired a
kitchen up last week using 4mm and it was no hardship getting the cables
into a BG socket.
--
Adam
ARWadsworth
"> after all the regs are there to help those that don't actually know
> what they are doing and provided you do the sums "anything" goes as
> long as you can prove its safe. Just don't expect the average
> electrician to have a clue if its not to the regs."
Jesus wept. Do you deliberately write this stuff so that people will take
the piss out of you?
Now who was it that did not know the regs last time this came up?
--
Adam
ARWadsworth
I am beginning to wonder if he is TheScullsters BCO.
--
Adam
John Rumm
>
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:s4mdnZCYS-Z9TznQ...@brightview.co.uk...
>
>> The spur would obviously be perfectly safe (yes even to you denis),
>> since it would not be feasible to overload a 2.5mm^2 cable via a
>> single fused connection unit (and certainly not with a cooker hood),
>
> Well at least you realise that you have to qualify what the load is to
> "know" its safe, that's progress I suppose.
As usual, the point of significance misses you. That being that overload
protection is not required at all in this circumstance, because of the
characteristics of the load.
>> and the cable would be more than adequately fault protected by a B32
>> MCB at the origin of the circuit.
>
> Ah those words again, "adequately fault protected" but not against
> overload (strange that that isn't a fault?) should someone put a 13A
No dennis, as has been explained to you many times, overload current and
fault current are not the same thing, and they require independent
consideration. Much the same that a car's braking performance and its
crash performance are treated separately even though they are both "ways
of stopping".
> socket on a 2.5 mm spur and then plug in a four way.
And the result? Overload still not possible...
However, its a straw man argument, much like saying what if someone
connected an electric shower to the bathroom lighting circuit? Then used
that for justification that all lighting circuits should be wired in
10mm^2 T&E.
> I do like the words electricians use when they blame the user for
> overloading their "perfectly protected" installations, they are usually
These would be the mythical electricians that speak to you in the
quieter moments would it dennis? Keep taking the tablets.
Man at B&Q
wrote:
> "sm_jamieson" <sm_jamie...@hotmail.com> wrote in message
That is so "Jerry", even down to the nail as a fuse.
MBQ
John Rumm
"GET Ultimate" are pretty good for terminal space as well IME.
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io419d$9sv$1...@dont-email.me...
I know the bit of the regs you think I don't. I just don't agree with it. I
am not alone in thinking this.
What's more, I don't have to prove its right as I am not using it.
However its easy to prove the alternative I said is true as in all cases it
exceeds the regs.
There are no circumstances where it would be wrong to use 4 mm2 cable in
place of 2.5 mm2 cable.
There are no occasions where it is unsafe to fit a smaller breaker on a 2.5
mm2 circuit.
You could even use 2.5 mm2 radials as per the later editions of the regs.
These BTW are there to replace rings so even the IEE thinks you are onto a
bad thing.
Give it a few more editions of the regs and you wont be doing what you are
doing now.
Are we going to have the same argument as last time or have you come up with
something new and worth listening to?
I expect not.
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:iMqdnd4gkcVtEDjQ...@brightview.co.uk...
> On 13/04/2011 09:33, dennis@home wrote:
>>
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:s4mdnZCYS-Z9TznQ...@brightview.co.uk...
>>
>>> The spur would obviously be perfectly safe (yes even to you denis),
>>> since it would not be feasible to overload a 2.5mm^2 cable via a
>>> single fused connection unit (and certainly not with a cooker hood),
>>
>> Well at least you realise that you have to qualify what the load is to
>> "know" its safe, that's progress I suppose.
>
> As usual, the point of significance misses you. That being that overload
> protection is not required at all in this circumstance, because of the
> characteristics of the load.
Odd its you that misses the point.
I know about fault conditions and overload is a fault condition.
It doesn't involve hundreds of amps but it will sure destroy cables.
>
>>> and the cable would be more than adequately fault protected by a B32
>>> MCB at the origin of the circuit.
>>
>> Ah those words again, "adequately fault protected" but not against
>> overload (strange that that isn't a fault?) should someone put a 13A
>
> No dennis, as has been explained to you many times, overload current and
> fault current are not the same thing, and they require independent
> consideration.
Yes and I don't like the way you do it.
> Much the same that a car's braking performance and its crash performance
> are treated separately even though they are both "ways of stopping".
What cr@p, but to be expected.
>
>> socket on a 2.5 mm spur and then plug in a four way.
>
> And the result? Overload still not possible...
Of course it is, we have been through it before and I have shown several
ways a user can get more than 40A through your 26 amp cable, you just state
"its the users fault", etc.
I just make it impossible without him altering the installation.
>
> However, its a straw man argument, much like saying what if someone
> connected an electric shower to the bathroom lighting circuit? Then used
> that for justification that all lighting circuits should be wired in
> 10mm^2 T&E.
That's altering the installation and also a very bad choice as the breaker
in the lighting circuit would protect it against overload unlike the 2.5 mm2
spurs on rings.
You really should know that as it pretty basic stuff!
You are arguing against things I have never said and it makes you look bad.
I suggest you start again and try to understand the basic argument before
adding in cr@p arguments.
ARWadsworth
> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
> news:io419d$9sv$1...@dont-email.me...
>> dennis@home <den...@killspam.kickass.net> wrote:
>>
>>
>> "> after all the regs are there to help those that don't actually
>> know
>>> what they are doing and provided you do the sums "anything" goes as
>>> long as you can prove its safe. Just don't expect the average
>>> electrician to have a clue if its not to the regs."
>>
>> Jesus wept. Do you deliberately write this stuff so that people will
>> take the piss out of you?
>>
>> Now who was it that did not know the regs last time this came up?
>
> I know the bit of the regs you think I don't.
Of course you now know that bit of the regs. I pointed it out to you last
time around around. That is why I said "did not know last time"
> I just don't agree with
> it. I am not alone in thinking this.
> What's more, I don't have to prove its right as I am not using it.
>
> However its easy to prove the alternative I said is true as in all
> cases it exceeds the regs.
> There are no circumstances where it would be wrong to use 4 mm2 cable
> in place of 2.5 mm2 cable.
> There are no occasions where it is unsafe to fit a smaller breaker on
> a 2.5 mm2 circuit.
Is there a point to those statements?
> You could even use 2.5 mm2 radials as per the later editions of the
> regs. These BTW are there to replace rings so even the IEE thinks you
> are onto a bad thing.
> Give it a few more editions of the regs and you wont be doing what
> you are doing now.
I will adapt to now regs when they occur in reallty not in dennise world.
> Are we going to have the same argument as last time or have you come
> up with something new and worth listening to?
You were proven wrong last time.
> I expect not.
Why don't you go and set fire to an induction hob?
--
Adam
John Rumm
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:iMqdnd4gkcVtEDjQ...@brightview.co.uk...
>> On 13/04/2011 09:33, dennis@home wrote:
>>>
>>>
>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>> news:s4mdnZCYS-Z9TznQ...@brightview.co.uk...
>>>
>>>> The spur would obviously be perfectly safe (yes even to you denis),
>>>> since it would not be feasible to overload a 2.5mm^2 cable via a
>>>> single fused connection unit (and certainly not with a cooker hood),
>>>
>>> Well at least you realise that you have to qualify what the load is to
>>> "know" its safe, that's progress I suppose.
>>
>> As usual, the point of significance misses you. That being that
>> overload protection is not required at all in this circumstance,
>> because of the characteristics of the load.
>
> Odd its you that misses the point.
> I know about fault conditions and overload is a fault condition.
The wiring regs define the terms fault current and overload current. One
is not a subset of the other. Since we are using them here in their
"official" sense, the fact that you would like to define them
differently is not relevant.
The reason they define them separately is that there are fundamental
differences, and in particular the mode of cable heating under fault
conditions must be treated as being adiabatic - this obviously does not
apply to a longer term overloads.
The current carrying capacity of a cable for the point of view of
assessing overload depends heavily on the installation method. While for
fault conditions the method is irrelevant.
An overload (where it is possible to have one) can be "fixed" by
removing the excess load. Fault conditions tend to require more invasive
repair operations.
> It doesn't involve hundreds of amps but it will sure destroy cables.
An overload if permitted for long enough will damage a cable. However
its not relevant in this case.
>>>> and the cable would be more than adequately fault protected by a B32
>>>> MCB at the origin of the circuit.
>>>
>>> Ah those words again, "adequately fault protected" but not against
>>> overload (strange that that isn't a fault?) should someone put a 13A
>>
>> No dennis, as has been explained to you many times, overload current
>> and fault current are not the same thing, and they require independent
>> consideration.
>
> Yes and I don't like the way you do it.
Well you do it your way, I and I will do it the right way...
>> Much the same that a car's braking performance and its crash
>> performance are treated separately even though they are both "ways of
>> stopping".
>
> What cr@p, but to be expected.
So you are suggesting that having just the one drum brake on one wheel
will be adequate, because we have crumple zones and air bags? Or no need
for a laminated screen, because the hand brake is really good?
Strange boy...
>>> socket on a 2.5 mm spur and then plug in a four way.
>>
>> And the result? Overload still not possible...
>
> Of course it is, we have been through it before and I have shown several
Dennis, engage your brain and focus a little before typing will you?
We are talking about a dedicated spur to feed a cooker hood. Total load
is very unlikely to exceed 3A. There will be a FCU at the end of the
spur, with a 3A fuse to protect the flex into the cooker hood. How do
you suppose that this arrangement is going to draw the sustained 40A or
so required to damage the spur cable? Remember there are no sockets,
there is nothing a "user" can do to change the load. I am not aware if
any cooker hood, come induction welders on the market - so even a swap
for a new cooker hood is not going to change the situation.
Hence we can deduce that overload is not a problem we need to worry
about in this scenario. All we need to do is ensure we have fault
protection, for when some dope comes along and nails a spice rack
through the cable, or tries to poke the wrong sort of bulb into the
cooker hood and shorts the bulb contacts. Here it is easy to calculate
the minimum conductor sizes required to ensure the flex to the cooker
hood is not damaged before its protective 3A fuse blows, and the spur
cable and main radial cables back to the CU are not damaged before the
MCB at the origin of the circuit operates.
Now for the avoidance of doubt, I am not saying that treating this feed
as a branch of the radial, and doing it in 4mm^2 cable would be unsafe
or unsatisfactory, just unnecessary.
> ways a user can get more than 40A through your 26 amp cable, you just
You seem to be wandering off at a tangent again - cooker hood on a FCU
remember?
However if you want to talk about sockets...
As has been demonstrated by the ESCs research, the 4 way extension leads
are the primary cause of concern since they typically will not carry a
20A load for any time without catastrophic failure. (many won't even
carry 13A). However one of these, fully loaded on a typical spur will
not damage the spur cable[1] - even if it lasted long enough.
Two of these connected to a double socket (remember these are rated at a
nominal 20A total load - not 26A) - would be bad news - for the socket.
The supply cable is going to be the least of the problems.
[1] Remeber one of the design exercises for the installer using a spur
is that the installation conditions don't de-rate the cable to an
inappropriate amount.
> state "its the users fault", etc.
> I just make it impossible without him altering the installation.
Most of your supposed "problems" involve modification of the
installation one way or another - removing cooker hood feeds, grafting a
pair of four way extension leads onto the wire because you think the
cupboard above the cooker hood would be a really nifty place to stick 8
extra sockets so that you can plug in an additional 9.2kW of load. What
was that going to be again?
> You are arguing against things I have never said and it makes you look bad.
Whereas its the things you have said that makes you look, well not so
much bad, as just rather unhinged and comical.
> I suggest you start again and try to understand the basic argument
> before adding in cr@p arguments.
Good advice - you should practice what you preach.
jgharston
As it says in my copy of Parker-Morris: "socket outlets have obviously
been placed in locations to save wire rather than with consideration
to where they would be useful" ;)
JGH
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io4a8a$lvq$1...@dont-email.me...
> dennis@home <den...@killspam.kickass.net> wrote:
>> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
>> news:io419d$9sv$1...@dont-email.me...
>>> dennis@home <den...@killspam.kickass.net> wrote:
>>>
>>>
>>> "> after all the regs are there to help those that don't actually
>>> know
>>>> what they are doing and provided you do the sums "anything" goes as
>>>> long as you can prove its safe. Just don't expect the average
>>>> electrician to have a clue if its not to the regs."
>>>
>>> Jesus wept. Do you deliberately write this stuff so that people will
>>> take the piss out of you?
>>>
>>> Now who was it that did not know the regs last time this came up?
>>
>> I know the bit of the regs you think I don't.
>
> Of course you now know that bit of the regs. I pointed it out to you last
> time around around. That is why I said "did not know last time"
The only thing you pointed out was that I didn't explicitly state 22A
radials and you went on about 30/32A radials which had nothing to do with
what I said.
But that's typical of you.
>
>> I just don't agree with
>> it. I am not alone in thinking this.
>> What's more, I don't have to prove its right as I am not using it.
>>
>> However its easy to prove the alternative I said is true as in all
>> cases it exceeds the regs.
>
>> There are no circumstances where it would be wrong to use 4 mm2 cable
>> in place of 2.5 mm2 cable.
>> There are no occasions where it is unsafe to fit a smaller breaker on
>> a 2.5 mm2 circuit.
>
> Is there a point to those statements?
>
>> You could even use 2.5 mm2 radials as per the later editions of the
>> regs. These BTW are there to replace rings so even the IEE thinks you
>> are onto a bad thing.
>> Give it a few more editions of the regs and you wont be doing what
>> you are doing now.
>
> I will adapt to now regs when they occur in reallty not in dennise world.
>
>> Are we going to have the same argument as last time or have you come
>> up with something new and worth listening to?
>
> You were proven wrong last time.
Not a chance, you just keep saying that, the reality is different.
>
>> I expect not.
>
> Why don't you go and set fire to an induction hob?
That would be hard to do, why don't you tell me the best way?
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:VaidnUJQiv5YUDjQ...@brightview.co.uk...
> On 13/04/2011 14:48, dennis@home wrote:
>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message>>> On
No you are not.
the second you and adam posted about me and my previous posts you went into
2.5 mm spurs and all the previous arguments.
I even said that at least you defined the load, so were correct in this
case.
that doesn't make all the previous cr@p you posted correct.
> There will be a FCU at the end of the spur, with a 3A fuse to protect the
> flex into the cooker hood. How do you suppose that this arrangement is
> going to draw the sustained 40A or so required to damage the spur cable?
> Remember there are no sockets, there is nothing a "user" can do to change
> the load. I am not aware if any cooker hood, come induction welders on the
> market - so even a swap for a new cooker hood is not going to change the
> situation.
>
> Hence we can deduce that overload is not a problem we need to worry about
> in this scenario. All we need to do is ensure we have fault protection,
> for when some dope comes along and nails a spice rack through the cable,
> or tries to poke the wrong sort of bulb into the cooker hood and shorts
> the bulb contacts. Here it is easy to calculate the minimum conductor
> sizes required to ensure the flex to the cooker hood is not damaged before
> its protective 3A fuse blows, and the spur cable and main radial cables
> back to the CU are not damaged before the MCB at the origin of the circuit
> operates.
>
> Now for the avoidance of doubt, I am not saying that treating this feed as
> a branch of the radial, and doing it in 4mm^2 cable would be unsafe or
> unsatisfactory, just unnecessary.
>
>> ways a user can get more than 40A through your 26 amp cable, you just
>
> You seem to be wandering off at a tangent again - cooker hood on a FCU
> remember?
Its you and adam that want this discussion, I didn't bring it up.
>
> However if you want to talk about sockets...
>
> As has been demonstrated by the ESCs research, the 4 way extension leads
> are the primary cause of concern since they typically will not carry a 20A
> load for any time without catastrophic failure. (many won't even carry
> 13A). However one of these, fully loaded on a typical spur will not damage
> the spur cable[1] - even if it lasted long enough.
>
> Two of these connected to a double socket (remember these are rated at a
> nominal 20A total load - not 26A) - would be bad news - for the socket.
> The supply cable is going to be the least of the problems.
>
> [1] Remeber one of the design exercises for the installer using a spur is
> that the installation conditions don't de-rate the cable to an
> inappropriate amount.
>
>> state "its the users fault", etc.
>> I just make it impossible without him altering the installation.
>
> Most of your supposed "problems" involve modification of the installation
> one way or another - removing cooker hood feeds, grafting a pair of four
> way extension leads onto the wire because you think the cupboard above the
> cooker hood would be a really nifty place to stick 8 extra sockets so that
> you can plug in an additional 9.2kW of load. What was that going to be
> again?
You are going off on another tangent, again.
>
>> You are arguing against things I have never said and it makes you look
>> bad.
>
> Whereas its the things you have said that makes you look, well not so much
> bad, as just rather unhinged and comical.
>
>> I suggest you start again and try to understand the basic argument
>> before adding in cr@p arguments.
>
> Good advice - you should practice what you preach.
Your not going to comment on your error about showers on lighting circuits
then?
I would have thought you would know that they were fully protected against
overload at the CU unlike rings.
ARWadsworth
>>>> Jesus wept. Do you deliberately write this stuff so that people
>>>> will take the piss out of you?
>>>>
>>>> Now who was it that did not know the regs last time this came up?
>>>
>>> I know the bit of the regs you think I don't.
>>
>> Of course you now know that bit of the regs. I pointed it out to you
>> last time around around. That is why I said "did not know last time"
>
> The only thing you pointed out was that I didn't "explicitly state" 22A
> radials and you went on about 30/32A radials which had nothing to do
> with what I said.
> But that's typical of you.
Swap "explicitly state" for "know"
You had no idea that a 2.5mm spur was allowed from a 4mm 30/32A radial
circuit.
>> Why don't you go and set fire to an induction hob?
>
> That would be hard to do, why don't you tell me the best way?
It was you that set fire to the Ł1.99 wok using an induction hob, not me.
--
Adam
ARWadsworth
> Its you and adam that want this discussion, I didn't bring it up.
No. I brought the subject and your name up, not John. However it was the
same OP that started both threads.
You made it a discusson by talking bollocks again and saying that you know
better than BS7671.
Dennise, you are just a figure of fun for the rest of the newsgroup.
Get a life you sad old wanker.
--
Adam
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io51ut$rlg$1...@dont-email.me...
> dennis@home <den...@killspam.kickass.net> wrote:
>
>>>>> Jesus wept. Do you deliberately write this stuff so that people
>>>>> will take the piss out of you?
>>>>>
>>>>> Now who was it that did not know the regs last time this came up?
>>>>
>>>> I know the bit of the regs you think I don't.
>>>
>>> Of course you now know that bit of the regs. I pointed it out to you
>>> last time around around. That is why I said "did not know last time"
>>
>> The only thing you pointed out was that I didn't "explicitly state" 22A
>> radials and you went on about 30/32A radials which had nothing to do
>> with what I said.
>> But that's typical of you.
>
> Swap "explicitly state" for "know"
>
> You had no idea that a 2.5mm spur was allowed from a 4mm 30/32A radial
> circuit.
I didn't care and still don't care, it made no difference to my argument and
still doesn't.
>
>
>>> Why don't you go and set fire to an induction hob?
>>
>> That would be hard to do, why don't you tell me the best way?
>
> It was you that set fire to the Ł1.99 wok using an induction hob, not me.
We that was hot oil in a wok, somewhat different to a hob. I knew you were a
bit thick but I expected you to know the difference.
ARWadsworth
> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
> news:io51ut$rlg$1...@dont-email.me...
>> dennis@home <den...@killspam.kickass.net> wrote:
>>
>>>>>> Jesus wept. Do you deliberately write this stuff so that people
>>>>>> will take the piss out of you?
>>>>>>
>>>>>> Now who was it that did not know the regs last time this came up?
>>>>>
>>>>> I know the bit of the regs you think I don't.
>>>>
>>>> Of course you now know that bit of the regs. I pointed it out to
>>>> you last time around around. That is why I said "did not know last
>>>> time"
>>>
>>> The only thing you pointed out was that I didn't "explicitly state"
>>> 22A radials and you went on about 30/32A radials which had nothing
>>> to do with what I said.
>>> But that's typical of you.
>>
>> Swap "explicitly state" for "know"
>>
>> You had no idea that a 2.5mm spur was allowed from a 4mm 30/32A
>> radial circuit.
>
> I didn't care and still don't care, it made no difference to my
> argument and still doesn't.
Best not admit that you were wrong then.
>>
>>
>>>> Why don't you go and set fire to an induction hob?
>>>
>>> That would be hard to do, why don't you tell me the best way?
>>
>> It was you that set fire to the Ł1.99 wok using an induction hob,
>> not me.
>
> We that was hot oil in a wok, somewhat different to a hob. I knew you
> were a bit thick but I expected you to know the difference.
Everyone else seems to manage not to set fire to their Ł1.99 woks using
their cheap induction hobs.
--
Adam
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io52i2$3bp$1...@dont-email.me...
> dennis@home <den...@killspam.kickass.net> wrote:
>
>> Its you and adam that want this discussion, I didn't bring it up.
>
> No. I brought the subject and your name up, not John.
John also posted a similar comment.
> However it was the same OP that started both threads.
>
> You made it a discusson by talking bollocks again and saying that you know
> better than BS7671.
>
> Dennise, you are just a figure of fun for the rest of the newsgroup.
That's their loss then.
> Get a life you sad old wanker.
Its you that keeps trying to prove me wrong and failing.
Why don't you get a life and give up.
ARWadsworth
> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
> news:io52i2$3bp$1...@dont-email.me...
>> dennis@home <den...@killspam.kickass.net> wrote:
>>
>>> Its you and adam that want this discussion, I didn't bring it up.
>>
>> No. I brought the subject and your name up, not John.
>
> John also posted a similar comment.
No. He replied to my post with a humourous comment. Not quite the same thing
is it?
>> However it was the same OP that started both threads.
>>
>> You made it a discusson by talking bollocks again and saying that
>> you know better than BS7671.
>>
>> Dennise, you are just a figure of fun for the rest of the newsgroup.
>
> That's their loss then.
That does not make sense. Did you write that just to amuse everyone?
>> Get a life you sad old wanker.
>
> Its you that keeps trying to prove me wrong and failing.
I have won every time.
> Why don't you get a life and give up.
Why do you not give up your sad life? I am a real person that does not hide
behind an anonymous name.
--
Adam
dennis@home
"ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
news:io53nf$hbg$1...@dont-email.me...
> dennis@home <den...@killspam.kickass.net> wrote:
>> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
>> news:io52i2$3bp$1...@dont-email.me...
>>> dennis@home <den...@killspam.kickass.net> wrote:
>>>
>>>> Its you and adam that want this discussion, I didn't bring it up.
>>>
>>> No. I brought the subject and your name up, not John.
>>
>> John also posted a similar comment.
>
> No. He replied to my post with a humourous comment. Not quite the same
> thing is it?
No, not humorous at all.
ARWadsworth
> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
> news:io53nf$hbg$1...@dont-email.me...
>> dennis@home <den...@killspam.kickass.net> wrote:
>>> "ARWadsworth" <adamwa...@blueyonder.co.uk> wrote in message
>>> news:io52i2$3bp$1...@dont-email.me...
>>>> dennis@home <den...@killspam.kickass.net> wrote:
>>>>
>>>>> Its you and adam that want this discussion, I didn't bring it up.
>>>>
>>>> No. I brought the subject and your name up, not John.
>>>
>>> John also posted a similar comment.
>>
>> No. He replied to my post with a humourous comment. Not quite the
>> same thing is it?
>
> No, not humorous at all.
Figures of fun have no sense of humor. The reason is because we are laughing
at you not with you.
--
Adam
John Rumm
>
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> On 13/04/2011 14:48, dennis@home wrote:
>>>>> socket on a 2.5 mm spur and then plug in a four way.
>>>>
>>>> And the result? Overload still not possible...
>>>
>>> Of course it is, we have been through it before and I have shown several
>>
>> Dennis, engage your brain and focus a little before typing will you?
>>
>> We are talking about a dedicated spur to feed a cooker hood. Total
>> load is very unlikely to exceed 3A.
>
> No you are not.
> the second you and adam posted about me and my previous posts you went
> into 2.5 mm spurs and all the previous arguments.
I made no mention of your previous posts. I am just trying to get you to
focus on the question at hand.
>>> ways a user can get more than 40A through your 26 amp cable, you just
>>
>> You seem to be wandering off at a tangent again - cooker hood on a FCU
>> remember?
>
> Its you and adam that want this discussion, I didn't bring it up.
You are the one who mentioned "40A through your 26 amp cable" [sic]...
>> However if you want to talk about sockets...
>>
>> As has been demonstrated by the ESCs research, the 4 way extension
>> leads are the primary cause of concern since they typically will not
>> carry a 20A load for any time without catastrophic failure. (many
>> won't even carry 13A). However one of these, fully loaded on a typical
>> spur will not damage the spur cable[1] - even if it lasted long enough.
>>
>> Two of these connected to a double socket (remember these are rated at
>> a nominal 20A total load - not 26A) - would be bad news - for the
>> socket. The supply cable is going to be the least of the problems.
>>
>> [1] Remeber one of the design exercises for the installer using a spur
>> is that the installation conditions don't de-rate the cable to an
>> inappropriate amount.
>>
>>> state "its the users fault", etc.
>>> I just make it impossible without him altering the installation.
>>
>> Most of your supposed "problems" involve modification of the
>> installation one way or another - removing cooker hood feeds, grafting
>> a pair of four way extension leads onto the wire because you think the
>> cupboard above the cooker hood would be a really nifty place to stick
>> 8 extra sockets so that you can plug in an additional 9.2kW of load.
>> What was that going to be again?
>
> You are going off on another tangent, again.
Oh, so you don't want to talk about "40A through your 26 amp cable"
[sic] - ok so why mention it?
>>> You are arguing against things I have never said and it makes you
>>> look bad.
>>
>> Whereas its the things you have said that makes you look, well not so
>> much bad, as just rather unhinged and comical.
>>
>>> I suggest you start again and try to understand the basic argument
>>> before adding in cr@p arguments.
>>
>> Good advice - you should practice what you preach.
>
> Your not going to comment on your error about showers on lighting
> circuits then?
Its not an error dennis, it is something called hyperbole - a bold and
obvious exaggeration intended to parody your keenness to over engineer
everything regardless of technical merit.
> I would have thought you would know that they were fully protected
> against overload at the CU unlike rings.
Are they? Odd that because shower circuits are another good example of a
situation where overload protection is not actually required since there
are no likely failure modes or user actions that could result in
overload. So long as the cable's current continuous rating exceeds the
maximum demand of the shower, you can even have the circumstance where
the MCBs nominal trip current is higher than that of the cables.
Something to beware of when upgrading a shower to a more powerful one.
Andy Wade
> There are no circumstances where it would be wrong to use 4 mm2 cable in
> place of 2.5 mm2 cable.
> There are no occasions where it is unsafe to fit a smaller breaker on a
> 2.5 mm2 circuit.
Both statements are incorrect, IMO, if taken literally.
It would be wrong to use 4 mm^2 cable in place of 2.5 if the enclosure
and or the terminals were too small to avoid bending the conductors
excessively tightly and/or to make sound connections.
It would be unsafe to fit a smaller breaker if this introduced the risk
of tripping and the loss of power introduced danger - e.g. on lighting
circuits.
--
Andy
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:DoednRQozOF4szvQ...@brightview.co.uk...
> On 13/04/2011 21:33, dennis@home wrote:
>>
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:VaidnUJQiv5YUDjQ...@brightview.co.uk...
>>> On 13/04/2011 14:48, dennis@home wrote:
>
>>>>>> socket on a 2.5 mm spur and then plug in a four way.
>>>>>
>>>>> And the result? Overload still not possible...
>>>>
>>>> Of course it is, we have been through it before and I have shown
>>>> several
>>>
>>> Dennis, engage your brain and focus a little before typing will you?
>>>
>>> We are talking about a dedicated spur to feed a cooker hood. Total
>>> load is very unlikely to exceed 3A.
>>
>> No you are not.
>> the second you and adam posted about me and my previous posts you went
>> into 2.5 mm spurs and all the previous arguments.
>
> I made no mention of your previous posts. I am just trying to get you to
> focus on the question at hand.
Both you and adam bought up our previous discussion about spurs in a manner
claiming i was wrong.
You appear to think it applies here.
I never said what you were doing here was wrong.
> Its not an error dennis, it is something called hyperbole - a bold and
> obvious exaggeration intended to parody your keenness to over engineer
> everything regardless of technical merit.
Now you are trying to divert attention from your error.
It would make no difference to the safety of the lighting circuit if someone
did wire the shower to it.
The protection mechanism designed into lighting circuits will protect the
circuit from the excess load.
There is no need to over engineer anything as it is already correctly
engineered.
A point you obviously didn't know when you posted.
However if you connected exactly the same shower to a 2.5 mm2 spur (much
bigger cable than lighting circuits) or even to the actual 2.5 mm2 ring then
its not safe and not adequately protected either.
There are allsorts of rules that the user has to apply to make rings and
ring spurs safe, some of which have changed over the years.
How many homes have spurs with two sockets on spurs? This used to be in the
regs when the IEE thought it was safe. Now it is regarded as unsafe and you
can only fit one. Even this is just a compromise.
>
>> I would have thought you would know that they were fully protected
>> against overload at the CU unlike rings.
>
> Are they? Odd that because shower circuits
Who is talking about shower circuits?
> are another good example of a situation where overload protection is not
> actually required since there are no likely failure modes or user actions
> that could result in overload. So long as the cable's current continuous
> rating exceeds the maximum demand of the shower, you can even have the
> circumstance where the MCBs nominal trip current is higher than that of
> the cables. Something to beware of when upgrading a shower to a more
> powerful one.
So you have never seen a shower where part of the heating element has
shorted, lowering the resistance and increasing the load.
Opps that's another fault condition you don't appear to know can happen.
Then there is the simple upgrade as you state.
Serious overload potential if they have done as you stated is OK and fitted
a higher current breaker than the cable as you have just stated is perfectly
safe.
At least if you do the job correctly in the first place, and fit a breaker
that's less than the cable capacity, the incorrectly fitted wrong shower
will keep tripping the circuit. This should alert the user that something is
wrong and is safe other than getting cold showers.
Doing as you stated was safe on the other hand will not result in the user
noticing as it won't trip, they won't get cold showers. However the cable
will heat up and depending on how long the user showers for may melt and do
other things. With luck it would just short and trip your over rated
breaker, I wouldn't like to rely on that failure mode to ensure safety
myself.
Fitting a breaker that is higher than the cables capacity always leads to
potentially unsafe conditions being introduced without the user knowing.
This applies to 2.5 mm2 spurs and rings no matter what you claim.
Their safety comes from a long list of don't do that, don't do that, etc.
and we all know people obey all the rules don't we! Even people that don't
know what the rules are.
You can continue to follow the minimum the regs say, I don't care, I will
not do electrical work to the minimum standard.
I know how to make circuits safer and I will continue to do so. It costs
peanuts to fit bigger cables and/or smaller breakers to fully protect
circuits and that's what I will continue to do. The IEE haven't convinced me
that what you claim is safe enough so you have no chance, especially in view
of the obvious safety errors you keep making in your posts.
I suggest you stop digging.
ARWadsworth
> You can continue to follow the minimum the regs say, I don't care, I
> will not do electrical work to the minimum standard.
I believe that:-)
--
Adam
John Rumm
>
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:DoednRQozOF4szvQ...@brightview.co.uk...
>> On 13/04/2011 21:33, dennis@home wrote:
>>>
>>>
>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>> news:VaidnUJQiv5YUDjQ...@brightview.co.uk...
>>>> On 13/04/2011 14:48, dennis@home wrote:
>>
>>>>>>> socket on a 2.5 mm spur and then plug in a four way.
>>>>>>
>>>>>> And the result? Overload still not possible...
>>>>>
>>>>> Of course it is, we have been through it before and I have shown
>>>>> several
>>>>
>>>> Dennis, engage your brain and focus a little before typing will you?
>>>>
>>>> We are talking about a dedicated spur to feed a cooker hood. Total
>>>> load is very unlikely to exceed 3A.
>>>
>>> No you are not.
>>> the second you and adam posted about me and my previous posts you went
>>> into 2.5 mm spurs and all the previous arguments.
>>
>> I made no mention of your previous posts. I am just trying to get you
>> to focus on the question at hand.
>
> Both you and adam bought up our previous discussion about spurs in a
I did not mention it. If you think I did, then provide evidence.
> manner claiming i was wrong.
> You appear to think it applies here.
> I never said what you were doing here was wrong.
>> Its not an error dennis, it is something called hyperbole - a bold and
>> obvious exaggeration intended to parody your keenness to over engineer
>> everything regardless of technical merit.
>
> Now you are trying to divert attention from your error.
see above
> However if you connected exactly the same shower to a 2.5 mm2 spur (much
> bigger cable than lighting circuits) or even to the actual 2.5 mm2 ring
> then its not safe and not adequately protected either.
The first case, is probably true, and the second probably false. Rings
have overload and fault protection at the origin. Even though connecting
a shower to one is highly undesirable for many reasons, the chances are
it will not cause any damage to the circuit[1] - as is evidenced by the
many bodged installations where this has been done. Generally bad stuff
does not happen. (a 32A MDB will happily supply 40A for 10s of minutes,
and a pair of 2.5mm^2 T&Es will carry the load without damage if there
is not much other load on the circuit).
[1] The normal damage evident is when the connection to the ring is also
made in 2.5mm^2 T&E - then that usually overheats quite seriously at the
terminations. A connection made in a larger cable will often run for
years without notable damage - although the occasional trip of the
circuit breaker would not be unexpected.
> There are allsorts of rules that the user has to apply to make rings and
> ring spurs safe, some of which have changed over the years.
> How many homes have spurs with two sockets on spurs? This used to be in
> the regs when the IEE thought it was safe. Now it is regarded as unsafe
> and you can only fit one. Even this is just a compromise.
What did you have in mind?
The only fundamental change to ring specifications I can think of is the
upgrading of the CPC to 1.5mm^2 - and that was really a follow on from
research into performance of re-wireable fuses.
Having said that, patterns of use and available technology are ever
evolving and changing well, so it is only right and proper that the
wiring reulations keep track of this. So change in itself is often a
good thing.
>>> I would have thought you would know that they were fully protected
>>> against overload at the CU unlike rings.
>>
>> Are they? Odd that because shower circuits
>
> Who is talking about shower circuits?
I was, and you were replying to my comments on them. Short term memory
problem?
>> are another good example of a situation where overload protection is
>> not actually required since there are no likely failure modes or user
>> actions that could result in overload. So long as the cable's current
>> continuous rating exceeds the maximum demand of the shower, you can
>> even have the circumstance where the MCBs nominal trip current is
>> higher than that of the cables. Something to beware of when upgrading
>> a shower to a more powerful one.
>
> So you have never seen a shower where part of the heating element has
> shorted, lowering the resistance and increasing the load.
> Opps that's another fault condition you don't appear to know can happen.
How do you manage to sound like such a prat in so few words? Is is a
natural talent or have you had to practice?
Yes you could get a short in an element, the usual result is either an
earth fault which disconnects the power, or a hot spot which rapidly
blows the element open circuit, or trips the showers thermal cutout. A
significant element resistance reduction that is sustainable for any
meaningful time seems rather harder to conceive.
> Then there is the simple upgrade as you state.
The point of relevance is that even if there is a simple like for like
swap, there is *no* "simple" upgrade. If replacing a shower with a
higher power one, then the installer must go through the design exercise
again, to make sure that it is appropriate.
> Serious overload potential if they have done as you stated is OK and
> fitted a higher current breaker than the cable as you have just stated
> is perfectly safe.
No, I said it was safe with the original shower. If you go changing
stuff, then its your responsibility to ensure it remains safe.
> At least if you do the job correctly in the first place, and fit a
"correctly" as you inappropriately call it, is alas not always an option.
If you have a shower with peak demand of 41A, and cable with a current
carrying capacity of 47A as installed, then the ideal MCB size would be
45A.
The reality is that many makers don't do a 45A MCB so the choice is 40
or 50A. In that circumstance you either have to fit the 40A MCB with the
knowledge that the design current exceeds its rating, or you fit the
50A, and show by measurement and calculation that it provides fault
protection for the cable (which must be provided at the origin of the
circuit), with the knowledge that that since the shower has a lower
maximum demand than the cable, overload prevention is ensured by the
specification of the load.
Obviously if you have the choice of the 45A MCB in the above scenario
then you use that, if you don't then you go for the second option or
replace the circuit cable with 10mm^2 if possible.
> breaker that's less than the cable capacity, the incorrectly fitted
> wrong shower will keep tripping the circuit. This should alert the user
> that something is wrong and is safe other than getting cold showers.
> Doing as you stated was safe on the other hand will not result in the
> user noticing as it won't trip, they won't get cold showers. However the
> cable will heat up and depending on how long the user showers for may
> melt and do other things. With luck it would just short and trip your
> over rated breaker, I wouldn't like to rely on that failure mode to
> ensure safety myself.
Why would you?
You seem to be back to prattling on about altering circuit parameters
without going through the required design process again, and then
complaining that something is out of spec.
If you consider yourself competent to upgrade a shower, then you would
identify the shortcoming of the supply for the more powerful one and
rectify it as a part of the process. Don't whinge if the last installer
provided a safe working setup, and by fiddling you broke it.
> Fitting a breaker that is higher than the cables capacity always leads
> to potentially unsafe conditions being introduced without the user knowing.
Always dennis? Prey tell...
Does that 3A flex on your light pendant always result in an unsafe
condition without you knowing? The reality is the same logic applies -
the MCB provides fault protection for the flex but not overload
protection. The design of bulb holder and the available choice of bulbs
limits the possibility of overload.
> This applies to 2.5 mm2 spurs and rings no matter what you claim.
You may believe that, however there is a vast body of practical
empirical evidence that suggests otherwise. That you choose to carry on
believing it in spite of the evidence says more about you than anything
else.
> Their safety comes from a long list of don't do that, don't do that,
> etc. and we all know people obey all the rules don't we! Even people
> that don't know what the rules are.
There are few rules, and they are not complex. If you don't understand
them, then don't undertake the work.
> You can continue to follow the minimum the regs say, I don't care, I
> will not do electrical work to the minimum standard.
> I know how to make circuits safer and I will continue to do so. It costs
> peanuts to fit bigger cables and/or smaller breakers to fully protect
> circuits and that's what I will continue to do. The IEE haven't
> convinced me that what you claim is safe enough so you have no chance,
I have no desire to convince you one way or the other dennis. By all
means do what you like in your own home.
As to whether your standard of work is safer or otherwise, we can only
take your assertion at face value, and attribute to it the respect it
deserves based on your posting history on these matters.
> especially in view of the obvious safety errors you keep making in your
> posts.
Ah bless...
dennis@home
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:bIOdnTCCmq4znzrQ...@brightview.co.uk...
> On 14/04/2011 09:24, dennis@home wrote:
>>
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:DoednRQozOF4szvQ...@brightview.co.uk...
>>> On 13/04/2011 21:33, dennis@home wrote:
>>>>
>>>>
>>>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>>>> news:VaidnUJQiv5YUDjQ...@brightview.co.uk...
>>>>> On 13/04/2011 14:48, dennis@home wrote:
>>>
>>>>>>>> socket on a 2.5 mm spur and then plug in a four way.
>>>>>>>
>>>>>>> And the result? Overload still not possible...
>>>>>>
>>>>>> Of course it is, we have been through it before and I have shown
>>>>>> several
>>>>>
>>>>> Dennis, engage your brain and focus a little before typing will you?
>>>>>
>>>>> We are talking about a dedicated spur to feed a cooker hood. Total
>>>>> load is very unlikely to exceed 3A.
>>>>
>>>> No you are not.
>>>> the second you and adam posted about me and my previous posts you went
>
>>>> into 2.5 mm spurs and all the previous arguments.
>>>
>>> I made no mention of your previous posts. I am just trying to get you
>>> to focus on the question at hand.
>>
>> Both you and adam bought up our previous discussion about spurs in a
>
> I did not mention it. If you think I did, then provide evidence.
delude yourself if you want.
>
>> manner claiming i was wrong.
>> You appear to think it applies here.
>> I never said what you were doing here was wrong.
>
>>> Its not an error dennis, it is something called hyperbole - a bold and
>>> obvious exaggeration intended to parody your keenness to over engineer
>>> everything regardless of technical merit.
>>
>> Now you are trying to divert attention from your error.
>
> see above
>
>> However if you connected exactly the same shower to a 2.5 mm2 spur (much
>> bigger cable than lighting circuits) or even to the actual 2.5 mm2 ring
>> then its not safe and not adequately protected either.
>
> The first case, is probably true, and the second probably false. Rings
> have overload and fault protection at the origin. Even though connecting a
> shower to one is highly undesirable for many reasons, the chances are it
> will not cause any damage to the circuit[1] - as is evidenced by the many
> bodged installations where this has been done. Generally bad stuff does
> not happen. (a 32A MDB will happily supply 40A for 10s of minutes, and a
> pair of 2.5mm^2 T&Es will carry the load without damage if there is not
> much other load on the circuit).
You had better tell the IEE they are wrong about point loads on a ring then.
It appears that you can prove its safe to do what they specifically tell you
not to do.
Think of how many pence you can save.
>
> [1] The normal damage evident is when the connection to the ring is also
> made in 2.5mm^2 T&E - then that usually overheats quite seriously at the
> terminations. A connection made in a larger cable will often run for years
> without notable damage - although the occasional trip of the circuit
> breaker would not be unexpected.
>
>> There are allsorts of rules that the user has to apply to make rings and
>> ring spurs safe, some of which have changed over the years.
>> How many homes have spurs with two sockets on spurs? This used to be in
>> the regs when the IEE thought it was safe. Now it is regarded as unsafe
>> and you can only fit one. Even this is just a compromise.
>
> What did you have in mind?
>
> The only fundamental change to ring specifications I can think of is the
> upgrading of the CPC to 1.5mm^2 - and that was really a follow on from
> research into performance of re-wireable fuses.
I thought that I stated they reduced the allowed sockets on spurs, maybe you
forgot.
>
> Having said that, patterns of use and available technology are ever
> evolving and changing well, so it is only right and proper that the wiring
> reulations keep track of this. So change in itself is often a good thing.
Yes and I changed it to not use a breaker larger than the cable rating, I
expect you will catch up sooner or later.
>
>>>> I would have thought you would know that they were fully protected
>>>> against overload at the CU unlike rings.
>>>
>>> Are they? Odd that because shower circuits
>>
>> Who is talking about shower circuits?
>
> I was, and you were replying to my comments on them. Short term memory
> problem?
The hell you were, you were talking about connecting showers to lighting
circuits.
If you think that's a shower circuit I think you have a problem, a big
problem and its not just your short term memory.
>
>>> are another good example of a situation where overload protection is
>>> not actually required since there are no likely failure modes or user
>>> actions that could result in overload. So long as the cable's current
>>> continuous rating exceeds the maximum demand of the shower, you can
>>> even have the circumstance where the MCBs nominal trip current is
>>> higher than that of the cables. Something to beware of when upgrading
>>> a shower to a more powerful one.
>>
>> So you have never seen a shower where part of the heating element has
>> shorted, lowering the resistance and increasing the load.
>> Opps that's another fault condition you don't appear to know can happen.
>
> How do you manage to sound like such a prat in so few words? Is is a
> natural talent or have you had to practice?
Well so far you have not been able to prove what I say is wrong.
You have however managed to not know how a lighting circuit would behave if
you connect a shower to it and have managed to state a point load of 40A is
OK on a 2.5 mm2 ring even though the regs tell you its unsafe.
>
> Yes you could get a short in an element, the usual result is either an
> earth fault which disconnects the power, or a hot spot which rapidly blows
> the element open circuit, or trips the showers thermal cutout. A
> significant element resistance reduction that is sustainable for any
> meaningful time seems rather harder to conceive.
So now you are going to guarantee all failure modes on high powered heaters
so they don't break your rules required to make things safe.
we have been here before about needing lots of rules to make your idea of a
safe circuit safe in use.
I still think you are wrong to rely on rules rather than proper protection.
Its the same as your argument that other equipment will fail first ensuring
any overload will be cleared before any circuit damage.
It requires that nobody actually makes quality equipment that doesn't fail,
a very strange way to ensure safety.
>
>> Then there is the simple upgrade as you state.
>
> The point of relevance is that even if there is a simple like for like
> swap, there is *no* "simple" upgrade. If replacing a shower with a higher
> power one, then the installer must go through the design exercise again,
> to make sure that it is appropriate.
What exactly does that have to do with the argument?
That's life.
You are talking about shower circuits not what the argument is about.
According to you I could fit a 100 A (no I haven't done the fault condition
calcs as they don't matter here) breaker in a 10 mm2 circuit and let the
shower limit the load. After all a 40A shower can never take more than 100A
and its all perfectly safe from overload.
>
> If you consider yourself competent to upgrade a shower, then you would
> identify the shortcoming of the supply for the more powerful one and
> rectify it as a part of the process. Don't whinge if the last installer
> provided a safe working setup, and by fiddling you broke it.
Back to blaming others I see.
>
>> Fitting a breaker that is higher than the cables capacity always leads
>> to potentially unsafe conditions being introduced without the user
>> knowing.
>
> Always dennis? Prey tell...
>
> Does that 3A flex on your light pendant always result in an unsafe
> condition without you knowing?
No because I know and use 1.5 mm2 flex.
0.75 mm2 flex is useless.
> The reality is the same logic applies - the MCB provides fault protection
> for the flex but not overload protection. The design of bulb holder and
> the available choice of bulbs limits the possibility of overload.
>
>> This applies to 2.5 mm2 spurs and rings no matter what you claim.
>
> You may believe that, however there is a vast body of practical empirical
> evidence that suggests otherwise. That you choose to carry on believing it
> in spite of the evidence says more about you than anything else.
There is no real investigation into many accidents so I can safely ignore
the empirical evidence.
They just assume they know what caused the incident.
>
>> Their safety comes from a long list of don't do that, don't do that,
>> etc. and we all know people obey all the rules don't we! Even people
>> that don't know what the rules are.
>
> There are few rules, and they are not complex. If you don't understand
> them, then don't undertake the work.
I will ask a pensioner if she knows what the rules are for using trailing
sockets and what they can plug in and use then.
I don't expect here to know but it appears you do.
>
>> You can continue to follow the minimum the regs say, I don't care, I
>> will not do electrical work to the minimum standard.
>> I know how to make circuits safer and I will continue to do so. It costs
>> peanuts to fit bigger cables and/or smaller breakers to fully protect
>> circuits and that's what I will continue to do. The IEE haven't
>> convinced me that what you claim is safe enough so you have no chance,
>
> I have no desire to convince you one way or the other dennis. By all means
> do what you like in your own home.
>
> As to whether your standard of work is safer or otherwise, we can only
> take your assertion at face value, and attribute to it the respect it
> deserves based on your posting history on these matters.
Well the last few posts you have made make me wonder if you actually know
anything about electrics.
ARWadsworth
> Well the last few posts you have made make me wonder if you actually
> know anything about electrics.
All your posts make me wonder if you actually know anything.
--
Adam
John Rumm
I thought about replying, but he seems so tied up in knots now
attempting to win an argument (not actually sure about what, or with
who), that it must be terminally dull for everyone.
He's like dribble but without the charm. (with appologies to dribble!)
ARWadsworth
> On 14/04/2011 20:53, ARWadsworth wrote:
>> dennis@home<den...@killspam.kickass.net> wrote:
>>
>>> Well the last few posts you have made make me wonder if you actually
>>> know anything about electrics.
>>
>> All your posts make me wonder if you actually know anything.
>
> I thought about replying, but he seems so tied up in knots now
> attempting to win an argument (not actually sure about what, or with
> who), that it must be terminally dull for everyone.
>
> He's like dribble but without the charm. (with appologies to dribble!)
Indeed, lets leave be. I have had my fun.
Never try to teach a pig to dance. It will frustrate you, and it irritates
the pig.
--
Adam