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Topic Title: rewirable consumer unit
Topic Summary: change
Created On: 30 May 2007 10:51 PM
Status: Read Only
Linear : Threading : Single : Branch
 rewirable consumer unit   - 120409 - 30 May 2007 10:51 PM  
 rewirable consumer unit   - Jez937 - 30 May 2007 10:57 PM  
 rewirable consumer unit   - 120409 - 31 May 2007 11:33 AM  
 rewirable consumer unit   - normcall - 31 May 2007 07:21 AM  
 rewirable consumer unit   - AJJewsbury - 31 May 2007 01:44 PM  
 rewirable consumer unit   - 120409 - 31 May 2007 02:18 PM  
 rewirable consumer unit   - davebarman - 31 May 2007 03:10 PM  
 rewirable consumer unit   - rocknroll - 31 May 2007 03:36 PM  
 rewirable consumer unit   - 120409 - 31 May 2007 03:46 PM  
 rewirable consumer unit   - Voltimax - 31 May 2007 06:50 PM  
 rewirable consumer unit   - 120409 - 31 May 2007 07:31 PM  
 rewirable consumer unit   - Voltimax - 31 May 2007 08:24 PM  
 rewirable consumer unit   - GaryMo - 02 June 2007 12:59 PM  
 rewirable consumer unit   - deleted_thenewapprentice - 02 June 2007 01:29 PM  
 rewirable consumer unit   - alancapon - 02 June 2007 02:13 PM  
 rewirable consumer unit   - ebee - 02 June 2007 09:05 PM  
 rewirable consumer unit   - weirdbeard - 28 August 2016 03:10 PM  
 rewirable consumer unit   - neilr10 - 03 June 2007 09:02 PM  
 rewirable consumer unit   - den1962 - 01 June 2007 05:07 PM  
 rewirable consumer unit   - AJJewsbury - 01 June 2007 05:14 PM  
 rewirable consumer unit   - den1962 - 02 June 2007 09:19 AM  
 rewirable consumer unit   - alancapon - 02 June 2007 10:36 AM  
 rewirable consumer unit   - GeoffBlackwell - 02 June 2007 12:10 PM  
 rewirable consumer unit   - den1962 - 02 June 2007 11:27 AM  
 rewirable consumer unit   - alancapon - 02 June 2007 11:45 AM  
 rewirable consumer unit   - GaryMo - 02 June 2007 01:37 PM  
 rewirable consumer unit   - deleted_2_tony30 - 02 June 2007 01:59 PM  
 rewirable consumer unit   - alancapon - 02 June 2007 02:19 PM  
 rewirable consumer unit   - megohm - 03 June 2007 10:38 PM  
 rewirable consumer unit   - mark2spark - 03 June 2007 11:05 PM  
 rewirable consumer unit   - mark2spark - 03 June 2007 11:02 PM  
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 30 May 2007 10:51 PM
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120409

Posts: 19
Joined: 27 May 2007

I have been looking at a few jobs for a for a loft conversion company as they need a sparky. 1 lighting circuit, 1 ring circuit and 1 circuit for mains smokes are installed in to the loft area. There has been 6 way rewirable units in the houses and usually the fuses have been doubled up and even three circuits feed from one fuse. I have been advised them to change the consumer unit to a new 10/12 way mcb board etc. they are saying no, just put a 3/5 way supplementary unit in off of a henly block. and leave the existing unit as is due to cost. dont like the idea myself. any advise?
 30 May 2007 10:57 PM
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Jez937

Posts: 510
Joined: 02 January 2006

What categary will you grade the fire alarm / smoke alarm when you certficate it?

Not being an ass, would like to look it up and help you out, if I can?
 31 May 2007 11:33 AM
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120409

Posts: 19
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Grade D Category LD3
 31 May 2007 07:21 AM
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normcall

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One reason why I hate working for builders - they do like to do things their way!

-------------------------
Norman
 31 May 2007 01:44 PM
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AJJewsbury

Posts: 16102
Joined: 13 August 2003

supplementary unit in off of a henly block

Unless there's an switch-disonnector (isolator) before the henleys, you'd not have a single main switch for the installation - 460-01-02.

- Andy.
 31 May 2007 02:18 PM
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120409

Posts: 19
Joined: 27 May 2007

the tails would come from the meter to the henly block then to the main house cu with a main 2 pole isolater, and to the loft supplementary cu with a main 2 pole switch. both protected by main supply company fuse head.
 31 May 2007 03:10 PM
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davebarman

Posts: 285
Joined: 27 February 2006

Those sort of days are well behind us.

If it was my job I would be looking to put in a new split load board and take a sub-main from there to the loft.

Henley Blocks may have their place but I don't believe they should be on the main tails. (how very sixties).

How are you going to singly isolate the supply.

The builder I am sure could get the extra cost that would be involved as an "extra"

Otherwise just don't bother why keep him happy, is he going to sign the cert. I think not!

Regards

Dave

-------------------------
Never knock on Death's door. Ring the doorbell and run like hell, he hates that!

Edited: 31 May 2007 at 03:11 PM by davebarman
 31 May 2007 03:36 PM
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rocknroll

Posts: 9549
Joined: 03 October 2005

I suppose you have to remember is the builder will have put a price in for the electrics and the less he can get you to do the more money he makes, I think its time for 'take it or leave it'.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 31 May 2007 03:46 PM
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120409

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leave it
 31 May 2007 06:50 PM
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Voltimax

Posts: 59
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What exactly is wrong with the practice the builder is suggesting? Have you ever read Brian Scaddans electrical installations publication? In his example of installing a 9KW kiln, he advocates that exact practice. Personally I try never to do this, but I have been advised to do it several times by the NICEIC.

-------------------------
This post has been Chuck Norris Approved.

Edited: 31 May 2007 at 06:51 PM by Voltimax
 31 May 2007 07:31 PM
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120409

Posts: 19
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so you say you dont need an isolator before the henley
 31 May 2007 08:24 PM
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Voltimax

Posts: 59
Joined: 15 July 2006

Originally posted by: 120409

so you say you dont need an isolator before the henley



I never said any such thing. Read my post again.
The publication I speak of is well known and I believe that Mr Scaddan is an honary member of the city & guilds and examiner.
I have pointed out that he has advocated this practice in his book. Therefore I'm asking the question, how is it that he recommends such a practice if it is wrong?

-------------------------
This post has been Chuck Norris Approved.

Edited: 31 May 2007 at 08:32 PM by Voltimax
 02 June 2007 12:59 PM
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GaryMo

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Originally posted by: AJJewsbury

supplementary unit in off of a henly block


Unless there's an switch-disonnector (isolator) before the henleys, you'd not have a single main switch for the installation - 460-01-02.



Reading 460-01-02.....

It also states that where and installation is supplied from more than one source, a main switch shall be provided for each source of supply and a durable warning notice shall be permanently fixed in such a position that any person seeking to operate any of these main switches will be warned of the need to operate all such switches to achieve isolation of the installation.

Could you call 2 CCU's fed from a common henley block to be 2 sources of supply to an installation? Is so then could you get away with suitable warning notices?
 02 June 2007 01:29 PM
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deleted_thenewapprentice

Posts: 5
Joined: 02 June 2007

Are looking to justify a practice that I am sure the majority of us would frown upon if we came across it in the real world

I'm sure it would get a grade 2 on a PIR, it would with our firm anyway.

Regards

Bradley
 02 June 2007 02:13 PM
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alancapon

Posts: 6941
Joined: 27 December 2005

Originally posted by: GaryMo
Could you call 2 CCU's fed from a common henley block to be 2 sources of supply to an installation? Is so then could you get away with suitable warning notices?


One electricity meter = 1 source (unless it is E7, in which case it could conceivably be two sources)

One electricity meter & 1 standby generator = 2 sources


Regars,

Alan.
 02 June 2007 09:05 PM
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ebee

Posts: 6347
Joined: 02 December 2004

Interesting banter here.
Ok radial (lighting circuit say) loop in to 1st rose, from first rose loop out in opposite directions to another two (seperate radials) then from these two each to another two ad infinitum. Well up to circuit maximum for current draw.
A tree (or branch or bush or nightmare to PIR anyway LOL ) but wrong or non complying?
The same circuit with umpteen radials fed from the same fuseway on a board then, does it comply or is it as safe/less safe to a greater or lesser extent?
OK more difficult to I & T but that does not make it right to condem out of hand as many would do IMHO (as well as the I & T you`d actually have to do calcs rather than rely on conventional circuit arrangements as defined in the OSG. Remembering that such not listed as conventional circuits may still be correct to BS 7671 but if you defect them you might actually be sued by the original designer/installer).
Well that`s my take on it.
In brief, unconventional does not always equal incorrect

Reminds me slightly of the wrong circuit thread I did recently in that I might not like it at all but difficult to realistically condem. Gosh though, if life was so simple the we`d all live it easily and learn nowt from others

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Edited: 02 June 2007 at 09:11 PM by ebee
 28 August 2016 03:10 PM
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weirdbeard

Posts: 3116
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Originally posted by: ebee

Interesting banter here.

Ok radial (lighting circuit say) loop in to 1st rose, from first rose loop out in opposite directions to another two (seperate radials) then from these two each to another two ad infinitum. Well up to circuit maximum for current draw.

A tree (or branch or bush or nightmare to PIR anyway LOL ) but wrong or non complying?

The same circuit with umpteen radials fed from the same fuseway on a board then, does it comply or is it as safe/less safe to a greater or lesser extent?

OK more difficult to I & T but that does not make it right to condem out of hand as many would do IMHO (as well as the I & T you`d actually have to do calcs rather than rely on conventional circuit arrangements as defined in the OSG. Remembering that such not listed as conventional circuits may still be correct to BS 7671 but if you defect them you might actually be sued by the original designer/installer).

Well that`s my take on it.

In brief, unconventional does not always equal incorrect



Reminds me slightly of the wrong circuit thread I did recently in that I might not like it at all but difficult to realistically condem. Gosh though, if life was so simple the we`d all live it easily and learn nowt from others


Good advice all round

-------------------------
:beer)
 03 June 2007 09:02 PM
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neilr10

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Joined: 01 March 2006

I agree with Davebarman a suitable size split load unit would be the way to go in an ideal world, but then a periodic cert. for the whole installation would have to be issued.

-------------------------
Electricity is not your friend, it spends its time trapped in an insulated prison, waiting for an opportunity to escape and kill you..
 01 June 2007 05:07 PM
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den1962

Posts: 206
Joined: 09 February 2007

Going back to the first question about 6way rewirable board, having multi circuits from each fuse, don't reg 314-01-04 cover this ?.

just a thought
 01 June 2007 05:14 PM
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AJJewsbury

Posts: 16102
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Going back to the first question about 6way rewirable board, having multi circuits from each fuse, don't reg 314-01-04 cover this ?.

Nope, because the definition of a circuit (see part 2) is anything "protected against overcurrent by the same protective device" - so everything connected to one fuse is therefore the same single circuit - regardless of how many cables there are. (I think you'd have to connect a circuit (e.g. each log of the same ring) to two different fuses or borrow a neutral to contravene 314-01-04).

- Andy.
 02 June 2007 09:19 AM
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den1962

Posts: 206
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andy
it may be the way we both interpret the regs i see each cable coming out of a fuse as a final circuit.
that why it comes under installation of circuit arrangment.
having say 3 or 4 lighting circuits coming out of one fuse which wont blow because its not over load not make it right.

den

now i may be wrong

Edited: 02 June 2007 at 11:20 AM by den1962
 02 June 2007 10:36 AM
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alancapon

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So, fitting a junction box two inches from the consumer unit improves it?


Regards,

Alan.
 02 June 2007 12:10 PM
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GeoffBlackwell

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Originally posted by: den1962

andy

it may be the way we both interpret the regs i see each cable coming out of a fuse as a final circuit.

that why it comes under installation of circuit arrangment.

having say 3 or 4 lighting circuits coming out of one fuse which wont blow because its not over load not make it right.



den

now i may be wrong



Yes you are - wrong that is

We have ring circuits and radial circuits. Some countries have tree circuits - one trunk and then a number of branches.

We are discussing a circuit that consists of a number of radial runs from a CPD - so what will we call it? - A brush circuit, or may be a bush circuit, or you decide - answers on a postcard please.

Remember we can have rings with a spur from the CPD and we could of course have multiple trees from the same CPD .

The point is, as others have pointed out above, we can have anything we like provided it complies with BS 7671 and that means that it has: over current protection, shock protection etc, etc. BS 7671 wisely does not specify the precise format of the circuit (the IEE stopped doing that when the 15th edition came out).

You may call these things bad practice but I recommend that you think carefully about that - what is it that makes them bad?.

Regards

Geoff Blackwell
 02 June 2007 11:27 AM
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den1962

Posts: 206
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no that just makes poor workmanship,as having joint boxes around a consumer unit just because there are no spare ways or fuseholders are crammed with cables.
 02 June 2007 11:45 AM
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alancapon

Posts: 6941
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Exactly. I still agree with Andy's definition of a circuit from earlier though. What is important, and that goes for any termination, is that the number and size of conductors joined should not exceed the manufacturer's recommendations.


Regards,

Alan.
 02 June 2007 01:37 PM
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GaryMo

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Not looking to justify it but looking to see if you agree a warning notice would ensure compliance with BS7671. If that's the case how could you justify a grade 2 on a PIR?
 02 June 2007 01:59 PM
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deleted_2_tony30

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off topic slightly but with a domestic, 24 hour, off peak and bottom immersionsupply this = 4 tails how do you isolate them, remember theres a neutral too.

5 live conductor!!!

regards

tony
 02 June 2007 02:19 PM
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alancapon

Posts: 6941
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Originally posted by: tony30
off topic slightly but with a domestic, 24 hour, off peak and bottom immersionsupply this = 4 tails how do you isolate them, remember theres a neutral too.

5 live conductor!!!


With Economy 7 (or equivalent), we often see a four-pole main switch - often two 2-pole switches with a linking bar on the operating handle. How about three 2-pole switches linked, although you would have to put it in a small consumer unit housing!

The four-pole arrangements are often for flats with a common meter room, and are accomodated in a small consumer unit at the meter position, with two mcbs to protect the extended meter tails (normal & E7).


Regards,

Alan.
 03 June 2007 10:38 PM
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megohm

Posts: 194
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"There has been 6 way rewirable units in the houses and usually the fuses have been doubled up and even three circuits feed from one fuse."

Just checking on my understanding of the Regs.

Is an MCB with multiple final circuits a defect under BS7671 YES/NO ?

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 03 June 2007 11:05 PM
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mark2spark

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Originally posted by: megohm
Is an MCB with multiple final circuits a defect under BS7671 YES/NO ?


I don't understand your definition... I can't see how there can be a multiple final circuit(s) from one MCB?
One MCB = One circuit, IMO.

So my answer to your Q would be no.

-------------------------
I am prone to talking complete bol***ks at times, please accept my apologies in advance.
 03 June 2007 11:02 PM
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mark2spark

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To answer the original Q:
IMO, a warning notice that there is more than one main switch for isolation makes the installation comply.
Not the best practise, agreed, but I can't see where a code 2 comes from.

-------------------------
I am prone to talking complete bol***ks at times, please accept my apologies in advance.
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