Consumer Units.

[sjl468]

Load of small old houses with the an old re-wirable fusebox have say 4/5 circuits. Two for the ring mains, one for the lighting and say a cooker and/or shower. What CU should be used if exchanging the old one? To me it's a bit overboard sticking in a 17th edition one in with two RCD's. Can i still put in one with only one RCD if there are a small number of circuits?
I know the houses should really be re-wired but if all the cables etc are in good condition and the demand is low enough for the breaker it doesn't need it. And i don't like doing work unless it is necessary.

 

[too old to learn]

from what i gather you could have a consumer unit with 12 MCB's in all covered with one RCD and it still meets the 17th edition, the problem with that is the nuisance tripping. if one circuit goes it takes out the whole house.
therefore with only a few circuits you still have the same scenario, one goes the whole house is in darkness, if at night, people can fall and hurt them selves as there is no lights or lamps from sockets etc.
anyhow, im sure there will be now replies saying if im wrong .
but as said, my opinion is as long as all circuits covered with RCD then it meets 17th

 

[EdwardCurrent]

Hello,

Maybe RCBO's would help with 'nuisance' tripping issues ?

Ed

 

[JACKC]

Posted: Tue Jan 13, 2009 9:34 am Post Subject:

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from what i gather you could have a consumer unit with 12 MCB's in all covered with one RCD and it still meets the 17th edition, the problem with that is the nuisance tripping.
IMO not correct.
This type of board did not comply with the 16th and does not comply with the 17th edition. You can buy a dual rcd unit with 8 ways in fron QVS for a few quid and then rearrange your circuits to give the discrimination required. You then have spares for future add on's
http://www.qvsdirect.com/8-Way-Spli...80A-30mA-RCDs-8-MCBs-Split-4-4-pr-23368.html.
You say you know a rewire is required, then why not get a sparkie in to carry out a consumer unit change. A periodic inspection will be carried out before the cons unit is replaced and you will know if a rewire is required by what if any faults are found. You will have peace of mind knowing everything is ok then.

 

[ban-all-sheds]

from what i gather you could have a consumer unit with 12 MCB's in all covered with one RCD and it still meets the 17th edition,

An opinion shared by so few others that it's bound to be wrong.

An opinion which would be viewed by so many householders as wrong that it's bound to be wrong.

the problem with that is the nuisance tripping. if one circuit goes it takes out the whole house.

314.1

therefore with only a few circuits you still have the same scenario, one goes the whole house is in darkness, if at night, people can fall and hurt them selves as there is no lights or lamps from sockets etc.

314.1

anyhow, im sure there will be now replies saying if im wrong .
but as said, my opinion is as long as all circuits covered with RCD then it meets 17th

You yourself have described why it doesn't, so HTH can you think it does?

 

[ban-all-sheds]

JACKC - have a play with this:

 

[JACKC]

JACKC - have a play with this:

Thanks

 

[too old to learn]

Hi BAS,

I aint got a regs book to hand so can you please qoute 314.1 .

 

[ban-all-sheds]

NRN, as I don't have a soft copy - maybe someone who does can copy & paste, but it's the one which refers to minimising inconvenience in the event of a fault, and it makes specific reference to lighting circuits.

 

[too old to learn]

so, you can never fully cover nuisance tripping, well unless you go to RCBO's. therefore is it still not correct in saying that if all circuits are covered by a RCD then it does meet (in a crappy sort of way) 17th edition?
you have a house with one ring circuit (sockets) and 1 radial (lights).
is it then a case that you still need two RCD's or would 1 suffice.

as my name suggests, i am here to learn not to cause conflicts and will always bow down to the more experienced.

Cheers

 

[EdwardCurrent]

I must be bored.


314 DIVISION OF INSTALLATION.

314.1 Every installation shall be divided into circuits, as necessary, to:

(i) avoid hazards and minimize inconvenience in the event of a fault

(ii) facilitate safe inspection, testing and maintenance (see also Section 537)

(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit

(iv) reduce the possibility of unwanted tripping of RCD's due to excessive protective conductor currents produced by equipment in normal operation

(v) mitigate the effects of electromagnetic influences (EMI)

(vi) prevent the indirect energizing of a circuit intended to be isolated.



I'm off to get a life

Ed

 

[too old to learn]

thanks EC.

so simple question then open to one and all,

two circuits in a very small house, poor person only has one room lol. does the light and sockets on one RCD meet 17th edition?

 

[kkynaston]

IF there were only 2 circuits it would be much cheaper to use a Main Switch Incommer and RCBO's

 

[too old to learn]

corect, but im just trying to see opinions on how many circuits can be on one rcd before it doesnt comply with 17th edition.

but i guess thats the probs with the wiring regs, they cant lay it all out in black and white (even though they have ) and it still is open to individual opinions

 

[EdwardCurrent]

Indeed TOTL,

To answer your question (only my opinion mind), if there is more than one MCB covered by an RCD then it doesn't/cannot comply with the 17th. Where if you were to use RCBO's I do think it would 'comply'.

As you say, another 'grey area'.

Regards

Ed