CU change what is the exact standing now under the 17th

oharaf · 22 Sep 2008

I have a customer wanting a new CU, They only have 4 circuits

Lights, Upstairs ring final, Down stairs ring final and the cooker.

It is a two up two down!!

Do I have to install a dual RCD board or am I perfectly fine to install an single RCD board with the lights on none RCD side??

The lighting circuit does have a cpc (thank god)

I normally would reccomend a dual RCD CU but in this case it just seems an almost ridiculous, RCD trips no lights!!!

On testing the entire installation is giving excellent readings so suggesting a partial re-wire of the lighting circuit for example seems crazy and they don't really relish the idea of me chasing their walls out!!

Some good clear advice here please chaps

sm1thson · 22 Sep 2008

oharaf said:
am I perfectly fine to install an single RCD board with the lights on none RCD side??

nope, not if the cables are <50mm etc etc (which they 99.9% sure will be).

oharaf said:
I normally would reccomend a dual RCD CU but in this case it just seems an almost ridiculous, RCD trips no lights!!!

I agree a fault on another circuit would take out all the lights (unless you can split the light circuit).

how about a split load single RCD board with the lights on the none RCD side but with their own RCBO? or just RCBOs all round.

holmslaw · 22 Sep 2008

Dual rcd boards do not, and have never complied with regs.

The main bonding to gas and water must be in place, if not you must install.

There are no other requirements to bring circuits up to 17th edition, regs not retroactive. Plus it is impossibe to know how deep cables are buried, a bit of 17th B*****x.

Fit a standard cu (assuming not TT) with rcbos for lighting and power sockets, cooker can be on mcb.

oharaf · 22 Sep 2008

Cheers guys, for some strange reason I forgot the old RCBO!!!!

Probably because when you mention the cost the defribulator is required

That is the solution here

Thanks

holmslaw · 22 Sep 2008

oharaf said:
Probably because when you mention the cost the defribulator is required

That is the solution here

Thanks

Is this job a freebie then!

oharaf · 22 Sep 2008

FingRinal · 22 Sep 2008

Here's my two pennies worth...which might be controversial.

It is the arrangement of circuits that complies or doesn't comply with the 17th. Dual RCD boards can facilitate this compliance, but it's true that there is no such thing as a 17th Edition CU (as has been mentioned).

For a board change nowadays, unless you can prove otherwise, you have to assume that RCD protection is required for all circuits. So all circuits will require it should you change the board.

If you bought a small single split-load board with one RCD, you could put all the circuits except the lights on the RCD side and put the lights on the non RCD side but with an RCBO. To prove whether or not this complies with the 17th is mainly down to the users. What would they perceive to be an inconvenience until someone could fix the cause of the tripping? What would they consider the most hazardous of the permutations? Add in your own experience and you'll have your answer.

I've never quite understood why losing sockets downstairs and not upstairs or vice-versa makes a difference. The temptation is then to run an extension up/down the stairs - a more obvious tripping hazard couldn't be described. Such things tend to stick around longer than they should as people get used to living like that and put off the expense of getting an electrician in to fix the problem.

I don't believe that a competent electrician should advise of only the most expensive options.

ban-all-sheds · 22 Sep 2008

holmslaw said:
There are no other requirements to bring circuits up to 17th edition, regs not retroactive.

FingRinal said:
For a board change nowadays, unless you can prove otherwise, you have to assume that RCD protection is required for all circuits. So all circuits will require it should you change the board.

Well - you can't both be right.

What are your arguments for and against...

oharaf · 22 Sep 2008

FR, pretty much my feelings really, I don't like suggesting the 'expensive' option it is off putting for the customer.

I have decided on the split load with RCBO for the lights or even total RCBO depending on what the customer prefers.

I must say the idea of lighting on a RCD still strikes me as over kill but then again the number of 'lack of common sense' people in the world appears to be growing at an exponential rate!!

It will be the lack of good maths teachers

FingRinal · 22 Sep 2008

ban-all-sheds said:
holmslaw said:

There are no other requirements to bring circuits up to 17th edition, regs not retroactive.

Click to expand...

FingRinal said:

For a board change nowadays, unless you can prove otherwise, you have to assume that RCD protection is required for all circuits. So all circuits will require it should you change the board.

Click to expand...

Well - you can't both be right.

What are your arguments for and against...

My reasoning is included in the bit you've quoted. I'm sorry if it confuses you.

ban-all-sheds · 22 Sep 2008

I'm not confused - I just don't see any reasoning, only an opinion that you are required to bring an existing installation up to 17th standards when changing a CU.

FingRinal · 22 Sep 2008

ban-all-sheds said:
I'm not confused - I just don't see any reasoning, only an opinion that you are required to bring an existing installation up to 17th standards when changing a CU.

I'm afraid you are either confused or being deliberately obtuse and obdurate.

I wonder which?

holmslaw · 22 Sep 2008

FingRinal said:
Dual RCD boards can facilitate this compliance,

They do not comply with reg 314.

EDIT - changed reg no from 413 to 314.

FingRinal said:
I don't believe that a competent electrician should advise of only the most expensive options.

I advised the correct option.

holmslaw · 22 Sep 2008

ban-all-sheds said:
holmslaw said:

There are no other requirements to bring circuits up to 17th edition, regs not retroactive.

Click to expand...

FingRinal said:

For a board change nowadays, unless you can prove otherwise, you have to assume that RCD protection is required for all circuits. So all circuits will require it should you change the board.

Click to expand...

Well - you can't both be right.

What are your arguments for and against...

You pompous p****, another pointless and unhelpful post.

kkynaston · 22 Sep 2008

8W Wylex with 100A Iso : £19.57
2 x 32A RCBO's @ 34.03: £68.06
10A RCBO (Can't see 6's atm) £34.03
edit: I forgot the cooker!!!! so I spose another £35

£102.09 + the dreaded

or 9W Split with 5mcb's £47.06 (then remove 2)
10A RCBO (Can't see 6's atm) £34.03
£81.09 + the dreaded

Forget this after the edit:
I think I would probably go for the whole RCBO board for the extra £20
Looks a lot better but its up to the customer at the end of the day

[/u]

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CU change what is the exact standing now under the 17th

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