adding new circuit

[ianphilip007]

hello

when adding a new circuit (via spare way) to a existing CU with a 30ma rcd main switch (we cant change the board all the time or fit rcbo), do you note as a deviation on cert re (regulation 314) or not write anything ?

many thanks

 

[Snapester]

30mA main switch? Is it a TT installation? I would say that it wouldn't comply with 314.1 as surely this would cause danger if the whole installation was to lose power i would say the main switch should be a time delay RCD if anything.

 

[ianphilip007]

no not a tt system its a tncs. accept that compliance with 314.1 is not being met, so my question is do you note this as a deviation on cert and advise customer accordingly? ( exisiting board/installation installed to different regulations. 17th not retrospective)

 

[pencilpusher]

Why a time delayed RCD? There is no other RCD to worry about re discrimination. I would say a 30ma RCD gives the additional protection that was already there and is required. I would add the circuit and make a note of what I have done and my considerations on the cert (but then I do write everything down!) I would discuss with customer and expain and note it. Your added circuit will comply with the latest regs. A new board would be ideal (isn't it always) but not necessary IMO. That is my thinking anyway!

 

[ezzzekiel]

The circuit you have added has rcd protection so can't see a problem

 

[Snapester]

Reg. 314 states that it must not cause danger if a fault occurs on one circuit? With a standard non time delayed RCD main switch surely this would cause the whole house to black out if a single fault occurs on any circuit?

 

[ianphilip007]

that was my thinking too, note on cert as to what has been done and re (314.1) advise customer re nusicance tripping due to single rcd, new board would be grt but not always possible or needed. additional circuit will meet 17th regs as required (rcd protected) existing installation is not required to meet current 17th regs and in my opinion this is where reg (314.1) should be applied to the exisiting CU which predates the 17th.

 

[drew35]

Don't all the lights go out when there's a power cut? Or are they against regs also?

 

[ipf]

You didn't design or install the existing installation. Responsible for the circuit you're installing. RCD protected, so I would say OK.

 

[ianphilip007]

true lol the lights would go out in a power cut and so would everything else. dont think they have regulated the almighty yet but give them time

 

[pencilpusher]

Reg. 314 states that it must not cause danger if a fault occurs on one circuit? With a standard non time delayed RCD main switch surely this would cause the whole house to black out if a single fault occurs on any circuit?

Yes but it also states you need 30ma RCD protection and by removing that you are leaving it in a "worse" state than when you arrived.

 

[ianphilip007]

exactly how i see it ipf exisiting installation designed/installed to earlier regs

 

[telectrix]

perfectly acceptable to add your new circuit. fill in a EIC. just comment on the fact that the CU does not comply with current regs. on to next job.

 

[Guitarist]

Agree with tel...

 

[Des 56]

Change a board,danger,warnings ?

Is this a consumer unit that is a melting catastrophe about to happen ?

No, its a unit with a front end rcd,as fitted in millions of homes, including mine, and doing on the whole as fine a job as any cheap and nasty and new twin rcd up to date unit which could be argued is itself a compromise of the intention of the regs itself

There is very little problem, other than slightly more inconveniance than your new units on the perhaps extreemly rare occasions when faults present themselves

I find some of the comments, about changing boards and danger etc on this matter,a little disconcerting

We are told in many posts on this forum, about the perception that the public see themselves as being ripped off when we mention the need for earthing and bonding to do small jobs
That perception may have some justification,with changing consumer units because there is a front end rcd and warning the customer of the imminent danger they are in,unbelievable

 

[Deleted member 26818]

A bit of a dilema really.
The existing installation doesn't meet the requirements of Section 314, and neither will the new circuit.

 

[DNS1]

perfectly acceptable to add your new circuit. fill in a EIC. just comment on the fact that the CU does not comply with current regs. on to next job.

That's how I understand it.

RCD on the incomer is perfectly ok, if not ideal. Surely just a case of note it as out of date (16th Ed?) and carry on.

My folks have one of these in their place (installed in about 1995), inconvenient but not dangerous (especially the day muggins here thought he'd test the RCD trip function of his shiny new Metrel on a ring circuit, without realising it would take out lights to the whole house!). Got to be safer than the non-RCD board installed in my flat 5 years previously.

 

[DNS1]

That perception may have some justification,with changing consumer units because there is a front end rcd and warning the customer of the imminent danger they are in,unbelievable

Very true.

My folks recently had a guy (ok, admittedly he was a part p kitchen fitter) tell them that they'd need a new DB because the 40A cooker circuit couldn't handle a double oven and induction hob (he couldn't do diversity calcs either, but that's another story) and that there was no room available for an extra dedicated hob circuit.

Didn't bother to look properly and see that one of the ways was taken up by a disconnected MCB for a bell transformer and instead decided to try to flog my mum a new DB...

 

[ianphilip007]

A bit of a dilema really.
The existing installation doesn't meet the requirements of Section 314, and neither will the new circuit.

Firstly the existing installation does not have to meet the requirements of 314.1 as it was designed/installed to an earlier edition of the regs and the current regs are not retrospective. Why will the new circuit not comply with current regs ?

 

[Snapester]

Nobody mentioned changing the board, i was just stating that a front end RCD is not a great idea.

 

[telectrix]

IMO, the new circuit will comply with current regs., but the installation as a whole does not. i'd be more concerned about ensuring that earthing and bonding were compliant.

 

[ianphilip007]

i agree tel re bonding and earthing and as long as the new circuit complies to current regs thats the important part. short of fitting a new board which is not always needed or practicle cost wise. in my opinion the existing installation predates 314.1 so a note on the cert stating the deviation will suffice

 

[Deleted member 26818]

Firstly the existing installation does not have to meet the requirements of 314.1 as it was designed/installed to an earlier edition of the regs and the current regs are not retrospective. Why will the new circuit not comply with current regs ?

Yes I agree, the Regulations are not retrospective.
However as to whether the installation complied with the requirements of the Regulations current at the time of construction, is arguable.
It's been a requirement for installations to be divided into separate circuits for to my knowledge just over 45 years (the 14th edition was introduced in 1966).
The requirements of 314.1(i) & (ii) in the 17th edition, are exactly the sames as were in the 16th edition which was introduced in 1991.
I couldn't tell you the exact wording used in the 15th edition.
I'll leave it to you to decide whether a fault on one circuit affecting every other circuit in an installation, avoids danger, minimises inconvenience or complies with the requirement to keep circuits electrically separate.

 

[ianphilip007]

Yes I agree, the Regulations are not retrospective.
However as to whether the installation complied with the requirements of the Regulations current at the time of construction, is arguable.
It's been a requirement for installations to be divided into separate circuits for to my knowledge just over 45 years (the 14th edition was introduced in 1966).
The requirements of 314.1(i) & (ii) in the 17th edition, are exactly the sames as were in the 16th edition which was introduced in 1991.
I couldn't tell you the exact wording used in the 15th edition.
I'll leave it to you to decide whether a fault on one circuit affecting every other circuit in an installation, avoids danger, minimises inconvenience or complies with the requirement to keep circuits electrically separate.

no it doesnt meet 314.1 i totally agree thats why i would note it as a deviation on the cert otherwise the only option on these older boards would be to replace the cu as parts to reconfigure are just not available and often that would not be economically viable or really nessacary. if your statement about weather the installation ever complied with the regs of previous days is true then surely these boards would have been removed as there must be millions of them. in my opinion as long as the main earth,main bonding and diconnection times are met for the new circuit and the existing rcd operates correctly the only issue is inconveiniance. unfortunately this cannot be avoided so a note on the cert stating that the CU does not meet (314.1 BS7671) should suffice.

314.1 will never be met with a CU with a front end rcd, but in my opinion it is not dangerous and is only slightly worse than a new dual rcd board. only danger comes from inconvieniance and as has been suggested EM lighting near CU sounds like a goos idea.