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

 

[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 Surely just a case of note it as out of date (16th Ed?)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.