Part P - how far to go?

[Alexander Lamaison]

How far do you have to go to be compliant with Part P when working with an existing installation?

You are't required to bring existing work up to standard of the current regs, right? The rule-of thumb (sorry, historically) is that you should leave the installation no less safe than you found it.

But, I'm told work cannot be completed if the bonding is not up to scratch. How can these two things both be true, as, if the bonding was not there before you started and is not there afterwards, you've not left it less safe than before, have you?

What other things must be as per the latest regs before you can complete any work?

For instance, if I add a socket to an existing bedroom circuit, must I add an RCD?

Alex

[A.Lee]

Well, not really true.

Bonding and earthing has to be up to current regs. That'll, generally, be a 10mm cable to water and gas, and a 16mm for the earthing conductor. Slightly different for TT systems, and, earthing conductors if you use the adiabatic equation to calculate the size.

If the cables are more than 50mm below the surface, or, surface mounted, and the socket cannot be used for outside equipment, then you can just add another socket onto an existing circuit.

Buried at less than 50mm, or, available for outside use, or in a special location, then the cables should be 30mA RCD protected.

[ARW]

That would depend on what work you are doing. The bonding would not need to be upgraded to swap a light fitting etc but you could not install a new cooker circuit without upgrading the bonding.

Possibly the installation of supplementary bonding in a bathroom or changing all the circuits in there to RCD protected circuits (depends on what you are doing in the bathroom)

The 17th edition does makes RCD protection of nearly all sockets mandatory. So the new socket would need RCD protection. The cable supplying the new socket may also need RCD protection

gives the rules on where the cables need RCD protection.

[Alexander Lamaison]

Which raises two more questions:

1) A new CU would be protected by more than one RCD so as to minimise the effects of a nuisance trip. Does this apply to an existing installation and prevent me installing a single RCD before the CU to cover all the sockets? (the CU doesn't cover the lights) 2) Would installing such an RCD count as altering or extending the circuit and therefore make it notifiable?

Alex

[ARW]

314 applies. I would say it is as acceptable as the 16th edition regs that used to do just the same thing.

Dunno - but I would say probably. But then I would say nothing if it was a DIY job. I have a few RCD main switches knocking around if you need one.

There is nothing stating that the RCD protection for the new socket (that is the only one that would require RCD protection) has to be in or before the CU.

[John Rumm]

Yup that is still basically as true as it ever was... (i.e. only kind of)

Checking that the main equipotential bonding needs to be to current standards is a requirement for carrying out any work.

Instating (or rectifying any deficiencies) in it are not in themselves notifiable either.

It was certainly the case that altering a socket circuit that did not have a RCD would require it to be protected by an RCD (not a bad idea anyway in the general scheme of things).

However I have a feeling that amendment 1 to the 17th edition contains some changes to allow you to skip this in some circumstances. Alas I don't have the text to hand...

[ARW]

ISTR that was in the proposals but not in the ammendment.

[ARW]

Are you sure about that Alan?

I still believe Q1 and Q3 apply to the current regulations.

I am sure the OP will like the link.

And of course I might ignore the rules and not bother with the RCD depending on the customer.

[A.Lee]

After reading 411.3.3, I'm probably wrong. I was under the assumption that a non-rcd'd existing circuit can have socket outlets added on to it without rcd protection, unless in a special location, or for outside use. So yes, new socket outlets on any domestic installation will probably need rcd protection (except for some exclusions, generally not applicable to 'normal' users). Of course, the cables should still be below 50mm, or surface mount, or the cable will need RCD protection, which is probably why I was wrong - thinking of the cable protection.

Ta Alan.

[John Rumm]

That may well be the case, since I can't find any reference to it...

[Alexander Lamaison]

That answers about a bazillion questions that had been bugging me!

Alex

[dennis]

A 2.1..

The desired outcome is that the circuit should be protected by an RCD. Fitting an RCD socket doesn't protect the circuit.

[ARW]

Who said it does?

[Andrew Gabriel]

This depends on the BCO (if you are DIY'ing it). Some are quite happy for small changes to a 16th Ed installation to still conform to 16th and not 17th Ed regs, bacause of the significant incompatibility between the two when working on an existing installation. Check first though.

[Alexander Lamaison]

Assuming I stick to non-notifyable work, the BCO wouldn't even come into it. But if BCOs are happy with this, does it mean it's compatible with the requirements of the building regulations?

Alex