Minor works certificate and testing questions

Quite a few questions there!

1 No you are responsible only for the new bit, but the whole circuit to the new bit needs to be considered.

2 You need to be satisfied that all the upstream parts of the installation are compliant.

3 If RCD protection is required, you need to fit it, but SRCDs are no longer compliant - search for various threads on that subject. I do not think that you need to concern yourself with main bonding, etc. That said, there is nothing to stop you advising the client and agreeing to further work.

4 No, I think that you just need to consider the new bit.

A range of opinions may emerge!

641.5 For an addition or alteration to an existing installation, it shall be verified that the addition or alteration complies with the Regulations and does not impair the safety of the existing installation.

644.1.2 For an addition and/or alteration to an existing installation, any defect or omission that will affect the safety of the addition or alteration that is revealed during inspection and testing shall be corrected before the Certificate is issued.

So, when modifying, (i) you shouldn't make the existing stuff worse. This implies you do suitable T&I on any existing parts that may have been affected by the modification. (ii) the new bits should comply with the current regs: so when adding a socket, the new socket must be RCD protected, but you're under no obligation to RCD protect the old sockets on that circuit. (Of course it may be easiest to add RCD protection at the origin of the circuit anyway.)

I would argue that you have a duty to ensure that the new work is safe and compliant, and that this means a certain amount of inspection and testing of the existing work.

As extreme cases consider the following. If an existing circuit has no effective earth, then a socket outlet added thereto can not be safe, no matter how well the new work is done.

Or if an existing 20 amp circuit is wired in 1.5mm twin with earth, then an addition thereto is most unlikely to be safe*.

I would however be a LITTLE more relaxed about MINOR deviations in the existing work that do not significantly affect the safety of the new addition.

For example if existing socket outlets have no grommets on cable entries, I would probably consider it acceptable to extend the circuit if otherwise OK.

Likewise if the existing work is in some non standard colour code, I would in the old days have extended it in red/black and these days in brown/blue, despite the existing work never having been compliant.

In some districts there is a lot of twin with earth cable with black and white cores, this I would extend if otherwise OK, double checking polarity and sleeving the old work with the new colours at the junction, but not throughout. Three core SWA with odd colours likewise.

*For a bonus point, suggest a circumstance in which this could have been safe, and still safe despite being added to.

broadgage: 
 

I would argue that you have a duty to ensure that the new work is safe and compliant, and that this means a certain amount of inspection and testing of the existing work.

As extreme cases consider the following. If an existing circuit has no effective earth, then a socket outlet added thereto can not be safe, no matter how well the new work is done.

Or if an existing 20 amp circuit is wired in 1.5mm twin with earth, then an addition thereto is most unlikely to be safe*.

I would however be a LITTLE more relaxed about MINOR deviations in the existing work that do not significantly affect the safety of the new addition.

For example if existing socket outlets have no grommets on cable entries, I would probably consider it acceptable to extend the circuit if otherwise OK.

Likewise if the existing work is in some non standard colour code, I would in the old days have extended it in red/black and these days in brown/blue, despite the existing work never having been compliant.

In some districts there is a lot of twin with earth cable with black and white cores, this I would extend if otherwise OK, double checking polarity and sleeving the old work with the new colours at the junction, but not throughout. Three core SWA with odd colours likewise.

*For a bonus point, suggest a circumstance in which this could have been safe, and still safe despite being added to.

OK thanks.

Ref method C? 20A CCC.

The example that I was considering, was a 20 amp circuit in 1.5mm twin with earth that supplies only a cold room refrigeration compressor, rated running current 9.5 amps and protected by a thermal overload relay set at 10 amps.  20 amp fuse was only for short circuit protection.

Safe and still safe safe after I added a 3 amp fused connection unit for a data logger, with a negligible running current, less than 0.1 amp.

Obviously if the MEIWC does not contain all the details you need to record, then you may use an EIC for minor works if you wish or record them on an attached piece of paper.

I suppose if the MEIWC does not contain all details needed then what you are doing is presumably not minor works