Implications of having CU replaced?

[bremen1874]

My last daft question for a while…

After reading this forum for a while with regard to the wiring I’m going to need in my kitchen I’m now considering having my CU replaced as part of the same job.

It’s currently an eighties vintage Crabtree unit with big brown breakers. The existing circuits are cooker (30A), ring (30A), upstairs lights (5A), downstairs lights (5A), immersion (15A) and one spare. There’s also a small much more modern CU alongside containing a 40A MCB and a 63A 30mA RCD that supplies the shower. There’s a sticker on the main CU stating that it’s connected to a Protective Multiple Earth system.

The CU is basically pig ugly and is located in my hallway with no good way of hiding it. It also doesn’t appear to have any provision for adding RCD protection to any of the circuits which I’d prefer. Finally at some point I’d like to get mains out to my shed and have something more substantial than the existing single socket spur in the attached garage.

Is it likely that the CU can simply be replaced, or is there going to be a lot of other remedial work required? I know that without actually inspecting the wiring a simple yes or no answer won’t be possible but I’d appreciate any insight into the likely problems.

Due to a lack of planning on my part (and knowledge about part p) everything is on stop until I can get an electrician on site. I need something to do in the meantime even if it's just looking for potential problems.

Thanks.

 

[Mark1972]

If the installation hasn't been modified, the chances are a straight swap will be on the cards - though bonding in your bathroom will probably need doing.

Like you say - very hard to advise without seeing it or, more importantly, testing it.

 

[Adam_151]

Probably C50 range then (not to be confused with a C curve 50A MCB )

Should hopefully be straightforward as the other poster says unless bodgit and scarper have been in (and assuming install is the same vintage as CU)


It'll ovbiously need every circuit testing, and issues that may need remedial work are likely to include:

Undersized main bonds
Lack of bathroom sup bonding
Undersized ring final circuit CPCs (if pre '83) - should just need a calc to prove
And possibly too few circuits and outlets for modern high-tech life (for example one ring final circuit for entire house)
and of course, lack of RCD protetcion, but as we are talking about a CU change here, that'll be dealt with anyway

 

[oohthatslive!!]

just out of interest, are you required to upgrade the
supplementary bonding to the bathroom if you change the CU ,
or is it something that is advisable?

 

[CallEdsFirst]

Probably C50 range then (not to be confused with a C curve 50A MCB )

Are you copying me?

The breakers sound like Crabtree C50, which are becoming increasingly difficult to source now. Slightly different from Type C breakers which would be worrying if it were the case!

I said it first so there! Bremen, have you been caught double banking?

 

[DESL]

just out of interest, are you required to upgrade the
supplementary bonding to the bathroom if you change the CU ,
or is it something that is advisable?

It's a requirement when making a major alteration to an installation i.e. CU change, that the whole installation should be brought up to date

 

[oohthatslive!!]

just that on a recent job that i was on , the spark changed the
CU and he did test all the circuits but didnt upgrade the
bonding in the bathroom. All the time whingeing about
5 day wonders whilst he did his work. Said something about a
4 year apprenticeship. Just goes to show doesn't it.

 

[oohthatslive!!]

just that on a recent job that i was on , the spark changed the
CU and he did test all the circuits but didnt upgrade the
bonding in the bathroom. All the time whingeing about
5 day wonders whilst he did his work. Said something about a
4 year apprenticeship. Just goes to show doesn't it.

 

[equitum]

just out of interest, are you required to upgrade the
supplementary bonding to the bathroom if you change the CU ,
or is it something that is advisable?

It's a requirement when making a major alteration to an installation i.e. CU change, that the whole installation should be brought up to date

Absolutely not the case i.e. a requirement. The installation should be no less safe than before the replacement commenced. As a minimum earthing and bonding (i.e. main bonding) need to be adequate.

For example, it is permisable to replace a consumer unit where no cpc exits to the lighting circuit, providing risk assessments/precautions/warning notices etc are undertaken.

Edit: p.s. I'm a 5 day wonder.

Edit: pps. But it is advisable, as it is an additional (to EEBADS) form of protection against indirect contact.