Moving a CU & the electrician says it has to be replaced

[leathtj]

The current CU is a split load unit thats 15 years old and works perfectly. A year ago I had a new bathroom and the sparky passed the rewiring without any problems

Now I am doing a new kitchen extension and need to move the CU. The builder's sparky says the CU has to be replaced with a unit that protects all circuits. I have no way of knowing if this is true or false. All I know is that a lot of money has been added to the quote

How can I confirm my old unit is no longer good enough to pass inspection.

Any help gratefully received

 

[ColJack]

without seeing it we can't say for sure..
however, new regulations require that all circuits that have cables burried in a wall less than 50mm deep require RCD protection.
another reg says that we can't have just one RCD to protect the whole installation, so the option is a CU that has 2 or more RCD's, or a CU that has one RCD and a series of RCBO's.. , or a CU that has all RCBO's..

seeing as the sparky becomes responsible for the entire installation when you move a CU due to the need to re-terminats / extend all the wiring in it, then it has to be brought up to the current standards..

 

[sparkyspike]

You only have to worry about NEW circuits. If you are just installing new lighting, sockets and cooker circuits, then you can fit individual RCD breakers (called RCBOs) in the consumer unit . This will avoid fitting a new CU, but only if the existing one is compatible with RCBOs.

If you are just installing one or two new circuits then this may be the way to go. But RCBOs are (relatively) expensive and it can sometimes be cheaper to fit a new split load board. The advantage of this is that you can then protect previously unprotected circuits which is a good thing to do.

On the other hand, RCBOs provide a much better installation as individual circuits will be interrupted due to a fault rather than half of the installation.

You have the choice - fit RCBOs for the new circuits, OR fit a dual RCD split load board, OR fit a combination RCBO/RCD board, OR fit a CU with 100% RCBOs.

My personal choice is to use a single RCD split load board with a few non essential circuits on the RCD side and dedicated RCBOs on the non-RCD side.

Ask your electrician about all these options and get a price for them.

 

[sparkyspike]

The builder's sparky says the CU has to be replaced with a unit that protects all circuits.

Probably not the case. Only new circuits relevant to the work being carried out require protection. To protect other circuits is a good thing to do, but not required in most cases.

 

[JohnD]

a lot of money has been added to the quote

how much?

what did the spec originally say was the electrical work to be done around the CU, and what does the new one say?

 

[ColJack]

as it's being moved anyway then the work is the same, still have to re-terminate all the wires so the additional cost would only be for the unit itself.. between £100-£200 depending on the spec..

 

[sparkyspike]

as it's being moved anyway then the work is the same

Sorry I missed that bit. Forget what I said about only new circuits needing RCD protection . As CJ says, a new CU has to be installed to up-to-date standards.

 

[leathtj]

thanks to all. I can make some sense of the situation based on the above.

 

[JohnD]

If you are spending a lot of money you might consider having an RCBO on each circuit. This is the most expensive, but also the finest, solution (provided it is a good brand) as it gives every circuit its own RCD combined with its MCB but does not need a larger enclosure.

 

[Lectrician]

MEM have developed a new consumer unit with greater head room to allow for RCBO's. It is designed to be fully loaded with RCBO's. The CU has the same foot print, but the top earth bar etc has been turned and moved to one side, with a neutral bar on the other side for the RCBO tails.

They have also finally released their domestic RCBO for the domestic boards (they have been selling the commercial RCBO's under a different part number for the last year or so).

 

[aptsys]

If you are spending a lot of money you might consider having an RCBO on each circuit. This is the most expensive, but also the finest, solution

I think I would agree if the RCBO could indicate the cause of it tripping. But they are a PITA with intermittent faults.

 

[JohnD]

they are a PITA with intermittent faults.

Unlike an RCD feeding several circuits?