CU & Submain

[RichA]

I am refurb’ing my utility room and would like to move the CU so it is in a cupboard.

The new CU would be c2.5m from the current CU, and similar distance from the meter which is close to current CU (on outside wall).

How far can the CU be from the meter before a submain is required?

What (approx) would a submain cost?

 

[ban-all-sheds]

I am refurb’ing my utility room and would like to move the CU

Which one?

How far can the CU be from the meter before a submain is required?

Is there a good reason why you can't ask your electrician?

What (approx) would a submain cost?

Whatever your electrician says it will cost.


The supply to your CU is the least of your problems - what about all the final circuits from it?

And what are you doing to be doing about Building Regulations approval?

 

[RichA]

I am refurb’ing my utility room and would like to move the CU

Which one?

How far can the CU be from the meter before a submain is required?

Is there a good reason why you can't ask your electrician?

What (approx) would a submain cost?

Whatever your electrician says it will cost.


The supply to your CU is the least of your problems - what about all the final circuits from it?

And what are you doing to be doing about Building Regulations approval?

Thanks.

I only have 1x utility room (and 1x CU).

The plans have the new CU in the cupboard (out of shot to left in photo). But the architect annotated the meter in the same cupboard. However it is on the outside wall.

The main contractor has suggested there will be a variation to instal a submain, due to location of meter.

I am looking for options to consider to potentially avoid additional cost.

Contractors electrician will be doing all work, including final circuits and BR approval.

 

[ban-all-sheds]

I only have .. 1x CU).

But the architect annotated the meter in the same cupboard. However it is on the outside wall.

That's architects for you.

Contractors electrician will be doing all work, including final circuits and BR approval.

Then he has to be the one responsible for all aspects of moving the CU, including any necessary design and installation of special provisions because of the length of the meter tails.

You can't do any of it, so you have to leave it to them.

If you have a contractor who you cannot trust to give you good advice and to not carry out unnecessary work then the sooner you get rid of him the better.

 

[RichA]

For the avoidance of doubt I won''t be doing any work on this myself.

The upper CPU is my old CPU, the lower one belongs to the builder for his temporary supply.

I trust the contractor to do a good job, I just don't fully trust him to consider the cheapest solution. I like to go into a discussion armed with a few options.

 

[AndyPRK]

As long as cu within 3m of meter it should be fine.

The issue is all the outgoing cables need moving.

 

[John D v2.0]

As long as cu within 3m of meter it should be fine.

The issue is all the outgoing cables need moving.

Agree. even if you need over 3m cable length it's not hard to deal with.
what the builder calls a submain would just be an isolator or switchfuse (to keep the DNO happy) close to the meter, and then some armored cable buried in the wall to the CU.

 

[RichA]

This is my meter. Are you allowed to put the Submain in here, or do you typically mount inside the house?



Is something like this what would be required?



The house is being rewired so outgoing cables are being moved in anycase.

 

[John D v2.0]

Yes you can put it there, in fact the bottom right rectangle is for an isolator.
Technically it should be the metering company's isolator, but i don't think you'd get in big trouble for it.

 

[ban-all-sheds]

Really, only the DNO can give you a definitive answer about whether you need your own fuse in the outgoing tails. There's a widely accepted rule of thumb that at over 3m one is required, but I don't think that that is formally declared anywhere. Concealment of the tails is another trigger.

The underlying issue is that the longer the tails are, or the more hidden they are, the more they are likely to get damaged, and therefore the greater the risk that the DNO owned fuse in the cutout will rupture. They don't want that - they would prefer a fuse which the customer has to replace.

If the length is/will be under 3m then the ROT says you don't need your own fuse.

Common sense though says that if you run the tails through a ragged hole in a wall you might like the idea of a fuse, but protecting the tails against mechanical damage in the first place would be better than measures to deal with the effects of damage. An isolation facility will also be useful for your electrician when he is moving the CU.