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I have a 1946-built semidetached house in the UK, which has a standard 10-way consumer unit installed. Now, after having a new extension built, I need to replace it with another CU (10-way isn't enough any more; plus the old one doesn't satisfy changed regulations). I'm confident enough to do the job - and then have it inspected by the qualified electrician. Yet, for obvious reasons, I need to cut off power supply to the CU.

The picture below shows the entry point. The large red/black wires at the top are the ones going to the meter - and then from there to the CU. Is there anything on this entry point that I can use to cut off power supply? Or do I need to contact the power company?

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That is the supply fuse you cannot touch that. It is under the control of the Distribution Network Operator (DNO). It is a legal offence to touch it and it will have steel twist tags on it that have a stamped number on it which is recorded with the DNO so they know if it has been tampered. However after it should be the supply meters and then it should go to an isolator. You are supposed to turn off the isolators and and you can modify the installation after that point. However changing a CU is notifiable work in the U.K it is not something you are supposed to do yourself without being a competent Electrician.

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    Thanks. There's no twist tags or any stamped number. Unfortunately, there's also no isolator of any kind between the meeter and the CU - so I may have to get the utility company to cut off the supply temporarily - to install an isolator switch between the meter and the CU. As for the changing the CU, I'm competent to do it - but I'm not officially qualified, hence need to have the work inspected afterwards. I have discussed this with the building inspector covering the extension work - and he's happy with that approach. – Aleks G Feb 19 '18 at 18:09
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Ask your utility nicely

You'll need to ask your utility to cut the power service to the building temporarily. They should be able to do it free of charge, or at worst for a nominal call-out fee if they have to physically mess with things at your location (many smart meters can remotely cut power).

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Call the utility and ask them to temporary cut your power.
I suggest you also to add a main (and big) breaker just after the meter, so if in future you'll need to do something in the breaker-box you'll simply have to flip a switch and not to call your utility. Suggest to put a switch big enough (as big as the max power carried by the new panel).

  • A switch between meter and the new CU sounds like a good idea. It'll need to be 100A. – Aleks G Feb 19 '18 at 14:19
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    EU+UK installations typically have a main breaker which is an RCD (GFCI) however at a higher trip current (30ma). (8ma is better to protect occupants from shock/drowning/falling, but that is too sensitive for a whole house. Hence the US approach of 8ma GFCIs per circuit). However that RCD is typically inside the consumer unit. – Harper Feb 19 '18 at 18:08

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