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Electrical

Domestic 3-phase upgrade

Anonymous user 22/10/2026 - 7.59 AM

I've booked a heat pump install for the new year, and part of that requires a cut-out upgrade. It's got me thinking about upgrading the 3-phase, as my next car will be an EV, I'll want to replace gas oven/hob, and maybe solar later. The problem is my meter and CU are in the middle of the kitchen, and National Grid say any new connection would only go as far as an external cab. Also, the current CU is jammed in tight between the ceiling and the meter, and all 3-phase CUs seem to be much bigger. Could I use the existing CU with just one phase as an interim solution?

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1 Answer

ST Electrical

Rating: 5 out of 5

Bracknell

A three phase cut out is essentially exactly the same as a normal supply just with two extra fuses So essentially you can just put the live meter tail from your existing fuseboard into L1 and neutral and earth as normal. I will also say that your house uses a lot less power than you think, so an upgrade in fuse size on a single phase cut out will suffice in larger houses. This is usually for commercial properties or plant machinery. Car chargers use dynamic load management to ensure they are never going to blow your fuse. So you could have a 100a single phase cutout with a car charger installed, you could a have induction hob and heat pump on, aswell as everything on but when you turn the charger on it may run at half speed untill you turn other appliances off Look up “diversity” on electrical systems Additionally they do 3 phase boards that are the same size as single phase, with staggered bus bars that allow circuits to go in horizontally

Answered22 October 2026