Garage supply

7 Jun 2008
Reaction score
United Kingdom
I have recently moved into a new property and noticed that the garage supply cable from the main house CU was wired in 1.5mm SWA current carrying capacity of 21A protected at the Main CU via a 20A circuit breaker.

The garage mini-CU has a 80A main switch with 30mA rcd and serves 1 x 6A MCB lighting CCT and a 32A MCB socket CCT.

I am thinking that there is an issue with discrimination , there are a couple of ways around it that i can think of.

What are you thoughts on this, i know ideally i may have to upgrade the supply cable to the garage CU at some point for furthur expansion.

1. reduce the size of the 32A socket MCB to 16A.

2. Maybe fit an RCBO at the house CU, allowing removal of the 80A RCCB in the min-cu.

your thoughts please.


Sponsored Links
Personally I would just leave it. Even if you reduce the breaker to 16A you still won't gaurantee discrimination and you will have just added a pointless lower limit on the ammount of power you can use out there. There is no problem with having the RCD protection at the outbuilding end indeed many consider this the preffered configuration.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links