Power to external office

[DeanAlani]

Hi

I've now had a quote and just would like some opinion on this. Its not that I don't trust the proposal. Just after some thoughts.

We have an existing 2.5mm swa cable going to our outside office, the proposal is to feed of a 32amp RCBO in the consumer unit in the house (its an RCBO board) with a 2.5mm swa cable and connect this to the existing 2.5mm swa outside so its new circuit from the board, then feed this is into a non RCD rated consumer unit, as the circuit is being fed from is an RCBO so the office CU will be a standard100amp main switch CU with a breaker for sockets and a breaker for lights in the outside office.

Does this sound ok?
Thanks

 

[Spoon]

There be 2 x 2.5kw radiators

Any chance of reducing this?

 

[DeanAlani]

Any chance of reducing this?

Its actually 2kw oil filled radiators literally what it says on the radiator

 

[Spoon]

Its actually 2kw oil filled radiators literally what it says on the radiator

Well, that is better.

 

[pc1966]

Tally up what you really want in the office before deciding.

2.5mm should be on a 25A RCBO at most (subject to voltage drop depending on the length) so you have enough for lights (probably 1A max) and around 5.5kW of other stuff. Electronics (TV/PC/etc) has a high in-rush when switched on so if you have 500W expected then treat it like 1-2kW just in case.

So for a basic office with 3kW heater, several LED lights and a few IT things it would be OK. But not on 32A!

However, the extra cost of going for 4mm SWA, or even up to 10mm, is not much compared to the overall installation and it would give you easy/cheap options in the future if you found you needed more stuff out there for any reason.