Domestic: 20A DP switches and ring final circuits??

[8yf13l0]

Hi all .

Seeing alot of cases where I have seen 20A DP switches in a kitchen (for example) each feeding a radial 2.5t&e to each white goods appilance or similar, and the 20A DP switch primarys are fed from the 32A kitchen ring final circuits - Is this accepteble to BS7671?

I'm guessing if it's only serving a 1 gang s/o or 13A fused spur it would not be at risk of overload at the switch?

Please advise.

Many Regards

Jamie

 

[Dave OCD]

OK, so we have a 20A DP control switch with its supply side as a point in an RFC protected at 32A. The load side connects to some accessory, either a single socket outlet or FCU, that will limit the load to 13A by way of the BS1362 fuse. We declare it as a fixed load so the 20A switch is within its thermal (continuous load) rating.

But what happens with a short circuit on the unfused spur? The 20A switch has to survive the fault being cleared by a 32A device without disintegrating, instead of a 20A device. Any accessory intended for use on an RFC will have been designed for that duty, but has the 20A switch? Check with manufacturers? Splitting hairs? Take it one stage further - given suitable cable would it be acceptable to control a 1A fixed load on a 40A circuit, using a bog standard 5AX light switch?

Discuss...

No because you'd never get the incoming 40a rated cable into the switch terminal.

 

[Dave OCD]

the light will go out.

Or stay on when the contacts have fused together.:smilewinkgrin:

 

[Lucien Nunes]

you'd never get the incoming 40a rated cable into the switch terminal.

I chose 40A for this very reason - Bare 2H2.5 MI will do 40A and will fit any decent light switch terminal. Anyway, does the cable need to be rated for 40A inside a panel and carrying a fixed load of 1A?

 

[Dave OCD]

Well let's say a 1mm cable was connected to the outgoing side of this switch feeding a 1 amp load, if there was a short in this section of the circuit the 40a MCB would still disconnect before any other damage was sustained ?

 

[rustynails]

I've done this sort of setup before but always put the fuse module before the dp switch