rcd prob

[wattsup]

Mmm, I think this is why the red tape is strangling the industry. For instance it could be said an outside light need not be protected by an rcd/rcbo etc. Yet if read at a different angle it should be protected?
Likewise anyone can plug the lawn mower into a front room socket, not protected. Cut the lawn back garden, into kitchen socket it must be protected.
Anyhow thats by the by.

I agree entirely, the gen feed should be wired according to normal rules regards cable size and a suitable overcurrent device. But the key points of regs argue temp or otherwise should be treated the same.

In actual fact I can't see any other way but to swap the rcd for a normal 40a dp isolator with a 32a breaker fitted feeding the transfer switch. All wired in 10mm 3-core swa...thats how its wired at the moment.

The transfer switch is rated 100amp so mains are as normal, 25mm tails

 

[uksel]

if you're going to be supplying the domestic consumer unit then i would probably suggest going a lot bigger than a 32A breaker. i would imagine either the same size as the breaker in the CU or larger. perhaps put a 80A DP breaker at the consumer unit and a 100A DP breaker in the one way consumer unit?

if it's wired the way i am assuming it is anyway...

 

[wattsup]

That is not practical nor makes sense, the gen can supply 40 amps max, if I allow 100 amps the gen will go into melt down. Also the cable supply from the set would need to be able to cope with 100 amps, so would the breaker. So I would need a min 16mm from the set. The set cannot supply 100 amps, so the breaking point is 35amps or thereabouts. A 32 amp breaker will protect the cable (10mm) and the generator.

Maybe I ain't been clear, or perhaps the understanding of the changeover switch is not clear. This is a backup genset with limited output (emergency use only)

The changeover switch can handle 100 amps, but it needs to, because 90% of the time it controls mains utility input

It would be very unwise and make no economical sense to oversize cables and breaker from the gen supply.

The 32 amp breaker will trip if prolonged @ 40 amps, just what I want.

 

[uksel]

you don't remember you mentioning the max current output of the set > neither it's intention for only a limited supply backup

if your set is connected directly to the main breaker of the CU when in use and there is plenty going on in the installation ie. over 40A which is easily do-able, then the genny breaker is going to trip straight away is it not?? or is it not an instantaneous switchover?

sorry if some of this seems remedial to you, but it's hard to picture what's happening without seeing it infront of me...

 

[wattsup]

Yes if over 40 amp on changeover the gen feed will trip (i hope)
However the customer will be aware when on gen feed, and realise load needs to be reduced, then flick the gen breaker back on..I thought I mentioned earlier 19kva..it is unlikely however, average load at peak times is 30amps. Most times much lower.

No, not instantious in the true sense, most generators will not give instant backup (unless spending £££££££££££££££, the set stablizes before it provides power, if acceptable the feed will energise...normally a 20/30 second delay