Hi Integrity CU

[Newpark7]

Hi all

I am fitting a new Crabtree High Integrity CU tomorrow at customers premises, as it is all solid floors DS & chipboard US with glued downcarpets. I am proposing to use the redundant cooker cable (gas cooker now fitted) as a feed sub main circuit to supply the integral garage via 32A CB.

I was thinking of using a 3 way garage CU in the garage to feed the garage elecs and use the 3rd way to provide a feed to a WP JB and SWA to the shed.

How do I provide discrimination as all three CU's have 30ma RCD's the HI CU does not have any non RCD spare ways and in any case as I am using the existing cooker circuit which is buried in the wall I will need RCD protection for that part of the sub main.

Any suggestions on the discrimination side or is there a better way of doing things without taking half the house to pieces?

Cheers

Mark

 

[Spudnik]

The house end RCD will be fine.

Just use a main switch in the other CU's.

 

[baldsparkies]

As Jason said, or use an rcbo in one of the unprotected ways of your high integ board. Bit more expensive though (Around £25-00 for the rcbo)

 

[tuckermot]

are you saying that the rcd in db1 will protect the submain to db2 and db3 hence you can put db2 and db3 circuits on non rcd boards just asking as i had this problem and that is what i did as i could not acheive discrimination and the most sensitive rcd in db1 was allways knocked out 1st even if the fault was in bd3 !!
thanks
Rich

 

[baldsparkies]

If your submain is protected by an rcd from main board ie DB1 then the board that submain supplys will only need a mainswitch and mcb combination. A new high integ board has dual RCDs so one submain could be fed from the first rcd with the second submain from the 2nd rcd. Alternatively, seeing as its a high integ board you could use an rcbo which would give the submains dedicated protection, but at extra cost.