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Generator and none rcd submain dilemma

hertzal123

Hi,a customer as asked me to enable him to connect a temp generator to his house.There are 2 cu,s,both dual rcd,but one is fed by a t and e buried in plaster from a a BS88 switched fuse.The

customer will not replace the submain with swa.My dilemma is,do I fit a type S 100ma rcd for the submain,or leave as is.Both would be recorded as a deviation.There is a hot tub fed from the sub main.

The generator neutral will be earthed and spiked.

                                                                                                               Thanks for any advice,

                                                                                                                          Regards,Hz

  • 0

    I don't see an issue with the sub mains being buried in plaster - they're existing not anything you'll have to certify.

    You'll likely need an RCD straight after the generator to provide ADS anyway - that should cover the submains at least as far as ADS is concerned, you could even make it a 30mA one and provide additional protection as well.

       - Andy.

  • 0

    Unless the genset is very big it will not blow the BS88 anyway, but the volts will fall away or it will stall instead. An RCD at the genset end of things, just after neutral and CPC go their separate ways, is probably required, to replace that missing ADS - though as you suggest a delay type will be much less of a pain and discriminate with the rest of the set-up. Do keep your wits about you to be sure that you are not relying on company earth as the only earth at any time the supply may be off,  and that the DNO N-E link does not appear as a fault that will trip your genset RCD - this usually involves a ganged  changeover to remove all poles of the DNO supply when genset is running, assuming you are not trying to do synchronous running in parallel with the street mains. If you are come back, that is harder.

    I'd not blink about the T& E sub-main, for sure you'd prefer armour. and fit that if it was a new job today, but it is already there, and so long as the route is known, it is not going to suddenly become more of a problem in terms of nailing into it when a genset is added.

    Mike.

  • 0 in reply to mapj1

    Thanks for the replies,Mike and Andy.

                                      Regards,

                                             Hz

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