Just installed a 15KVA single phase standby genset into a domestic property last week with manual transfer switch. Fixed wiring at property is PME and is up to date, having recently been re-wired. All circuiys protected by 30mA RCD or time delayed RCD at the distribution board.
The generator also has a 30mA RCD protecting the 63A/230V outlet - presumably to protect locally plugged in appliances rather than as standby power for a fixed installation. Generator is approx 50M from house, connected via 35mm csa SWA 3 core cable.
This where I run into problems with BS7671 recomendations. If I install as earth rod at the generator end and connect the earth core of the SWA cable to the house earth wiring (at the transfer switch), the generator RCD will always trip instantly when switing across to generaor power. Disconnect either the earth rod or the earth connection at the transfer switch and the same thing happens. Disconnect both and it doesn't trip and this is the way I have left it at present after taking advice from various experts and the genset manufacturer and trying different things over a 10 day period.
I've done a few similar installs before - but with no generator RCD - and all has been well with the earthing arrangement as recommended.
What worries me about this installation is that it might be in breach of Regulations - if I read them literally. The genset has a neutral-earth link at the alternator. In theory, therefore it should be operating at zero potential. In effect, I am operating with a floating earth. In the event of a utility power outage, is it safe to assume that the house PME arrangement will provide adequate path for fault current? Would it have been better to bypass the RCD at the generator end? Just wondering if anyone has similar experiences because 2 genset manufacturers I've spoken to say they hit this problem increasingly - sometimes at the genset and sometimes at the distribution board.
The generator also has a 30mA RCD protecting the 63A/230V outlet - presumably to protect locally plugged in appliances rather than as standby power for a fixed installation. Generator is approx 50M from house, connected via 35mm csa SWA 3 core cable.
This where I run into problems with BS7671 recomendations. If I install as earth rod at the generator end and connect the earth core of the SWA cable to the house earth wiring (at the transfer switch), the generator RCD will always trip instantly when switing across to generaor power. Disconnect either the earth rod or the earth connection at the transfer switch and the same thing happens. Disconnect both and it doesn't trip and this is the way I have left it at present after taking advice from various experts and the genset manufacturer and trying different things over a 10 day period.
I've done a few similar installs before - but with no generator RCD - and all has been well with the earthing arrangement as recommended.
What worries me about this installation is that it might be in breach of Regulations - if I read them literally. The genset has a neutral-earth link at the alternator. In theory, therefore it should be operating at zero potential. In effect, I am operating with a floating earth. In the event of a utility power outage, is it safe to assume that the house PME arrangement will provide adequate path for fault current? Would it have been better to bypass the RCD at the generator end? Just wondering if anyone has similar experiences because 2 genset manufacturers I've spoken to say they hit this problem increasingly - sometimes at the genset and sometimes at the distribution board.