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heat pumps and dual RCD boards new install

Newfutile

we have come across  heat pumps on type A dual (RCD) Residual Current Device boards.

BS7671 does not seem to saying anything on heat pumps, the heat pumps seem to have variable frequency drives.

is this a danger considering blinding may now mean half the property could have a blinded rcd and therefore no additional protection?

would it be reasonable to expect heat pumps to have its own double pole type B HP rcd ,will BS7671 be ammended to include what is likely to become a bigger problem as more are fitted?

  • 0

    Yes, it's entirely reasonable,  If we know that the heat pump (or any other machine) is liable to inject significant higher frequency current, or DC, into its incoming supply, then it needs its own rcd if the device in the consumer unit cannot respond adqeuately - and often it's a type AC or A & couldn't do so.

    Even if there were no earth-fault in the heat pump, and thus its own rcd didn't trip, an upstream rcd in the consumer unit could easily trip, or else be 'blinded' to an unrelated earth-leakage in a different sub-circuit.  If we were determined to squeeze the heat pump circuit into an exisiting consumer unit, if single phase, it would need to be rated at not more than 11kW (50A), it would need to have a type B rcd with a switched neutral, it would probably need two DIN-module spaces & it would need a modified (split or further split) busbar to give it its own separate feed. 

    A separate consumer unit, (not fed from the main one), would be the sensible option.

  • 0 in reply to David Renshaw

    Not forgetting that the heating capacity is quite a lot higher than the electrical load. They are 'just' fridges in reverse ;-)

    A 12kW heat pump may only be a 6kW peak electrical (guessing figures a bit based on poor CoP values). Always check the specs!

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