FoxESS Community - Owners & Installers Forum

I would assume that a Type B RCD be used, however, it appears the Fox manual notes "Fox ESS recommends the use of a type-A RCD" on page 3.

When the F3600 is in the same CU as an inverter driven heatpump that requires a Type F or B RCD it seems a tad strange?

Can anyone clarify.

The inverter has an internal RCD that allows it to disconnect it’s live conductors if it exceeds DC thresholds (which performs the actions of a type B RCD) - the fitting of an external Type A RCD is the only UK requirement.

Excellent, so a type B for the HP has no effect on the F3600.

The bigger issue may be the sizing, Fox recommend a minimum 100mA RCD so as long as your not on a 30mA breaker you should be ok.

Its on a 80a 30ma RCD Type A via a 20 Amp Single Pole Type B 6kA MCB. What issues should I (along with hundreds of others with this set up !) expect

With a 30mA RCD you may see inadvertent trips, some RCD’s trip out well below their rated limit and the problem with multiple devices all sharing a single RCD particularly those with large heating elements, pumps etc.. they combine very quickly to overload the trip limits and a heat pump and inverter on the same 30mA RCD is probably too close.

The best way forward is to have a CU with a 80A (or 100A) isolator and then use individual RCBO’s each rated to the device that is connected to it.

Thank you Dave, that's very useful information.

It's a shame the Napit, NICEIC, and MCS certified installer couldn't work that out)