Indeed, everything you say makes sense and aligns with the HP and PV manufacturers.
I have now identified the issue.
· My Heat Pump manufacturer states that if an RCD is used it should be either a type F or B (Type B is the preferred option).
· My PV Inverter states the RCD ‘can’ be a Type A or B (because it has Type B RCD on board), however, it requires a 100-300ma RCD due to potential tripping if a 30ma RCD is installed.
From that, I would need a split board or use single pole RCBO’ as you rightly noted. Although I’m unsure (don’t have the knowledge) how many slots that configuration would take up. My second CU is a 6 way Niglon, and they don’t have the extensive range of components like Hager.
Out of curiosity. On page 8 of the guidance document you uploaded, it notes “If Type A is selected for the heat pump circuit, the upstream RCD must be either Type A, or Type F or Type B.”
How does that relate to my heat pump MCB being a C Curve and the RCD being a Type A, does it have any significance with that statement?
Finally. I can still hold the original installer to account if I can show that they fitted a Type A RCD incorrectly. Does Amendment 2 of the BS 7671:2018 IET Wiring Regulations (BS 7671:2018+A2:2022) demonstrate that during early 2025 the electrician should have fitted a Type F or B RCD and not a Type A ?
Let’s not go down the recent debate over Type B High Performance RCDs that function at high-frequency currents. ☹