I have a rental home with a single standard Hagar RCD (it came with the house, so I don't know what type it is). When I installed a wet underfloor heating system, I installed a 'smart' eco circulating pump. Each time the circulating pump turned on, it caused the RCD to trip. I replaced the circulating pump with an old classic Grundfoss pump that I had as a spare, and everything works just fine. I'm pretty sure the 'smarts' in the eco circulating pump are generating voltage spikes and associated current 'leaks' that are causing the RCD to trip, because the UFHC supplier sent me a replacement 'smart' pump and it behaved exactly the same way, tripping the RCD whenever it turned on. Which RCD type would be most tolerant to spurious voltage spikes caused by a 'smart' pump motor, but still be within regs?