The ASHP will "slow down" as the energy is not being removed that it is adding. Just like a modulating boiler....
Remember that the underfloor loops share water with the heatpump but aren't directly connected due to the magic of the mixer valve...
A high resistance on neutral might do it (as there's always *some* leakage current to earth) but it does sound like it's the RCD.
but whenever you *do* get the RCD to latch in and the lighting MCB trips it that does allude to a problem with that circuit. Is there an extractor fan in the loo perhaps?
Where is the power coming from for the van? What kind of cable? Is there an earth rod?
I wonder if being powered ON all the time will actually slow response tho- even with no flow or energy input aren't they going to close down to try and maintain a deltaT? How will they then respond to a very slow rise in supply temp?
I've recently bought a Cool Energy 9.5kW unit and it was easy to instal and has a pretty intuitive controller. Temperatures can be set freely for heating or cooling...
but when did folk become so combative and thoughtless? Didn't seem to be an issue when *everyone* lived in rented terraces with outside loos...
and don't presume everyone in the countryside is neighbourly.