Hi all,   I’ve been a long time lurker, but this is my first post on the forum... of course it’s because I have an technical problem that I need help with, and based on all the previous discussions on here I’m thinking there is more than enough experience to enlighten me!   I have a 4kw Kingspan Aeromax Plus KHP0041 (made by Carrier), heating my UFH system downstairs and radiators upstairs,  all was working fine until...it wasn’t.   I have 240v in the unit, but no b