Been having problems with the domestic hot water not getting up to temperature. Given we have solar thermal, solar PV, underfloor heating and an Air Source Heat Pump, the engine room (as I call it) is awash with pipes, manifolds, control boxes and pumps, finding the fault is a bit beyond my limited engineering skills.
Called in a plumber who pronounced a problem with the Air Source Heat Pump outdoor unit. Called Mitsubishi, who took a week to organise a refrigerant gas qualified plumber to call. He tested the system over the span of an hour, topped up the refrigerant (it was 300gm short) and left. There was a slight improvement, but still the water wouldn't reach more than blood heat.
Finally went over the system myself and discovered the pump that draws water from the Air Source Heat Pump was too hot to touch and wasn't making the usual hum when under load. Obviously the pump had failed. Hit it a couple of times with a 2lb fine adjustment instrument (a hammer) and it hummed into action and the water temperature on the control unit immediately shot up.
Despite it now working, the pump needs to be replaced as a precaution for winter, as it also feeds the underfloor heating.
Should I call out a plumber to replace it, or just do it myself?
Why the hell couldn't a plumber find the problem?