Our biggest problem was exactly what you have said, plumbers not knowing what they were doing from the main contractor down to their two subcontractors but the actual pipe work isn't bad at all that is if you forgive them for installing the two houses with the same pipe work they bent for one!!! The sub contractor that professed to be heat pump engineers made a fortune installing this sort of technology to the council, a fortune.
So anyway we ended up, passed by our ex council's building control officer, with the system plumbed back to front, our tundish is around the back of the tank as is one of the immersion heaters, which if ever needs replacing will have to be done by a midget contortionist trained as a plumber, we have been told that correcting the plumbers work would be as costly as installing the system.
But with the house now properly insulated and drafts kept to the minimum the system now works well and brings the house up to 20 degrees quite fast.
So anyway we ended up, passed by our ex council's building control officer, with the system plumbed back to front, our tundish is around the back of the tank as is one of the immersion heaters, which if ever needs replacing will have to be done by a midget contortionist trained as a plumber, we have been told that correcting the plumbers work would be as costly as installing the system.
But with the house now properly insulated and drafts kept to the minimum the system now works well and brings the house up to 20 degrees quite fast.