We had been using this guy to repair our ground source heat pump for the longest time, because we had thought other services couldn't deal with that kind of a system. He specialises in ground source heat pumps. He's very squirrely and constantly pushing back times for deliveries and repair work. We recently found another company and had them install a thermostat. Apparently the guy at Donwel had wired everything up correctly, but used the wrong colour coded cables to connect. Easy for him to understand, but not others.