A friend is letting out a ground floor barn conversion which has underfloor heating run by a 12kw heatrae sadia flow heater,phoned me up to say boiler is leaking.That was an understatement,it had burst and if I didn't know better I would say it had been frozen,(quite possible).Anyway,replaced it and refilled system,when turned on I get a hot flow as far as the mixing valve and no further,the mixer/ manifold setup is one brass casting incorporating the pump,mixer,air bleed and two bolt on manifolds,there are two adjusting screws,one near the flow/return boiler connections and one opposite the mixer thermostatic head neither of which appear to do anything.Both pumps are running and the flow telltales are all up.Times being what they are I don't want to tell him its fk'd so any ideas would be appreciated.
