boiler fires for heat but heat does not circulate, pump impeller spins and power to divertor valve which moves freely when not on valve. any ideas as what to check ?

dean welch, April 2008

yes it all moves freely and there are no zone valves on system. diverter stripped out and cleaned to no avail.
biasi tech centre think primary heat exchanger is blocked but i doubt this.
i think bypass my be stuck open.
so any more ideas appreciated.

deanwelch, April 2008

Does the valve mover freely too?
Does valve operator move also when you apply a little resistance, this would be the proper way to test it.

I assume the boiler get to temp really quickly, may even over temp and lock out. Have you any zone valves on your system that maybe stuck closed.

T, April 2008