The system had to be recently drained to fit a new radiator. It was then refilled (to correct pressure) and worked just fine, the radiator had to be removed and re attatched. again system drained and refilled, bled etc. Now it will produce hot water just fine but will not fire the radiators. The water pressure is just fine and I have checked the water loss sensor, again fine, any ideas please?

markus, August 2008

Is the pump running. Does the boiler fire at all in heating Unplug the timer this puts the boiler in the on position. it will also prove the clock. If no improvement. Were THE ISOLATING VALVES ON THE JIG TURNED OFF ?.

Bendan, September 2008

try moving the reversing valve lever between dhw and ch. when you turn on the timer for ch , are you hearing a click from the timer? these were a fairly common fault on 623's and cannot be repaired. sometimes isolating at the spur for a minute or two can reset them

kieran, August 2008