Isolate Mains Power to appliance as per TOPs P4
Close heating flow and return valves and drain through safety valve
Remove return valve spindle guide assembly
CAUTION:
Be careful not to damage capillary tube of thermostat close to the return valve
Close heating flow and return valves and drain through safety valve
Remove return valve spindle guide assembly
CAUTION:
Be careful not to damage capillary tube of thermostat close to the return valve
Observation:
Examine for blockages or dirt.
Isolate as per TOPs P4
and refit as necessary