boiler is heating radiators from the return pipe when hot water only is selected. I have changed the non return valves and both pumps are working independently, all valves are open on the system and there is 1 bar pressure. A head scratcher! any help.
have you checked the system water? if its full of glar and sludge the nrv's will just stick open again! the only way heat can get to the rads from the hw setting is through the nrv on the pump there is no other waterway between the heatstore and the htg pipes. it has nothing to do with the vessel!
also remove the head of the pump to check that something hasn't damaged the impeller in case small parts are breaking off and sticking in the nrv! it's not common but ove came across that before!
Boris the brave, July 2012
In answer to manwithnoname, The wiring is fine only i suspect the expansion vessel has blown and needs replacing hence the backflow, any opinions?
steve the plumber, May 2012
DHW heating RADS
ive only known FLOW pipe to heat up when this happens
ive never known RTN pipe to heat up
is the DHW pump spinning the right way?
check live & neutral connections on pump & pcb are correct
