the whole system is working 3 port valve does the right thing when told, thermostat on water tank does switch on and off if turned manualy, pump is working, heating to rads works but....no hot water.
Hot water does flow into the tank and out of return pipe. both pipes get hot, too hot to hold for very long but water in tank not heating
There is valve on the return pipe, currently this is fully open, should this be closed to restrict the flow ? or is there some other problem.
Any advice appreciated?