Hi, I have a gravity fed system, with a pump attached to the boiler downstairs. the cylinder has a motorised 2 way valve on it and a thermostat. I have turned off the CH but the upstairs rads remain on. I have tried moving the 2 way valve by hand 90 degrees , but it seems i get just rads and no hot water at all that way. I have looked for a check valve but can't find one, any sugestions?
There many systems I will guess you are on C plan. This relies on the resistance through the pump to stop central heating water from circulating and if the water has not fully cooled in the radiators before the domestic hot water calls thermo siphon can take place. Easy cure is TRV on up stairs radiators. Honeywell website does show the SUNDIAL PLANS DETAIL sorry not allowed links. Also on my site but same problem not allowed links
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