Hot radiators uptairs when heating is switched off

[stephen]

My heating is a pumped system with a Mid position Valve. When I switch off the Central Heating and leave the hot water on, the upstairs radiators heat up and the downstairs are just noticeably warm. The Mid Position valve is working as it is cold on the CH side. Any ideas what is causing this problem.

 

[AnonymousImport]

Conceivably, the return from the cylinder to the boiler is going via the rads, but the wrong way, i.e. rads not plumbed correctly. To check, when you turn on the hot water, do the rads start to get hot from the wrong side ( opposite side to when you have heating on)?

 

[MANDATE]

If problem is as suggested and you have 15mm copper pipe, you can fit a 'spring loaded one way valve'somewhere suitable in the circuit.
These are available from Wickes or they were a few years ago, £3 to £4.