radiators cold upstairs, hot downstairs?

Hi - I have 3 radiators out of 4 upstairs that are cold. Downstairs are hot. Ive changed the valves, bled them all and had the system flushed. The leg is hot on one of the broken ones but it still fails to heat the raidators.

When I turn off all valves downstairs my combi shuts down after 20secs after the temp hits max.. any1 know what could be wrong. already spent £500 and I still have cold rads :( any help is appreciated. ta

mark
February 2010

Thanks for the info. I have managed to trace the fault. There was a check valve (one way valve) in the upstairs circuit. It was completely blocked. It was very hard to find as it was hidden under the floor. Replaced it and the radiators upstairs are working fine.

Gary
December 2007

valves seized on the rads ?

dave
November 2007

Is the pump working and do the zone valves open? If you had a blockage on the return I would have thought the pump would burn out. Do your rads downstairs heat up quickly after you switch the heating on? If not could be the zone valve is sticking inside and not sending the hot water around your heating system. All that happens then is that the hot water from the boiler heats the cold water in your heating loop by convection (I think) ie if you touch a warm pipe then your hand gets warm. Does that make sense? If you take the motor off the top of the zone valve you can turn the nut with an adjustable spanner. Firstly I'd get someone to turn your heating on and off whilst you get up close to the pump and valves and make sure you can hear them operating.

James.
October 2007