I have a Megaflow unvented heating system Model 140.
Hot water OK...Boiler works in kitchen. Thermostat 'clicks; when turned up to higher temperature in hallway and the control unit shows both hotwater and central heating as being on BUT I have no central heating to the house, up or downstairs.
I cannot locate anything that looks like a pump in the airing cupboard next to the Megaflow so have no idea if the it's the pump that is not circulating hotwater round the radiators or not as I'm led to believe that there is a variable flow switch on most central heating pumps which may have helped if turned up.
Made sure that all switches are in correct position and have run out of ideas.
Sounds like the two port motorised valve to the radiators is not moving, locate this valve and manualy switch the valve to open, should be some kind of leaver depending on make. The leaver may be quite stiff as there is a spring trying to keep it closed. If after moving it to the open position you get heat to the rads then the valve may need changing. Depending on the make you may just have to change the small synchron motor cost about Â£12 + Vat, or you may have to change the entire head can be about Â£45-Â£50 + Vat either of these soloutions avoids draining down the system. The last option is to have to change the entire valve Â£50-Â£55 + Vat then you will need to have the system drained down.
Do not get mixed up by the Honeywell two port valve on/close to the Megaflow, you are looking for the radiator equivalent to that one.
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