Strange Central Heating / Radiators issues

[scotthud]

Hi, ive noticed that 3 of the downstairs radiators dont get hot when the heating comes on, all the others in the house do (6 upstairs and 5 downstairs do) after reading on here and other forums/youtube ive tried to rebalance the radiators, all got hot, great i thought, then the hot water kicked in and the downstairs radiators got cold, i turned the hot water off and the downstairs radiators all heated up again?

Is it the pump Gundfos Alpha 2 ? sat at 32w, the valve seems ok as it switches between W M H ?

Thanks as alwyas

 

[terryplumb]

See if the hot water cylinders flow / return pipes (to the coil inside the cylinder) are fitted with a gate valve on either of them ,which is used to throttle down the flow into the cylinder.
How long have you lived at the property,and when did these radiators start to not heat ?

 

[scotthud]

lived here since it was built over 20 years, what do you mean by a gate valve?

 

[fixitflav]

lived here since it was built over 20 years, what do you mean by a gate valve?

But is it a recent problem?

 

[terryplumb]

lived here since it was built over 20 years, what do you mean by a gate valve?

It's a brass valve on a pipe ,they often have a large ,round ,red coloured wheel head handle. But not always.
As asked already ,when did the cold rads problem start ?