DIY Doctor UK DIY Forums

Seven months ago I had a problem. Radiators upstairs worked perfectly, but the downstairs radiators remained cold. After discussion and research, I decided to replace the CH pump. The system then ran perfectly.
The very same problem has now returned as the heating was fired up for the first time since spring.
I have since, turned off all upstairs radiators and the heat returned to the downstairs radiators. I then partially turned on the upstairs radiators to ‘balance’ the system and all appeared to work well.
I then switched off the central heating, allowed the radiators to cool and switched the heating on again. Oh dear … heat upstairs, nothing downstairs!
Is it possible that the replacement pump may have failed after only 7 months or should I be looking at a different cause of the problem altogether.
Radiators (and pump) have all been bled.
I would be extremely grateful for any advice to help me rectify this situation.

The most likely problem is still with the system not being balanced correctly.

Firstly, check the pump is set to speed three then shut the lockshield valve on the hottest radiators and then open it by only one full turn.

Have you checked that the bypass if fitted is not open too far? Have you made sure the hot water cylinder lockshield is not open wide too?

Proper balancing can take several attempts. Keep trying!

Thank you very much - will investigate further and follow your advice on balancing.