30 Nov 2022
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United Kingdom

I have an unknown UFH system (not long moved in) that had to have the blending valve replaced due to a leak. I was worried that this would have introduced air into the system so now am looking to refill/pressurise the system (the emergency plumber just did the blending valve and said it was getting hot on the feed so left).

I've now got 4 runs (in different thermostat controlled zones) that aren't heating up. In the picture they are the ones without actuators/caps on. I've given the actuator pins a good wiggle and they (now) seem fairly free but the run never gets warm.

The flow feed is at the bottom and they are all hot (some showing no flow according to the meter but the run is working fine) and I can feel the return pipes getting warm too. However for those 4 runs the returns are cold.

I have tried to just heat these 4 runs and no others but they still remain cold.

So I have a few thoughts:

Could this be a balancing issue?
Could this be an air lock?

I want to refill/repressurise the system but was advised to fill from the top? This seems wrong to me as it would on the return side and not the flow? Does it matter?

Have I missed anything obvious?



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