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I have a problem with air in the central heating system. It is a wall-mounted boiler (not a combi) in a bungalow with 13 radiators, the final few meters to each radiator are in 10mm pipe. There is an indirect hot water cylinder.
I had to fit a new pump recently after replacing it only two years ago. If I set the pump speed at the middle setting the radiators, particularly those close to the boiler, fill with air very quickly. Two fill with air in under an hour. I have checked the entire pipework and there is no sign of a leak. There is a overflow pipe going into the loft, I have placed a plastic bag over the end and sealed it to see if it was drawing air. It 'breathes' slighlty, but no evidence of it trying to draw air. The system continued to fill radiators as normal.
The header tank in the loft seems to increase its volume after the system has been running for a while, but not enough to reach the top of the tank.
When the system is running there is a distinct sound of running water from the boiler area as well as the hot water cylinder area.
I moved the pump switch to the lowest setting and the air seems to have subsided. The problem is that at this level the radiators don't get as hot as I'd like.
I can't understand where the air can be coming in. With the overflow sealed with the plastic bag the system is effectively a closed circuit, so where can the air be getting in?
I wondered if the hot water cylinder might be letting the air in, but I don't know how to tell. The hot water is behaving itself, is not discoloured.
I would appreciate any guidance I can get.
I had to fit a new pump recently after replacing it only two years ago. If I set the pump speed at the middle setting the radiators, particularly those close to the boiler, fill with air very quickly. Two fill with air in under an hour. I have checked the entire pipework and there is no sign of a leak. There is a overflow pipe going into the loft, I have placed a plastic bag over the end and sealed it to see if it was drawing air. It 'breathes' slighlty, but no evidence of it trying to draw air. The system continued to fill radiators as normal.
The header tank in the loft seems to increase its volume after the system has been running for a while, but not enough to reach the top of the tank.
When the system is running there is a distinct sound of running water from the boiler area as well as the hot water cylinder area.
I moved the pump switch to the lowest setting and the air seems to have subsided. The problem is that at this level the radiators don't get as hot as I'd like.
I can't understand where the air can be coming in. With the overflow sealed with the plastic bag the system is effectively a closed circuit, so where can the air be getting in?
I wondered if the hot water cylinder might be letting the air in, but I don't know how to tell. The hot water is behaving itself, is not discoloured.
I would appreciate any guidance I can get.
