Air in heating syatem

[Sally2000]

Ever since we had thermostatic valves fitted to our radiators we get noise in the upstairs radiators that sounds like air being pumped around.
This only happens first thing in the morning when they heat from cold. For the rest of the day it's all quiet.
What's happening here? Should I get the plumber back?

 

[Jurassicspark]

Have you tried bleeding air out of the radiators?

 

[Sally2000]

Yes. Many times but it just comes back. There are no visible water leaks.

 

[jj4091]

Is your boiler loosing pressure after you have bled the radiators as well, if so it sounds like you may have a leak.

 

[Sally2000]

It's an old non condensing boiler. Haven't seen any need to change it and the guy who fitted the thermostat valves said it was still working well. I don't want to replace it until it fails.

 

[fixitflav]

Yes. Many times but it just comes back. There are no visible water leaks.

Sounds like it's an open vented system (F/E tank in the loft).

Does the gas coming out burn? If you don't know, try lighting it. If it does it's hydrogen produced by corrosion, and inhibitor needed.
The noise could be caused by high flow when cold as the TRV is wide open. You could try throttling the other rad valve to reduce initial flow. The room may then take a bit longer to warm up but will get there.

 

[Sally2000]

It's definietly just air.
I'll try playing with the TRVs and see how it goes.
Thanks for the advice!

 

[HERTS P&D]

Did the plumber turn the pump speed up?

Andy

 

[Stuckinarut]

Were downstairs fitted with TRVs? If so, check them for leaks.

 

[fixitflav]

It's definietly just air.
I'll try playing with the TRVs and see how it goes.
Thanks for the advice!

Have you tried lighting it?
I meant throttle the other valve on the other end of the rad.
As Herts P&D says, try turning the pump down if possible. It should be at the lowest speed that the system works OK.

 

[Sally2000]

Ther are three rads up and three rads down. All had TRVs fitted. The pump is on the lowest setting. I have checked all for leaks. Will try adjusting the valves at the weekend.
I really appreciate your advice. Thank you!

 

[Johntheo5]

Have you a open vented system with a F&E cistern (small tank) in the attic?
Is the boiler a heat only boiler with a external circ pump, if so can you post the exact make/model/mode/setting and a photo of any LEDs which may be illuminated on the front

 

[Sally2000]

The boiler is a Potterton Profile with no display. An external pump and a header tank in the loft. It worked perfectly since we moved in a few years ago. In September we had it serviced and had thermostats fitted on six radiators. Inhibitor was added to the water. Since then we have has this air bubbling around the upstairs radiators every day when the heating comes on in the morning.
We tried adjusting the radiator valves one at a time and it changes which radiators get the most noise, but nothing stops it completely. It's difficult to experiment with because it only happens first thing in the morning. After that it's quiet for the rest of the day.
We also turned off the hot water at the controller, but that made no difference at all.

 

[HERTS P&D]

Did the plumber turn the pump speed up?

Post a picture of the pipe going over the expansion tank in the loft.

Andy

 

[Sally2000]

The pump is on its lowest setting. It isn't easy to get up to the tank.