What's making my Combi make a strange noise?

[RichD1]

Drained system down and flushed it through a couple of weeks ago to replace the cleaner with inhibitor. Filled back up and bleed the system and everything was fine. But I've noticed recently that when hot water is on the boiler sounds like it has air in it as it swirls and gurgles faintly. On CH there is no noise.

When I bleed the system after filling I did open the air lock valve on the top of the pump and also the large screw head on the front.

Any idea what is causing the noise.

 

[RichD1]

Having done some more reading on Google, is it the AAV that needs bleeding. I also see there is a program P.0 which can be used after filling the system.

Should the AVV knob be opened or closed? When I did the flush through I discovered water had dripped out of the boiler on investigation I found that it was coming from the AVV as the cap was loose. So after re-filling the system I opened it until the air had stopped then tightened it back down. Do you think the valve should be open as implied by the auto bleed.

 

[muggles]

Well you've not said what boiler you have but I'm going to take an educated guess that it's a Vaillant or Glow-worm. You should be aware that removing the front cover on the majority of models in these manufacturers' ranges should only be done by a Gas Safe Registered Engineer as they form the safety room seal.

The AAV is there to help remove air from the pump during commissioning. It shouldn't generally need to be open all the time. They do have a habit of leaking

 

[RichD1]

Yes, it’s a Vaillant EcoPlus. So any idea why there is an air sounding noise on HW and not on CH?