Air in System

[keithmdw]

I have a Potterton Promax HE system with 3 rads downstairs and 4 upstairs.

The bathroom and bottom of stairs are the first to get hot when the heating is on.

For a while now I have noticed that there seems to be a lot of air in the system - there is an air/water noise through the pump when it kicks in for a few minutes and the boiler seems a little louder at this first stage too (guess the air going through it's pump).

I have tried bleeding them, and the radiator at the bottom of the stairs always has an amount of air in every couple of days. None of the others have any air in when bled.

There are no obvious leaks in the system and everything is running fine - perfect heat (too hot if anything). One of the upstairs rads is turned off with the rad valve, all other rads are on full.

There have been many problems with the system in the past - 3-port valve heads replaced 3 times, several boiler repairs (nothing to do with water or pump). Also the 3-port valve body was changed recently as it was leaking - the radiator at the bottom of the stairs was removed to drain the system for this.

Like I say though, there are no leaks obvious anywhere and everything seems fine, so can't figure out why there would be air in it.

Could anything in particular be causing it, and what can be done about it?

 

[gas4you]

Check the auto air vent in the boiler is working.

 

[Soggy_weetabix]

and if it is not, please ensure it has a check vlv before you decide to remove and replace it.

David

 

[keithmdw]

Thanks for the replies.

What does this valve actually do?

Also, if this is to blame, and as everything is working perfectly, what is the consequence of not doing anything about it? I am happy to bleed the rad every few days until winter is over if need be rather than interfere with what is temperamental system at the best of times.

EDIT: Just remembered that whe the system weas drained to replace the 3-port valve body the plumber fiddled around with a verticle bit of pipe to nowhere in the tank/pump cupboard - it had a little screw on it he twisted to bleed air out if I remember correctly. What is this, and is there any harm in me (a non-plumber) doing the same?

 

[twgas]

if you've got no leak your problem is either air being drawn in from around the header tank (open vent most likely) or your system is gassing, which is caused by corrosion. EIther way it needs to be sorted as sludge will soon become an issue, if it hasnt already.

 

[keithmdw]

Thanks. I will check that valve on the end of the bit of vertical pipe in the tank cupboard and see if the plumber tightened it properly when he used it.

When he drained the system he commented on how clean the water in it was - it looked like drinking water.