Having to keep bleeding air from combi system

[marb]

Since we had a combi boiler fitted we have had no problem with having to bleed the air out. A few weeks ago we had TRV fitted to all rads bu the bathroom which is on the end of the line. Now every few days I have to bleed air out like I used to with the old gravity system. I thought a sealed unit wouldn't need bleeding ?

 

[petertheplumber12]

Inside the boiler or sometimes on top of it there is always an automatic air vent commonly known as an AAV, It is usually on the pump assy and it has a plastic cap on it, When fitted the plastic cap has to be undone half a turn. Check that that has been done. If the cap (looks like a tyre valve dust cap) is already loose then the AAV is not working properly and needs checking or changing.

 

[OwainDIYer]

Is it air or hydrogen? test carefully with a match.

 

[marb]

Funny enough we have had the boiler for just over 2 years and never had this problem. Just of late it has made some funny noises when running hot water to the bathroom. Will check what you advised though.

 

[marb]

Is it air or hydrogen? test carefully with a match.

Very funny.

 

[nitro23456]

No, thats genuine advice.

If something is corroding inside the system it will give rise to hydrogen production.

 

[gigz]

Turn the boiler off, bleed all the rads making sure you dont miss any out, as said check aav is ok, re-fill then turn the boiler back on. Make sure there's inhibiter in the system as well.

 

[marb]

There was inhibitor before he drained the system but he didn't put any back in. How do I get it in myself ?

Still having to bleed the bathroom rad. Bedroom rad cold at the top (can't bleed as bleed screw rounded off) and other bedroom rad cold at bottom.

 

[marb]

Why oh why did I bother having TRV's fitted. Ever since it has caused problems. Bedroom rad set to number 3 but not coming on despite being cold in there. When I turned it up to 4 or 5 it started bubbling and letting water in but only warm in patches all over the rad. It doesn't make sense. Looks like trapped air but this never happened before I had them fitted. How can a rad be cold in patches up and down all over the surface ? Why are the TRV's not turning on when set high enough ?

Answers on a postcard.

 

[marb]

To make matters worse I cannot bleed the rads with air because the bleed screw has rounded making it impossible for turning with the key.

 

[kbdiy]

If the bleed screws are rounded off then you've go no chance of getting all the air out hence the reason they're cold at the top.

What kind of rads are they? Can you remove the entire bleed screw fitting or are they built-in to the rads?

 

[marb]

You can turn the valve head as a plumber has done them in the past but I can't budge them as I don't have a wrench, only adjustable gripping pliers.