Air getting drawn into sealed heating system

[marc1977]

Hi,

Ive posted this before but still not found the cause of the problem. I have a sealed S plan system with expansion tank that is drawing in air. I have to bleed one of the rads every week for 5-6 seconds. Details below:

1. The system is NOT loosing any pressure until of course I bleed the radiator. I left it alone for 3 weeks and the pressure when cold remained at 1 bar.
2. There is sentinal inhibitor in the system and i have also added sentinal leak sealant.
3. There are NO visible leaks anywhere. I have checked all rad valves and connections.
4. The expansion tank appears to be fine and has 1 bar pressure.
5. No visible leaks on the pump.
6. Worcester Bosch have been out and inspected the boiler and found no issues.

What the Damn is going on?! Have I got a magical heating system that defies the laws of science?

Many thanks

Marc

 

[Harvest Fields]

How many radiators do you have? are they small or large? Are they doubles or singles and how much inhibitor did you put in to the system?

 

[marc1977]

Its a big house..15 rads with 2 very big doubles rest are singles. Lots of drops too if that helps as downstairs floor is concrete.

I put 1.5 bottles of sentinal in.

Also Ive tried igniting the gas but it didn't ignite so dont think its hydrogen.

 

[Harvest Fields]

Sentinel x100 is a good inhibitor but for a system your size I would use 2 x 1 litre bottles. As a 1 litre bottle only does 8-10 rads have you have the condition of the water in the radiators tested?

 

[marc1977]

No. I should mention all the rads are new and the system was drained down and refilled 6 months ago. Most of the pipe work is new too. Can you buy testing kits for the water?

 

[Jay The Plumber]

did you check the expansion vessel pressure when the system pressure was at 1 bar or did you drop the system pressure to check it?

 

[marc1977]

i did it when the system was cold.

 

[Jay The Plumber]

i did it when the system was cold.

and the system pressure was at 1 bar cold ?

you normally need to drop the system pressure below the pressure that the expansion vessel is charged to.

 

[Last Plumber]

Where is the pump in relation to the expansion vessel ?
Can you post a photo of the installation of the pump and vessel?

What pipe material is it?
If it is plastic, is it the correct one (barrier) ?
Most of it is these days but you never know !

 

[marc1977]

Last Plumber,

Photo attached. All pipework is copper.

Jay,

So the expansion vessel has to be below the pressure of the system??