Air keeps coming back in sealed heating system - no pressure drop

[sapphire]

Hi Everyone

I am new here! I hope I can get some help with a problem that I have had with my sealed system since it was installed in October 2011. I am in London SW8 and have a problem with my heating system that I have been unable to solve.

I have 2x Heatrae Sadia MEGAFLO 145litre cylinders which are indirectly heated by a Vaillant 428kw open vent boiler.Even though these were installed in October 2011 and I am still bleeding air from the system and there don't appear to be any leaks at all.

The cylinders are located in the cellar and I have 2 manual air vents in the main bathroom at the highest point of the circuit that is used to heat the water and the heating system which runs from the boiler and into the coils at the cylinders. There are motorised valves which open up to heat the radiator heating circuit radiators when heating is demanded.

It seems that no matter how much I try, I can’t get the air to leave the system. If I bleed it manually via one of the manual bleed valves, I can come back in a day and do it all again. The pressure seems to remain at 1.2 bar on the heating system no matter what I do. I am sure there is no leak at all as the pressure doesn't drop even after years, so somehow air is entering my system.

I also get air in the highest towel radiator on the top floor, which I bleed. I am thinking that as I will shut down the radiators soon, the motorised valves will only work for hot water and not the heating and so the radiators should not fill with any air.

I have thought that perhaps my expansion vessel is inadequate as I have 14 radiators currently connected to this expansion vessel. Or, perhaps the expansion vessel is faulty? I have attached pictures of the setup in the cellar and the flow/return pipes that head to the boiler. The heating water is pumped by the red Grunfos pump which has been fitted to the return of the heating system water.

The flow/return pipes do have a fair distance to travel to reach the boiler from the cylinder. They go up 1 storey and travel under the bathroom floor and then down through the kitchen ceiling directly into the boiler.

Does anyone have any ideas on what I can do? At the last service, the system was drained and more inhibitor was added (I thought that perhaps my system was low and corroding). Can I test the expansion vessel or does it seem that the problem is elsewhere?

I hope you all can help?!:yesnod:

 

[chris watkins]

In some cases where the pressure at the top floor of a big house is virtually nil then micro leaks can pull air into the system. now you say you've increased the pressure and no more air problems i'd look for tiny water leaks on valves etc upstairs. If air can get in a sealed system then water can get out.

What in the same way that water comes out of non barrier pipe when used on sealed heating systems?
If you have 2 Bar on the gauge in the basement then your top floor would have to be some 19 Metres or around 6 floors above your head for there to be little or no pressure !!

 

[wild nomad]

What is the capacity of the expansion vessel?

If you have a lot of rads (which you do) it mat be that it is not big enough to take the amount of water expansion needed for the rads so the air just gets passed from one rad to another as you bleed them. Also the pump can add air into the system if it's set too high.

 

[sheff paul]

It's there mike-c so all us posh southerners can pug our electric tooth bushes in to recharge.
View attachment 18530 Mind you my I found the wife's one under our basin & it seems to have been used so much all the bristles have all come out.

when I found the missus,it looked like a cross between a 4cell Maglite torch,and a riot baton!

 

[sheff paul]

What in the same way that water comes out of non barrier pipe when used on sealed heating systems?
If you have 2 Bar on the gauge in the basement then your top floor would have to be some 19 Metres or around 6 floors above your head for there to be little or no pressure !!

Chris my mate never uses joint compound on his installs,and has mentioned a similar problem a few times

 

[Whyme]

Chris i meant leaks not plastic pipe and yes i have come across it and it does happen bud. even if its not a block of flats. Also the ops only just put 2bar in and says all is ok at the moment regarding air.

 

[Jimbob]

I doubt micro leaks are the issue. It's probably more the AAV sucking in air at top if system because pressure was so low as system head is too great!

 

[chris watkins]

when I found the missus,it looked like a cross between a 4cell Maglite torch,and a riot baton!

Wife wanted a new one, I suggested , until noise of motor lead to complaints from neighbours.
What are these women like paul ?

 

[sheff paul]

Wife wanted a new one, I suggested View attachment 18593 , until noise of motor lead to complaints from neighbours.
What are these women like paul ?

ohhh sends a shudder down one self..

 

[Whyme]

I doubt micro leaks are the issue. It's probably more the AAV sucking in air at top if system because pressure was so low as system head is too great!

Read post 13 dude.

 

[Jimbob]

Haha, then yes small
Leaks seem very lightly. Might be ok though, small leaks will only pass air

 

[sapphire]

Haha, then yes small
Leaks seem very lightly. Might be ok though, small leaks will only pass air

I still can't detect any leaks and it has stayed at 2bar pressure for a couple of days now. Surely if there were small leaks, the pressure would drop?

 

[Whyme]

Are there any pushfit connectors on the heating if so you need a bit of pressure to make the fitting bite and locate properly. if it isn't under any pressure the micro leak thought could be possible.

 

[sapphire]

Are there any pushfit connectors on the heating if so you need a bit of pressure to make the fitting bite and locate properly. if it isn't under any pressure the micro leak thought could be possible.

I actually don't know if there are any under the kitchen floor. As far as I know the whole house is soldered copper and compressions on the pumps and megaflo's but there is a chance there are push fits under the kitchen floor, but I will never know.

When we had this system installed, we changed all pipe work except for the pipes under the kitchen floor. Unfortunately, when our installers connected to the copper tails leading under the kitchen, they didn't fit any valves, so I can't isolate that area.

But, the pressure hasn't dropped from 2 bar, so I can't see how there would be leaks?

 

[Whyme]

Gawd only knows then. We could be guessing forever. As long as there's no water leaks (pressure drop) then alls good.

 

[Truman]

how much air are we talking? you will always get some air buildup in the high parts of any system.

Why is this the case? If a system is sealed and the water has given up any oxygen left in it, then where will this air come from?