Sealed system gaining air.

[Matt0029]

Any ideas on why/how a sealed central heating system with a combination boiler would continually gain air? The system is newish 10 year old house and the system water is clean so I I think that rules out corrosion causing creation of air in the system.

 

[ShaunCorbs]

Have you closed all of the auto air vents ?

 

[Aquarius]

Gain air? As in you need to keep bleeding rads?

 

[townfanjon]

Any eggy smells when you bleed a rad

 

[Aquarius]

Any eggy smells when you bleed a rad

Depends what he ate the night before 😄

 

[Matt0029]

Gain air? As in you need to keep bleeding rads?

Correct yes. The system also appears to gain pressure. The filling loop is disconnected l.
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Have you closed all of the auto air vents ?

There is just the one inside the boiler, that is currently open.
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Any eggy smells when you bleed a rad

Not that noted no.

 

[Aquarius]

If it’s gaining pressure and the loops disconnected, I’d be looking at e.v. or failed plate hex. With the bleeding of rads, I’d be looking for a leak, or trapped hydrogen. Is it all rads? I find not then try isolating the affected rad/rads and see if the issue remains.

 

[EvilDrPorkChop]

I've got the same issue with a Sealed system. Rads get Air in, but pressure doesn't drop.... Don't really understand where the majority of the water is going though as all of upstairs had air in - baring in mind a few months before the system was drained and refilled and bleed fully.

All auto air vents closed.

Must be corrosion as it's been flushed when we fitted new boiler. Was quite dirty, and filter has picked a bit up. There must be a rad somewhere corroding but trying to pin point the rad might be interesting...

 

[Matt0029]

If it’s gaining pressure and the loops disconnected, I’d be looking at e.v. or failed plate hex. With the bleeding of rads, I’d be looking for a leak, or trapped hydrogen. Is it all rads? I find not then try isolating the affected rad/rads and see if the issue remains.

It's just the upstairs rads. Can an expansion vessel fail in a way so that it lets air from it in to the system? I have tested the scrider valve on it and releases air so the diaphram isn't split. I did re charge the vessel as the charge was low. But the problem has carried on.
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Have you shut the auto air vent on the boiler. Can these sometimes suck air in to the system?

 

[Aquarius]

It's just the upstairs rads. Can an expansion vessel fail in a way so that it lets air from it in to the system? I have tested the scrider valve on it and releases air so the diaphram isn't split. I did re charge the vessel as the charge was low. But the problem has carried on.
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Have you shut the auto air vent on the boiler. Can these sometimes suck air in to the system?

I wouldn’t have thought ev would allow air in. If it’s all upstairs I’d be looking at a leak, but unsure why it would gain pressure. Did you charge vessel correctly?

 

[Matt0029]

I wouldn’t have thought ev would allow air in. If it’s all upstairs I’d be looking at a leak, but unsure why it would gain pressure. Did you charge vessel correctly?

A leak that was pulling air in?
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Yes I depressurised the system and pumped up to 0.75bar

 

[Aquarius]

A leak that was pulling air in?

You mentioned all upstairs rads, and you also mentioned they need bleeding, so to me either hydrogen buildup from sludge, or a leak causing the rads to empty and need bleeding.

 

[Matt0029]

Is there anyway of testing the air/gas that is released when bleeding the rads. To see if it is hydrogen build up from sludge? I am going to drain the system so will see if it is sludges up. I don't think it is. Is only a 10 year old system. New boiler installed 2 years ago. Inhibitor added or so it says.
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Have you closed all of the auto air vents ?

I did plan on shutting the auto air vent on the boiler after I have filled and fully bleed the system and had it running for abit.

 

[ShaunCorbs]

Put the gas into a fire proof container eg aluminium can let the gas into the can 5 seconds should be enough and see if you can light it eg torch across the top of the can

 

[Matt0029]

Thanks should shutting the auto air vent on the pump after being fully bleed and run for abit be OK? Or do these really need to be kept open.

 

[ShaunCorbs]

Thanks should shutting the auto air vent on the pump after being fully bleed and run for abit be OK? Or do these really need to be kept open.

yep let it run for an hour or two then close