Constant Air in CH System

[garjen]

I have a pumped open vent CH system suppling hot water and heat to 9 rads.

My problem is that I am constantly venting air from the upstairs rads (daily)

I have recently change the boiler to a Ideal Icos HE18. Air still getting in system!
I have changed the pump. Air still getting in system!
I have cleaned the system. Air still getting in system!
I have checked the complete system of leaks. there are none.

All the above need to be changed anyway and I hoped that these replacements would resolve air problem, but didn't.

I have no idea what to do next. Can anybody suggest answer to this problem

 

[ChrisR]

Usually a system design problem. Vent should be close to boiler, with feed just after it, then the pump. Is yours like that? Try holding a glass of water under the vent pipe. If it sucks water when the pump comes on, it would be sucking air when in use. On the other hand, water should never come out of the vent pipe.

 

[garjen]

No my system is not like you say.

The vent is just before the pump, but the feed is on the hot water return to the boiler.

The vent does suck which looks to be the answer to where the air is coming from.

How do I get over it please? Can I change the feed to joint vent and feed?

 

[oilman]

Is the feed pipe restricted or blocked?

It would be better to move the feed pipe to just after the vent pipe.

 

[garjen]

I have drained off some water and it seemed to take a long time to top up the system, so there may be some restriction. How can I unrestrict it and is that possible?

Unfortunatley there is not enough room, the vent is only about four inches from the pump. So major plumbing required to conform.