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Air in heating system


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Recommissioned the heating a couple of weeks ago, just before I went off on hols.

As we had done some work on it over the summer, lowering a radiator and replacing two others, I comprehensively bled all the radiators as the system filled.

Just had time to test it for a few hours, to find that the radiators are not getting as hot as they should be. Bled the radiators (again) to find that plenty of air had got in.

Although the boiler (contained within an oil fired range) seemed to be getting hot, I could put my hand on the flow pipe where it exits the boiler, with a minimum of discomfort.

I then bled the upstairs radiators AGAIN to find that more air had got in...

The system always used to get air in it, and I have had to bleed the upstairs radiators constantly over previous winters but never as much as this.

It's a vented system with no valves; when the pump is off for the heating the water is meant to still circulate via gravity to the hot water cylinder (although the water heating has never been very effective).

Any ideas? ?:|

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Where does the new water come from? If it's a header tank the ball valves can get stuck. By bleeding you just move the water about..............

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or corrosion?

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Could it be sludge muck & grime that tends to settle in the bottom of radiators been moved about when you drained the system...

now left restricting the flow through some parts of the system?

especially if hot water part is relying on gravity flow not pumped..

had any sludge remover..

or inhibitor fluid treatments..

in the system recently?

wheres our heating man gone?:(

:|

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Was the heating On or Off, when you Bled it?

Because I remember a Plumber telling me years ago that people (myself included) make the mistake of Bleeding the rads with the heating is on.

He said that that just put more air in the system, and that they should be bled when the heating is off.

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Was the heating On or Off, when you Bled it?

Because I remember a Plumber telling me years ago that people (myself included) make the mistake of Bleeding the rads with the heating is on.

He said that that just put more air in the system, and that they should be bled when the heating is off.

Yes, I have been told that too, so I bled it with the whole system off. It then seemed to fill with air pretty much straight away.

Header tank feed is all fine.

System has got pretty well flushed as we filled it once, then drained it down again to sort the leaky joints that my father had not sealed sufficiently... :|

The system was pretty sludgy when first drained but I believe it had inhibitor content (smell).

I doubt that the problem is a blockage (unless it is on the main flow) as all the upstairs radiators are similarly "hot" and all the downstairs radiators are similarly (less) "hot".

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you may find that the pump is sucking air in the vent pipe you may need to lengthen this or fit a re-stricter on it (can't think of the proper name for it, I had the same problem )

as for the rads not being at the same temp they need balancing on the lock shield valve on each rad

if the temp isn't very hot coming off the boiler turn the temp gauge up on the boiler

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you may find that the pump is sucking air in the vent pipe you may need to lengthen this or fit a re-stricter on it (can't think of the proper name for it, I had the same problem )

That is a possibility.

The upstairs will probably always be hotter to be honest, whether the rads are balanced or not, as that's where the circuit goes first. After that the flow goes all the way downstairs and under the floor, a fair way.

It's a range cooker so it's not just a case of turning it up - the boiler is getting very hot, it just seems that the hot water is not making it's way out of the boiler in sufficient quantity...

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Well we are still coping at the moment, although it is warmer outside than in... haven't needed to put the heating on yet.

However the woodburning stove which is being fitted on Thursday which will be very welcome!

Anyone know if there definitely is some type of air non admittance valve available for the vent in the loft, as it is new to me - I have only seen automatic vents before which I assume are different?

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I've been told that "air" isn't actually air... it nitrogen or something like that..due to a dirty/not treated system...

What I was told is you need to power flush, neutralise and then add inhibitor... I may be wrong though... JL is the man!!!

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I've been told that "air" isn't actually air... it nitrogen or something like that..due to a dirty/not treated system...

What I was told is you need to power flush, neutralise and then add inhibitor... I may be wrong though... JL is the man!!!

He is, but he appears to be absent!

I very much doubt that all the gas in the system could be nitrogen though... if it was there would be enough to run the boiler on!

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A couple of thoughts - if boiler is getting really hot its possibly steam being generated and releasing air from water, or mixing air into water (same as kettle). Flow around rest of property might be down to insufficent pipe diameter causing too much flow resitriction, hence you maybe overcompensating temperature, causing steam, causing air to be pumped into system to try and get good rad temp at end of line. I expect to be shot down by plumbing bods rapidly:^O

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A couple of thoughts - if boiler is getting really hot its possibly steam being generated and releasing air from water, or mixing air into water (same as kettle). Flow around rest of property might be down to insufficent pipe diameter causing too much flow resitriction, hence you maybe overcompensating temperature, causing steam, causing air to be pumped into system to try and get good rad temp at end of line. I expect to be shot down by plumbing bods rapidly:^O

Boiling from overheating doesn't introduce air - although yes, it would cause the expansion of any air already in the system, and yes it could create steam.

But with steam the pipes would still be hot?

It's strange that the system worked OK last year (albeit with a lot of air in!) but now it seems to be much less efficient...

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A couple of thoughts - if boiler is getting really hot its possibly steam being generated and releasing air from water, or mixing air into water (same as kettle). Flow around rest of property might be down to insufficent pipe diameter causing too much flow resitriction, hence you maybe overcompensating temperature, causing steam, causing air to be pumped into system to try and get good rad temp at end of line. I expect to be shot down by plumbing bods rapidly:^O

quickdrw.gif

:^O:^O:^O:^O:^O

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He is, but he appears to be absent!

I very much doubt that all the gas in the system could be nitrogen though... if it was there would be enough to run the boiler on!

Nitrogen is an inert gas think you mean hydrogen to run the boiler on.

Try hiring a power flushing system from HSS or the like and totally get all the c*** out of the system.

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quickdrw.gif

:^O:^O:^O:^O:^O

Like it, now where's my apprentice Tonto :^O:^O:^O

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At my brothers old house he used to get a lot of air in system. I put an automatic air vent on the towel rail in the bathroom as that was a fairly high point it seemed to help a lot. His was a pretty ancient system not sure how air got into it though.

Batty

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At my brothers old house he used to get a lot of air in system. I put an automatic air vent on the towel rail in the bathroom as that was a fairly high point it seemed to help a lot. His was a pretty ancient system not sure how air got into it though.

Batty

I might try something similar.

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Still looking for some sort of valve that could actually stop the air getting in though (if it is getting in the vent).

Do pumps ever let in air when they get old? Would that be possible?

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