Air in heating system

[Schmill]

Ok, so I've been having a nightmare with 'air' in the heating system and also pumping-over.

Originally the pipe layout was like this;

Old Pipe Layout

• Schmill
• 28 Mar 2011
• 3

Boilerflow coming up the left hand side, vent pipe to the loft continuing up, the main flow turning horizontal. Then a T to the 15mm feed, and then carrying on down to the pump.

With this arrangement I was unable to fill the system at a point in the past as the feed had blocked. Also as the short horizontal section of feed pipe just after the T wasn't quite horizontal it seemed quite common to get an airlock in there

I then changed the top half of the loop and re-ran the feed as this;

Top of Heating Pipe Work

• Schmill
• 7 Apr 2011
• 3

Changing the feed to an angled section of pipe has removed the problem of getting airlocks in the feed, but I still get air bubbling UP the feed rather than the vent, and also (I think) am getting air sucked into the system via the vent pipe

As a final attempt I am planning to change it again, incorporating some 'features' that I have seen used elsewhere.
Comments please on whether ( a ) you'd expect it to fix the problems, and ( b ) whether you would do anything differently;

Proposed Vent / Feed Layout

• Schmill
• 21 Jun 2011
• 1

I believe that;

- Taking the VENT from the horizontal section rather than from the vertical 'straight-on' route that it currently is should help to stop the water pumping over into the F/E tank in the loft.

- Having an inverted loop in the feed pipe should stop air trying to travel up this pipe to get out of the system, whilst still allowing the feed to operate correctly. I would imagine that this 'might' be more suseptible to blockages, but if I keep the system clean, and perhaps do the loop with compression fittings to allow removal if need be it shouldn't be too much of an issue?

In addition to the above, is it advisable to fit an air seperator such as this;

I have heard that they too can be prone to blocking though?
If it is advisable to fit one, please advise which way to fit it! I would think that the feed from the boiler would enter at the side on the highest point, and then exit from the lower point which should be clear of air? (the air bubbling out through the vertical port), but I might have the entry and exit the wrong way around for reasons I cannot think of?

Lastly, if it is advised to fit an air seperator would a better solution be to fit one like this, which includes the cold feed connection point;

Not that I can really see a benfit to that, other than it saves using a seperate T after the seperator?

Many many thanks!

 

[mickyg]

what boiler do you have? if it allows it i would combine the cold feed and open vent.

 

[Schmill]

The boiler is a 'British Gas' Ideal RD2 450.

No idea at all if it supports / allows combined Vent & feed.

Q1 ) What is it about a boiler that determines this?

Q2 ) What is the benefit of a combined vent & feed?

Q3 ) How do you plumb that? I'm guessing it would just be a single pipe from either where the vent is currently, or else moved to the horizontal section, and I'm guessing that at some point it still has to split into seperate feed & vent pipes, but where and how I don't know.

Thanks

 

[Andygasman2010]

As Mickyg suggested, combined is probably the best way to go.

Your boiler has an overheat stat so this is allowed, if it didn't then it would need a vent incase the boiler stat failed and it started to boil.

I can't explain propperly why no vent is best but I think it's to do with positive/negative pressures. Plus if there's no vent, air can't be sucked in through it! One of the other guys will give a better explanation of this, i'm sure

To be honest, the way you have it piped up shuold work fine... maybe you have a blockage further along the pipe?

To combine it you need to tee the feed into the vent pipe.

Oh... an obvious one just incase, your pump should be pumping downward based on your pictures.

 

[45yearsagasman]

View media item 29821That'll work but make sure all the surrounding pipe is clear. You can use the air sep but don't bother with the cold feed type.

 

[Schmill]

So basically I end up with a 22mm pipe from the F/E tank T-ed into the system and that's it... ?

Certainly seems more straight forward, and I can definitly see how it wouldn't let any air into the system.
I presume the air coming out of the system, and the water going into a system can 'pass' each other in the combined pipe without problems?

What isn't clear to me is why it wouldn't be done this way all the time?
I mean even if the boiler did start to boil, surely the air / steam(?) produced would still work its way up the fill/vent pipe combo and just bubble out through the F/E tank ?

 

[45yearsagasman]

I cannot think why this was never adopted from the word go. It is however only permitted on systems where the boiler has overheat protection, and yours is suitable. I emphasise the need for the surrounding pipework to be clear. It's impossible for air to be drawn in and air bubbles will go up the fill/vent pipe. Fitting an air sep will help but is not mandatory.