pump positioning

[kev999]

Hi all,

I'm getting air in my vented central heating system. Pumping over seemed likely as there wasn't much head, so I raised the header tank to just under the roof tiles and achieved a static head of about 1m or so - I can't detect any pumping over now. I also did a thorough cleaning and boiler descale with DS-40 and all seems to flow very nicely - the once kettling boiler is silent too!

But the air continues to get in , at least i think so as its been a few weeks now so presumably its unlikely to be still coming out after the last fill? Its particularly annoying at start-up because the pump is at the highest part of the system and the air accumulates up there making it very noisy until its dispersed and/or bubbled into the rads instead.

So I'm wondering:
- Is 1m still likely to be an insufficient head?
- Can pump/flow turbulence cause air to be created (the pump has a 22mm elbow just after it, and there is also one close to the inlet side too, just before the vent and feed pipes, which probably isn't great)?
- The pump manual advises >1.5m head, and as its near the top of the system it hasn't quite got that - it seems to bleed okay but could this still be a factor?
- I notice that air seems to also accumulate in the pipe from the peggler automatic bypass valve, and gets flushed out into the rest of the system when this starts to bypass. Is it likely that either the valve itself or the shield valve after it could be introducing air?
- What else am i missing?

I'm getting close to ripping out the airing cupboard and re-doing it with a vertically orientated pump and no tight bends, but that would be a lot of plumbing and wall-plastering etc so it would be very sad if it still didn't work or wasn't even necessary. Any thoughts would be much appreciated

Cheers
kev

 

[Winston]

What about fitting a automatic air vent, I had similar problems since I have done mine its been perfect.

 

[Puddle]

This sometimes happens if there is a small leak just before the pump,not small enough to leak water put enough for air to be sucked in when pump on,this could have been exposed by chemical flush,you could try tightening up joints ,this could cause more problems ,first get some silicon and smear neatly around pump unions and compresion joints near pump,just apply light covering ,like you were applying cream to your skin,if this works then you can leave or decide to drain and remake joints
Also see if you can turn pump speed down and still achieve required operation

 

[kev999]

Hi, thanks for the suggestions!

I'll try tightening my pump nuts etc tonight - I did try some external sealer but maybe I'll have a more thorough go with that too.

I briefly ran the pump more slowly but didn't stay with it as it was having more trouble getting the air down into the rads. However i take your point; if it is in some way contributing to the air getting in then maybe I should give it more time and see if it slowly gets better. I have to say its not a well designed system, the pump sits horizontally at the very top of the upstairs ceiling (the airing cupboard is over the stairs) and there are quite a few elbows because its so cramped up there.

Winston, what sort of automatic vent worked for you - was it an air separator or something like that? If i can't cure it then getting rid of the symptoms may be almost as good.

Cheers,
Kev

 

[Winston]

Kev999 just go to a merchant mate and get a automatic air vent, you can get ones that you can do manually but I shy away from them just in case a customer attempts to do it themselves and can get scolded. There cheap to about £7 + vodka & tonic.

Cant think of the name of the manufactuer will have a look in my van.

 

[kev999]

Kev999 just go to a merchant mate and get a automatic air vent, you can get ones that you can do manually but I shy away from them just in case a customer attempts to do it themselves and can get scolded. There cheap to about £7 + vodka & tonic.

Cant think of the name of the manufactuer will have a look in my van.

Thanks - thats just what I was after!

I've posted another thread about the feed and expansion pipe positions just in case I'm overlooking something stupid, but I think its okay (except for maybe the head, and i can't do much about that) so the automatic vent sounds perfect. I originally had the idea that I should stop the air at source, but I've been piddling around with it for ages without finding what that is - guess its time to just sort it with this bit of kit and stop worrying!

Thanks again,
Kev

 

[leakylea]

could you have a leak, water out = air in

 

[Winston]

Automatic air vent is made by CALEFFI on the box says ROBOCAL you will need to position at a high point with a tee and bit of pipe, and you still have to bleed your rads on filling up. But as leakylee said have you got a leak? normally though your boiler would over heat. But listen to the guys here I am new but hope all goes well.

 

[kev999]

Automatic air vent is made by CALEFFI on the box says ROBOCAL you will need to position at a high point with a tee and bit of pipe, and you still have to bleed your rads on filling up. But as leakylee said have you got a leak? normally though your boiler would over heat. But listen to the guys here I am new but hope all goes well.

Cheers for that, I'll look it up

Kev

could you have a leak, water out = air in

Hi, Thanks for the suggestion. I don't think I have a leak though; I was very cautious a while ago when I had the acid cleaner in and checked everything visible whenever possible (nothing damp looking on the ceilings etc either). Also the feed/expansion tank doesn't seem to be emptying/filling and the inhibitor doesn't look like its being diluted or anything. Guess time may tell though, I'll keep my eyes open!

Thanks
Kev