Air being vented into Open Vented CH system, advice

[rrwfotr]

Hi all I have a open vented central heating system, a few weeks ago I noticed after replacing my Grundfos 15/50 pump to a 15/60 pump (to get more water pressure to pump around house have quite a few double skinned rads) that in my bathroom air was getting collected every day in the rad.

I went into the loft and discovered that air was being drawn into the system by the vent pipe when the pump was on setting two when I set on setting one there appears to be no air being drawn into the system.

My question is if I want to increase pumping pressure on my central heating system and want to place it on setting two or three into the system how can I stop air being drawn into the system ? Is there any devise I can attach to the end of the vent pipe in the f/e tank to allow venting from the system but not allow air into the system, any advice would be most appreciated as you can imagine I don’t want air in my system.

 

[muggles]

OK idiot's question first...are you sure you put the new pump in the same way round as the old one? The label on the head does not indicate that it's the same way up, the arrow on the body (the rear part) does. If you've put it in upside down then this may well be the problem.

Failing that, you may need to reposition where your feed and/or vent connects into your system.

 

[ScottCheg]

No. If air is sucking in you have a corrosion problem. The neutral point on the system has been compromised.

I'm in a 4 bed town house and have a 15-50 on speed 2. (14 rads).

Careful balancing and a system working correctly is all thats required.

Scott.

 

[muggles]

No. If air is sucking in you have a corrosion problem.

Rubbish. Although over time the air that's being sucked in by the pump will cause corrosion, it's not corrosion causing air to be sucked in. The problem only happens when the pump is on higher speed settings and didn't happen when he had the old pump. Surely you're not suggesting that changing the pump has suddenly caused corrosion?!

 

[rrwfotr]

OK idiot's question first...are you sure you put the new pump in the same way round as the old one? The label on the head does not indicate that it's the same way up, the arrow on the body (the rear part) does. If you've put it in upside down then this may well be the problem.

Failing that, you may need to reposition where your feed and/or vent connects into your system.

Yep postioned pump in same postion as before. The air being drawn into system when placed on setting 2 on higher rated pumo 15/60 the previous punp 15/15 on setting two did not vent as much air I only bled the bathroom rad once every winter with the new pump it's needs bleeding every day

Is there not device I can place /add on the vent pipe as its just a open pipe at the moment in the top of f/e tank if I want to place the new pump on setting two? Thanks in advance.

 

[qplumb2010]

problem with the way the feed and vent pipe are plumbed in then or postion of pump - or your pump is just too strong on setting 2 - what was the reason for the added pump pressure ? cold rads ??

 

[rrwfotr]

problem with the way the feed and vent pipe are plumbed in then or postion of pump - or your pump is just too strong on setting 2 - what was the reason for the added pump pressure ? cold rads ??

I think the pipe work is ok just the pump is two strong on setting two for 15/60 pump.

The reason why I added the bigger pump was that I have two rooms that have quite large double skinned rads and they only warm up half way the bottoms are cold so wanted a bigger pump to warm the bottoms this has inproved the situation silghtly. The house is a large house with loads of pipe work running along the house approx 20 metres in length side of house.

 

[TicklyT]

Back to qplumb's question - where do the feed and vent pipes connect to the system?

Incorrectly positioned feed and vent pipes tend to draw air into the system, or lead to pumping over.

Entrained air leads to corrosion.

Corrosion leads to sludge.

Sludge forms partial blockages.

Partial blockages lead to poor circulation.

Attempts to improve the circulation without correcting the feed and vent positions draws more air into the system.

And off round the loop we go again.

 

[muggles]

Definitely a problem with the way the feed and vent to your F+E tank in your loft are plumbed in I'd say, they're connected in the wrong place in relation to your pump and this is why air is being drawn in, so you'll have to move them if you want to cure it

 

[rrwfotr]

The pipework appears to be bog standard, the feed into the system is in the loft connected to the f/e tank. The vent is connented to the hot water cylinder and feed pipe below the f/e tank. directly below in the airing cubard.

Just find it stange that setting one on pump appears to draw no air in but higher seting it starts drawing air in. Reading other posts, would a automatic air vent connected to vent in f/e tank cure this situaton i.e allow venting from hot water cylinder and stop air getting air into ch system via increased pump pressure? Thanks in advance.

 

[muggles]

Unless you have a primatic cylinder, your hot water cylinder is irrelevant here.

How many loft tanks do you have? If it's two (most houses have two) then you have a normal cylinder and seperate vents for the heating and hot water, the vent coming off the top of the hot water cylinder is not the one you're getting a problem with.

You're getting air drawn into the system at higher pump settings because your vent is almost certainly connected in the wrong place, as has already been stated. I think I'm right in saying that we all suspect that your vent is on the negative pressure side of your pump, so increasing the speed increases the negative pressure (or pull) and pulls air down the vent into your system. The more power the pump is given, the more air is drawn in. On the low setting there's probably not enough power in the pump to draw the air in.

An automatic air vent will do absolutely nothing to help; they allow air in as well as out and as the problem is that air is being sucked in this will cure nothing. Do not put anything on your open vent pipes at all, they must be just that, open. No valves, no fancy gadgets, nothing. You need to reposition your feed/vent pipework, that's all.

A photograph of the pipework in your airing cupboard may help to explain things...

 

[rrwfotr]

muggles I think your right, then vent appears to be connected on the negative pressure side, what do you think guys. Thanks in advance.

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[sloppytom]

that is a air separator designed to remove air particals. corrosion ans sludge from system maybe blocking cold feed. how high is tank in loft in relation to air sep and pump. u need a good height to give the neutral point

 

[rrwfotr]

that is a air separator designed to remove air particals. corrosion ans sludge from system maybe blocking cold feed.

I dont think the cold feed is blocked as I drained down the f/e tank t and refilled a month ago when I changed punp and the pressure was ok when I opened pump vale. The height is around 2 -3 metres, the air vent slopes up an over and bends in the f/e tank.

 

[sloppytom]

what about the height of up F and E tank, the height shud be in relation to pump power