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Been messing with my central heating over the last week or so, replacing some existing rads and also adding a couple of new ones.

Anyway this has shown that the c/heating is a pig to bleed, and by this I mean getting the pump primed and bled and pumping water around.

The diagram below is current setup, all this is in the loft, the boiler is downstairs.



Now to me, the air bleed loop into the top of the header, being combined with the cold gravity feed is the problem. Trapped air gets in the pipe, but the weight of the head means it gets stuck there and cannot vent.

I am considering a simple mod to make it like so,



The question is, does anyone think this will make a toss of difference, or is it a waste of time?

thats how it should be tom like you say the air cant vent you should be fine with that mod.

Edited by wng691s clubby on 16th Nov, 2011.

Done now needs redoing lol

prob done this tom but , has the pump itself got a bleed on it ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

if its simular to this you just undo the the big screw a little until it stops hissing

Done now needs redoing lol

The conventional way is to take the cold feed (the one you've labelled as Water Head) to the cold side of the boiler, ideally as close as possible to the boiler, but if you want to minimise the run, it could go into the return from the HW tank (bottom left of your sketch).

Schrödinger's cat - so which one am I ???

Gents

Yes I've been bleeding the pump, but you only get a small amount of air out and then water.
Run it and stop it, lots of gurgling then some more air.

Was fecking about with it for over an hour last night just to get the pump to run without airlocking after 30 sec running. Eventually got to the stage where it is running although noisy with air circulating.

I'm going to give my mod a try, perhaps your idea is a better one Rod with where to introduce it. However some internet pictures show and state that the cold feed should be as close as poss to the expansion.

Could the pump actually be drawing air in through the vent?

If you have fitted thermostatic rad valves and it's not too cold, then the pump will cause a reduced pressure on the suction side.

Try it with all the rads turn up a bit.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I don't think it is Paul although theory works.

The only time I have problems is after I've dumped it to do some work. In 6 yr in the house I've dumped it 5 times, 4 of those times in the last week, hence now thinking about sorting it!

Once you have bled it, it does not need it again, its just a pig to do from dry.

Also the rad in the bathroom is not on a TRV, so there is always a flow path.

pull all the TRVs off the valves to make sure they are not causing an issue; I had this with part of the circuit in the 1st floor and it turned out to be a faulty trv

after a fresh refill it takes a couple of days to get all the air out beacause of the amount of oxygen molecules in the fresh water, normally your heating water is kind of stagnent, but doing your mod will make it easyer to get rid of the enitial large amouts of air and stop the gargling but youll need to nip around the rads a few time to get rid of the little bits left

Done now needs redoing lol

Edited by Rod S on 16th Nov, 2011.

Schrödinger's cat - so which one am I ???

Tom. Have u got an a jet? Looks like a little cyinder with 2 pipes from above and 2 from below and 1 of those wil go into the pump. It will be in the airing cubard

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Tom. Have u got an a jet? Looks like a little cyinder with 2 pipes from above and 2 from below and 1 of those wil go into the pump. It will be in the airing cubard

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

we were right in the middle of doing the same to our new house Tom new rads moving others ect and we have what looks like the identical setup, not in a position to re-fill and bleed my sysstem yet

the separate vent and feed pipe is allways the better option so change it if you need to, make sure there before the pump and that there is not any sort of airjet. if there is remove it else ull have problems.

also try and fit an automatic air vent, often off the feed into the coil on the cyclinder.

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Any joy with this Tom or is it a job for the weekend

Done now needs redoing lol

I designed and installed the system here, 2 heat sources, 3 pumps, 4 zones and 20 rads.

I've only got a single 22mm link to the header tank with no air breather at all. I've drained and re-filled a few times without issue, so not sure if that is the problem.

One thing that I would recommend and that is fitting maintenance valves. These days if I need to change anything, i just isolate and drain part of the system. When the work is done, I just crack the 'in' maintenance valve, open the radiator bleed valves and let it fill slowly. No problems with air, other than the usual need for the occaisional bleed.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul the 1 thing to watch out for is old maintenance valves like to leak when they get used.

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Tom if you would like me to call take a look give me a pm with your mobile number
I might be able to help I'll call on my way home. free

Craig

Craig

my mini van http://www.turbominis.co.uk/forums/index.php?p=vt&tid=448248

now theres an offer tom get the kettle on

As eden say above, if that lot is in the loft and the highest rads are in the rooms below, then the top line into the cylinder/3 port valve/flow to rads is the top part of the system and should have a means to vent usually either manual or an auto air vent, an airlock anywhere in the system causes much the same problems and the pump generally wont shift it in an open vent system. From as you describe when all started up the pump runs and is generally noisy, bleed the pump and it all quietens down and then after seconds/mins the pump speed/noise picks up and makes the noises you descibe-open vent microbore systems are a twat for it

Wether there is a single vent/feed pipe or separate as per the 2 drawings that is the safety vent-not the air vent for the whole system, either there has to be auto/manual air vents at the highest parts or some sort of air separator such as the aerjec mentioned, all that does is manifold the main boiler flow into the open vent and allows it to perform as the full system vent

A photo of the cylinder set up would be a big help. Hope you get it sorted

ta

oli

Edited by oli79 on 17th Nov, 2011.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Topic resurection.

After have some minor trouble this week with our central heating, I finally have had it with air (non condensables) rattling round the pipes, and remembered this topic.

I have considered fitting an automatic air vent, but then thought why the original vent was not working as it should.

Reading the Grundfoss UPS 15-50 pump instalation guide, it suggests the pump must be installed in a vertical pipe run in the flow from the boiler, flow direction upwards. The guide suggests that mounting the pump with flow direction downards, is not recomended (as it is installed in our house) unless an effective air purger and vent is incorporated in the system (which it isn't). Typically the builders have not fitted an essential component to ensure adequate venting, a part that only costs £10 (would have been about £5 ten years ago) http://www.heatingcontrolsonline.co.uk/tow...ator-p-267.html



Sooooo, at that price, i'm going to fit one and see how it performs.

Diagram of current air vent and suggested air separator installation.

Attachments:

29.77kb

Edited by Sprocket on 10th Dec, 2011.

Sproket dont fit 1! There useliss.

I had to rip 1 out on friday as I. Had caused the cold feed to scale over solid. So it wuldent fill

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Not sure how adding a slightly larger 'chamber' to an already existing similarly piped layout can cause the cold water feed to scale over If that is the case, then the cold feed as it is now would scale over anyway? I'm not altering the cold feed pipework, just replacing the tee on the flow/ vent pipe.

I can see how it works, as the clod feed/ flow is lower than the top of the chamber. as areated water enters the chamber, it's velocity slows down a little, giving the air bubbles time to rise. as they rise, they cannot enter the flow to the pump which is at the bottom. The cold water feed works exactly the same as it always has.

Asloforgot to say, looking at the pipe inlet and outlet configuration, it is actually a swirl pot, similar to what some use on there cooling system on their car.

Edited by Sprocket on 11th Dec, 2011.

I know wat ur saying mate and I agree, but I rip them out time after time because they cause problems.
Wat exactly is ur problem?

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!