Air in new central heating system.

CitizenFloor

John.G wrote:

The return from each rad should independently go to the return header, you hahe shown it in a way that all the rads in each zone are plumbed in series which I doubt very much. Edit the flow and return should be plumbed independently to the flow and return headers

Sound. That make more sense....just really trying to get a high level layout straight in my head. Anyway AVVs are open for a few days. Hopefully things clear up

rightjob!

Too long too read all that.

Have you got a back boiler and is it still connected to the system?
Its open vented,if you have no back boiler seal the system.
Air getting into the system is either a leak or else its drawing in from the vent.

CitizenFloor

It is open vented. No back boiler. There was one but it was removed.

rightjob!

CitizenFloor wrote: »

It is open vented. No back boiler. There was one but it was removed.

Change the system to sealed or semi sealed system,no need for it to be open vented.
Air is more than likely getting in from the vent.

CitizenFloor

What kind of cost would I be looking at?

CitizenFloor

I just blocked the vent temporarily....well at least for a couple of days. Right now, I can still hear some air coming out of the auto bleed valve when zones change. Maybe the zone change is causing some air to get in through the vent, with the change of pump speed. So will see if anything changes with the vent blocked for an extended period. I'd consider a sealed system as a final resort.

John.G

I know it's hard to quantify but is the venting just for a few seconds or is it more prolonged?.
What is boiler thermostat temp set at or what point on the scale if no temp indication?o

CitizenFloor

John.G wrote: »

I know it's hard to quantify but is the venting just for a few seconds or is it more prolonged?.
What is boiler thermostat temp set at or what point on the scale if no temp indication?o

Its not prolonged, unless I keep the bleed valves closed for a day or two (Which I was doing during testing) and it builds up. I have had them open for days, so lets assume there is no build up now. Every so often I hear a slight gurgle in the pipes, and if I go straight to the AVV, Ill hear air hiss out for maybe 10 or 15 seconds. Its not a whole lot of air. I think it happening when the zones change.

I just re-blocked the vent earlier, because I was standing beside the open hot press, the hot water zone closed automatically, I heard a gurgle, and then a slight hiss. Will see if the hissing persists, over the next few days.

The boiler was set to the notch, which I assume is 70. I changed it down slightly at one stage to around 65, based the example you mentioned previously. Nothing changed, so I have since changed it back to 70.

CitizenFloor

Maybe I didn't leave the vent blocked long enough the first time, or maybe there was residual air.

John.G

I would leave the vent "permanently" plugged for now. Are you fairly sure that the bung/cork or whatever is "hermetically" sealing the vent as air can get in through amazing places,
I have reattached one of your own pics of the zone vales header with the attached AAV can you tell me what the lower AAV is attached to.

CitizenFloor

John.G wrote: »

I would leave the vent "permanently" plugged for now. Are you fairly sure that the bung/cork or whatever is "hermetically" sealing the vent as air can get in through amazing places,
I have reattached one of your own pics of the zone vales header with the attached AAV can you tell me what the lower AAV is attached to.

I have a cork stuck in the vent, with insulating tape around the cork, and around the pipe. I think its sealed well enough.



Attached another pick. Its an AVV in the return from each of the zones I think?

John.G

As this (bottom) AAV is on the zones return and the pump is also on the return I would have a small concern that this might be under slight negative pressure at least some of the time.
Unscrew and remove (if you can but don't loose it) the vent blanking cap and fit a piece of plastic pipe over the vent nozzle and stick the other end into a beaker of water perched somewhere along side it and observe it from time to time and see if it sucks all the water out eventually.

CitizenFloor

John.G wrote: »

As this (bottom) AAV is on the zones return and the pump is also on the return I would have a small concern that this might be under slight negative pressure at least some of the time.
Unscrew and remove (if you can but don't loose it) the vent blanking cap and fit a piece of plastic pipe over the vent nozzle and stick the other end into a beaker of water perched somewhere along side it and observe it from time to time and see if it sucks all the water out eventually.

I am trying to think how I might do this.....looking around for a straw or something. In the meantime, I can take the cap off, put a small amount of water in the actual valve, and see what happens. Might be susceptible to evaporation though. Ill put it in and turn the valves on and off and see what happens.....

CitizenFloor

Okay, so I tested it there. The upstairs zone was on, I turned on Down and Water and there was air.

You can see the drop of water I put into the return AVV. It stays as is. I turn on the zones for down and water, and there is air in the flow AVV.

https://filebin.net/c4c7tfj6xkpiinf3/VID_20191209_214543_2.mp4?t=zygja9j8

It tapered off at the end. And the droplet of water is still on the return AVV. Ill still test it the way you mentioned when I find something to do it with.

John.G

I think that's fine, its not pulling in any air so I'd leave it open.

CitizenFloor

It seems to happen when I change a zone (Pump changes speed/Zone valve Open), and always comes out of the flow AVV.....Not sure if that can help narrow it down.......

Let me run something by you (See attached)....Is it possible at all that it could be related to that other pipe coming out of the top of the cylinder? I believe its the hot water pipe. That is vented to the attic too. And there is another pipe (the smaller one T'd off, around half way down) that is going to an old shower, which is disconnected. So essentially its going no where at all.

John.G

No, that has no connection whatsoever to the CH/HW(coil) water which is the primary water circulated around the system.

The main reason that air is vented from hot water more easily than from cooler water, a lot of AAVs are fitted right on top of the boiler or on a T piece on top of the boiler, with the PRV (safety valve) on one branch and the AAV on the other.

CitizenFloor

Okay, thanks. I had to ask.

By the way....there seems to be a lot more noise in around the water cylinder tank now, with the HW valve open. Im not sure if this is since I put the cork in the vent. Kind of sounds like there is an air lock. When I open the HW zone I can hear air moving around, when its closed I cant. Its fairly prominent.

Half considering draining the entire system at the weekend.

John.G

I think you should install a AAV on the cylinder flow just before the cylinder. Its a pity really that zone3 motorized valve wasn't installed originally where it should have been, just before the cylinder coil flow. The vent then would operate as intended under all conditions and you would have had the option of making it a combined vent/cold feed which does work very well as mine does, however you have what you have and short of converting to a fully or semi sealed system then I would suggest, as a compromise, fit that AAV at the cylinder.

Have you asked your plumber why he installed the system as is?, it sort of looked as the intention may have been to go sealed initially but didn't.

CitizenFloor

John.G wrote: »

I think you should install a AAV on the cylinder flow just before the cylinder. Its a pity really that zone3 motorized valve wasn't installed originally where it should have been, just before the cylinder coil flow. The vent then would operate as intended under all conditions and you would have had the option of making it a combined vent/cold feed which does work very well as mine does, however you have what you have and short of converting to a fully or semi sealed system then I would suggest, as a compromise, fit that AAV at the cylinder.

Have you asked your plumber why he installed the system as is?, it sort of looked as the intention may have been to go sealed initially but didn't.

I havent asked him.....Is it a big job to convert to sealed or semi sealed?

John.G

Not a big job really for a plumber but IMO a AAV will still have to be fitted close to the cylinder flow entry anyway so why not do this first and see how you get on.

CitizenFloor

John.G wrote: »

Not a big job really for a plumber but IMO a AAV will still have to be fitted close to the cylinder flow entry anyway so why not do this first and see how you get on.

Okay, I assume the various recommendations are based on the assumption that the air is getting in via the vent, which is the most likely problem.
Options are (I assume in order of cost).


1 - Move the AVV on the HW line to just before the cylinder, so when air comes in via the vent, it immediately moves out though the AVV.

2 - Move the Motorised Valve to the just before the cylinder, convert the cold feed & vents to a combined cold feed and vent, so air does not get in via the open vent.

3 - Convert to a semi sealed or fully sealed pressurised system, which should result in no air getting in.

But before all that, surely the fact that I have the vent blocked now should improve the situation as a temporary measure, before I undertake anything? I want to make absolutely sure I am fixing the correct problem i.e. the vent.

John.G

I think you would fit the AAV at the cylinder but still assume that the Vent is "permanently" blanked.

You are very wise to check out all possibilities before going sealed as I read on some other website about someone who had exhausted every possible system (apart from combined vent/feed) before he took numerous advice(s) and went fully sealed only to find that at anything approaching 70C he was getting all sorts of whoosing sounds etc especially on the hot water circuit and eventually had to settle on ~ 63C when all is quiet.
Thats why I am saying that if you go fully sealed and are still getting problems that you will have to fit that cylinder AAV anyway in a attempt to cure the problem, of course you may well find that everything will fine if you go sealed.
Another option is to contact your plumber and ask his advice and maybe come to some compromise re costs as the original install is incorrect?.

CitizenFloor

I'm certainly going to try identify the exact reason for the ingress, before making any decisions. The floors etc. are not being closed up permanently in the near future so I have time to play with.

Right now, I have the Vent blocked. I double checked it a couple of nights ago, and made sure it was airtight. It was.
I have bled the radiators and the AVV's are open etc. But I can still hear gurgling in the Hot Water Cylinder, and near the vent/cold feed area. And every so often I hear air leak out of the AVV's, usually when the motorized valves open/close.

Do you reckon draining/refilling the entire systems is a good idea? At least that way I could be relatively certain that all residual air is removed, and take it from there.

John.G

No, I wouldn't advise draining down as the whole system will then fill with air and while refilling will push most of the air out you will still have to get rid of the remainder eventually, I would only drain down if installing a AAV at the cylinder, if doing that I would leave the other two AAVs where they are as well.
If you shut off zone3 (cylinder coil) with zon1&zone2 on does the noise die down and do the AAVs still emmit air??.

Also when Zone3 is on have a look into the Feed and expansion (small) tank and see if there is any movement there and if the water is clean with no sediment in the bottom.

CitizenFloor

John.G wrote: »

No, I wouldn't advise draining down as the whole system will then fill with air and while refilling will push most of the air out you will still have to get rid of the remainder eventually, I would only drain down if installing a AAV at the cylinder, if doing that I would leave the other two AAVs where they are as well.

Fair enough. Ill leave it as is, and try expel the air, with the vent blocked, like I am doing now.

John.G wrote: »

If you shut off zone3 (cylinder coil) with zon1&zone2 on does the noise die down and do the AAVs still emmit air??.

It does die down (Air coming out of AVV, and Gurgling). The gurgling seems to be originating in/near the HW cylinder, and in near the two T's for the cold feed & Flow with vent. But I cant pin point it.

John.G wrote: »

Also when Zone3 is on have a look into the Feed and expansion (small) tank and see if there is any movement there and if the water is clean with no sediment in the bottom.

I dont think the cold feed is blocked. The small tank in the attic is crystal clear. I will check for movement later though as suggested.

Tnx.

John.G

Just wondering if the cause of that noise just possibly might be the "semi trapped" water in the corked vent.

Probably impossible to get hold of a plumber at this time of year and don't know if you or someone in your house are handy but it should be very easy to drain the water down below the level of water in the T, pipe 2, where it branches off to the cylinder, (I assume this T is above the level of the bedroom radiator tops), First isolate the boiler then just tie up the small tank ballcock and bail or syphon out the few litres of water, then slacken off the pipe at the T going to the cylinder and drain off the water, there should only be a litre or so, re tighten this and then remove the vent pipe and install the Air vent here (rather than at the cylinder, you can always shift it there later if required). and refill your tank, tempting??.

CitizenFloor

John.G wrote: »

Just wondering if the cause of that noise just possibly might be the "semi trapped" water in the corked vent.

I was thinking the same thing....suction might be keeping it in place, without the vent being open at the top.....It sounds (at least to my non-plumber ears :pac: ) that that might be happening.....like a slurping sound.

John.G wrote: »

Probably impossible to get hold of a plumber at this time of year and don't know if you or someone in your house are handy but it should be very easy to drain the water down below the level of water in the T, pipe 2, where it branches off to the cylinder, (I assume this T is above the level of the bedroom radiator tops), First isolate the boiler then just tie up the small tank ballcock and bail or syphon out the few litres of water, then slacken off the pipe at the T going to the cylinder and drain off the water, there should only be a litre or so, re tighten this and then remove the vent pipe and install the Air vent here (rather than at the cylinder, you can always shift it there later if required). and refill your tank, tempting??.

Not sure about the height of the T, I think it is higher than the rads, Ill check.

The idea sounds doable over a weekend. But I can get a plumber which is a much preferred option!

But, just so I am clear, are you suggesting completely removing the vent and replacing with an AVV? Is this where I need to check if the cold feed is large enough to act as the expansion. I think that is happening now, as the cold feed gets warm about half way up, in the current set-up, when everything is hot (All zones, HW etc.). You mentioned checking that with the plumber recently.

I like that option....Its less messy, it cuts out the vent (which may be causing the ingress), and helps release whatever air problem is in there now/in future.

John.G

Yes, that's what I'm suggesting, it can always be reversed very easily.
The cold feed is certainly large enough to take the expansion as the vent pipe only expands probably ~ 0.25 litres or so.
If you are getting a plumber in, I really don't know if it would be better to fit the AAV at the cylinder (end) or not, if doing it yourself I would certainly just fit it at the T.

Its quite a relatively cheap option and won't break the bank if it doesn't work out.

CitizenFloor

Its been a while!

I had just left everything as is for a month plus. The two automatic bleed valves were open. Yesterday, I bled the radiator closest to the valves upstairs for the first time in a month, and air came out for a good 6 seconds. I hadn't noticed any issues with the rad, so I was not expecting so much air.

In relation to the proposed location of the new bleed valve.....The T would be under the height of the top of the rads upstairs. I assume it would need to be at a high point, or at least higher than the top of the rads.

I also found a leak directly under the three zone valves today. Its on the return part of the system. The leak was over the chimney breast, so I didn't notice it, until some black mold started to form at the top of the breast, where the chimney meets the ceiling. I pulled down the ceiling (which I intended on doing this week anyway), and fixed the leak. Pic attached...I wonder if that could be the cause of the ingress.

Back to testing :P

My plumber is coming in a couple of weeks, for another job. Ill get him to change the system to sealed if all else fails.