Air in new central heating system.

CitizenFloor

I recently had a completely new central heating system installed (New Rads, Flexible Piping, Boiler etc.). Its not a pressurized system. I have noticed that two rads upstairs need to bled every 2 or 3 days. Quite a bit of air is getting in. Its a zoned system and there are two automatic bleed valves installed. https://en.wikipedia.org/wiki/Automatic_bleeding_valve



I called my plumber who installed the system, he said just to leave the two valves open all the time. That is fair enough, but my issue is that there is air getting in somewhere, and that problem needs to be fixed.



Am I correct to assume the issue should be fixed, and the valves should be there are a backup?

CitizenFloor

If I am correct in my assumption that the auto bleed valves are really there as a secondary measure, can anyone suggest a method of finding where the air might be getting in? I can hear a very small amount of air consistently coming out of the bleed valves.

All my floors, are opened, and I have access to the joints in the pipes. I might try going around and tightening the intersections in the piping to see is the air stops.

If anyone has a better idea, would be appreciated.

John.G

CitizenFloor wrote: »

I recently had a completely new central heating system installed (New Rads, Flexible Piping, Boiler etc.). Its not a pressurized system. I have noticed that two rads upstairs need to bled every 2 or 3 days. Quite a bit of air is getting in. Its a zoned system and there are two automatic bleed valves installed. https://en.wikipedia.org/wiki/Automatic_bleeding_valve



I called my plumber who installed the system, he said just to leave the two valves open all the time. That is fair enough, but my issue is that there is air getting in somewhere, and that problem needs to be fixed.



Am I correct to assume the issue should be fixed, and the valves should be there are a backup?

Its a bit unusual these days to have a completely new system installed unvented, with a Feed & Expansion tank overhead. If not installed correctly it could be drawing air in through the vent pipe. The "accepted" way of doing this now is that the circulating pump is installed on the flow line from the boiler and
FROM the boiler the order is vent....cold feed....pump with the cold feed as close to the pump (suction) as possible and no more than 150MM between the vent and cold feed OR (assuming system not solid fuel) a combined cold feed and vent (like my 47 year old system). To see if air is being drawn in you can just fill a plastic bag with water and hold it with the vent pipe immersed in the water and get someone to stop/start the boiler/pump and see if any sign of movement in the bag. Re auto air vents, there are or should be caps on them that you can screw shut, or there may be isolating valves, I'd advise to leave these open initially and when all the air has been expelled, shut them and occasionally re open them to check for air.
Do you have a oil or gas boiler and is the circulating pump external and if so is it fitted on the Boiler Flow or Return? (mine is on the return) my vent pipe is a continuation of the 3/4 ins flow to the cylinder coil and is teed into the cold feed where it passes up very (very) close to the feed and expansion tank.

Something else you could try, if the boiler setpoint is ~ 70/75C reduce it to 60/65C and see if air ingress or whatever stops. I read a post somewhere by someone who had installed a new boiler in a vented system that had run perfectly for years, he just couldn't get rid of the air after installing the new (gas) boiler so he changed the system to a unvented (pressurised) system and still got exactly the same problem which would then disappear if he reduced the boiler setpoint to 60/65c but would return as soon as he increased back up to > 70C. At the time of writing he still hasn't sorted it out, some "experts" say it points to a boiler heat exchanger problem.

CitizenFloor

Thanks John....

I appreciate the details response. Where exactly would the vent pipe be located?...in the attic, or in the shed near the boiler. I am not sure what I am looking for.

Its an oil condenser boiler, and the pump is fitted in the boiler house. Ill check whether the pump is fitted on the flow or return when I get home.

John.G

The vent should carry on up over (like a walking stick) the smaller of two tanks fitted in your attic. Are you sure it's a un pressurised system? and is it a gas or oil fired boiler?.

You said above its a oil fired boiler

CitizenFloor

Its an oil fired condenser boiler. There is 3 tanks in the attic, 2 large and 1 small.

I was reading about the vent maybe sucking in air, but was not sure where to check. I think I know the pipe you are talking about, but Ill upload a picture to confirm later.

John.G

As well as checking this and the position of the circulating pump you might also check where the cold feed is teed into the system, this will be a another (smaller bore) pipe coming out of the bottom of this small tank, if its teed into the vent (like mine) then its very unlikely that you will get any air ingress through here.

CitizenFloor

So, I took pictures of the boiler and the pump. I think the pump is on the return. The line without the pump has FL written on it, and its hotter. I assume that is the line just coming out of the boiler.

The other pictures are the tank in the attic. Is the vent pipe the one pointing down into the small tank?
I should immerse that in water and look for movement?

John.G

That's it, yes. Switch off the boiler and fill a clear plastic bag with water and tie wrap it or use insulation tape to secure it to the vent pipe with the end of the vent pipe immersed in the "bag of water" then get somebody to restart the pump while you are watching it and see if there is any change/movement in the water level, then watch it again and get someone to switch off the boiler and check again for any movement.

Later on you might try and see if that vent pipe is a continuation of the hot water cylinder heating coil (top) and try and see where the cold feed (coming out of the small tank end), is connected.

One other very important item is the pump speed setting, too high a setting can cause problems, please post a close up photo of the pump label or write down the details from it.

CitizenFloor

The pump is on auto.....about 5W. There are other settings. (I, II, III, PP2, PP1, CP2, CP1, and a Moon & Stars Symbol). All the other settings result in it going higher than 5w, up to around 11, 12. I was told to leave it on auto initially. I turned it onto the highest setting earlier to test, and water started coming out of the vent pipe if that makes sense? It was obviously too high....

One thing I noticed, the air seems to be coming out of the bleed valves more, when the boiler is firing. Does that point to anything? The pump is constantly ticking over. But when the boiler is on, I can hear the more air.

The vent pipe comes down into the hot press, and is T'd off and connects to the middle of the water cylinder.

Pics attached.

Would moving the pump to the flow potentially fix the issue?

John.G

Firstly take the pump (Tuscon?) night control off, I think you just press the "moon button" then see what the power settles at in "Auto", 5W is completely useless IMO. If it settles at ~ 14/20W in auto mode then not too bad but Auto operation in any of these smart pumps just does not seem to work well although I do know of one case with your pump where it worked quite well at ~ 16/20W but with night mode off. the highest fixed speed setting of 3 is definitely too high, I would suggest fixed speed 2 which is 3.2 M and while a bit "weak" maybe might work quite well if your system is a low loss system. Theoretically, I would think that a PP2 setting will/should give the best results, just check for no vent pump over on this setting, if you do get pump over, run on fixed speed 2 and check again. You might post the power in both cases and if PP2 gives 14/20W then the circulation rate should, again, IMO, be pretty good.
However, pump over should not occur under any/most conditions so when you get a chance you might trace it and see where the cold feed connects into the system. You certainly should not have to reposition the pump but may opt to convert to the combined cold feed and vent like mine but I wouldn.t panic just yet.

CitizenFloor

It is a Tucson...."PP2" gives only 7w....

"CP1" gives 10w, and setting "I" gives 13w. Setting "II" goes to 24w...assuming I should leave it at setting "I" & 13w. There does not appear to be pump over. Will a faster flow potentially fix the air ingress?

Bit of a remedial question, but where should I expect the cold feed to connect to the system? Where would it be connected to/from? Trying to wrap my head around it....

John.G

Will get back re pump settings but I'm a bit puzzled re the position of the hot water cylinder zone valve 3 which is taken off the hot water manifold, now if this is the pipe that continues on as the vent (near your hand in photo) it will (vent) be blanked off when the zone valve is closed? it (zone v/v) should be located on the branch to the right of your finger into the hot water cylinder coil., you might check this out again. Re cold water feed, this might join the return from the cylinder coil but would need to be traced out. Will repost shortly.

Is that Teed off pipe (near hand) coming out of the bottom of the cylinder coil or is it going into the top of the coil??. Also is the black marker on the vertical 3/4 ins pipe an arrow and if so what way is it pointing?.

Re pump settings: what was the pump power in Auto with the night mode off??. looking at your figures I would say that fixed speed II setting is the best as long as no pump over but if pump over leave on speed setting I.

CitizenFloor

Let me try to explain the layout better.

I'm not sure if this is relevant, but there are three tanks in the attic. One large one which I would describe as the standard cold water tank.

Then the small tank with with the vent pipe going into it, and another large tank beside that (Both pictured), with what looks like a vent pipe going into it too.

In pic 1, you can see 5 pipes.

1 - A pipe coming out of the bottom of the small tank via a hole in the side
2 - The vent pipe for the small tank - You can see it bend back over into the tank.
3 - A pipe that appears to be going into the bottom of the large tank.
4 - Appears to be a vent for the large tank.
5 - Appears to be going into the bottom of the large tank also.

In pic 2, you can see the 5 pipe down in the hot-press (Don't count the two on the very left, as they are for a future shower, not connected)

In pictures 2 & 3, you can see that pipe 2 (the small tank vent) is T'd off to the middle of the cylinder.

Pipe 4 the large tank vent, is T'd off to the top of the cylinder.

Its not an arrow, its "FL" for flow.

Does that make more sense?

John.G

Forget about any vent(s) coming off the TOP of the cylinder, I am only interested in the primary
(boiler) water vent.
If you look at the cylinder SIDES, you will see one pipe not too far from the top but still on the cylinder side, this is the boiler water flow into the cylinder coil, it then flows downwards through the coil and exits further down but nearer the bottom still on the side, I only want to know if the zone valve is feeding this top coil entry and if it is how does the vent work?. Maybe tomorrow when the zone valve for the hot water heating has been off for sometime, get somebody to open it and whichever3/4 ins pipe gets hot first is the flow to the coil and IF the vent to the small tank is a continuation of this then it is wrong so you will have to be happy that its not done this way and that there is a un interrupted open vent at all times irrespective of zone valve positions.

John.G

OK I'm back to the drawing board, is the highlighted vertical pipe the vent that goes over the small tank and is the highlighted smaller pipe that goes off to the right the feed into the cylinder centre, if so just see if its going into the coil top at the side. As I said above when the hot water zone valve is opened see does this vertical pipe and T off to the right, get hot.

CitizenFloor

It is the vent pipe, it does go to feed the cylinder around half way down, and it does get hot when the water is turned on.

John.G

Thanks, well it doesn't seem to have been properly installed as the way I see it is that the vent is effectively blanked off when the hot water cylinder zone valve is shut, I assume you havn't got another heating source solid fuel? I enclose a photo of my hotwater zone valve which is (properly) installed on the T into the cylinder coil.(Rotate the picture 90 deg)

CitizenFloor

That is disappointing to hear....There was an open fire with back boiler, but that has been cut out of the circuit.

So, just so I understand, are you saying that this is the cause of the air ingress, or is that just another issue?

And is the other vent pipe not relevant? The fourth pipe here is also vented to the big tank.

And probably most important, is it a big deal to fix?

John.G

Any gravity fed hot water cylinder will also have a vent from the very top of the cylinder as your's has, Its possible that a separate boiler vent has been run and is vented into one of the bigger tanks but it would be unusual (and a waste of piping) but not impossible as you seem to have a extra vent for some reason or other. Its possible that he used the old back boiler flow pipe as a separate vent but into one of the big tanks for one reason or another. I assume the two larger tanks are both Cold water storage tanks using two to give increased capacity.
Re "blanked" vent causing air ingress, I just don't know (I have never experienced it before) as expansion will still take place back up the cold water feed and you have automatic air vents installed. What you may try to prove/disprove this is to heat up your cylinder as per normal then programme it to remain off, then open its zone valve manually and latch it open while you are running the test and run the other two zones for a number of hours with auto air vents open and see does the noise die down after a few hours, if no vent pump over run on fixed speed 2 and see how you get on, you could run for a few days this way but remember the hot water cylinder will eventually heat up to near boiler setpoint temperature which may not be a good idea if small children in the house.

Have you any idea where the cold feed is teed in to the system?.

The fix, I would contact the plumber and politely ask him how the boiler is vented, he seems to have done a excellent plumbing job so I don't think he would take umbrage as he may have a perfectly good explanation re the venting and if he hasn,t, he will fix it.

CitizenFloor

I appreciate all the responses, John. Ill be doing some more testing later, when I get home.

I'll check for the cold feed too. Apologies in advance for another remedial question...I assume the cold feed should be gravity fed from one of the tanks in the attic, and teed into the system (somewhere upstairs/near the valves or cylinder), before it goes back though the boiler to be heated?

I have contacted the plumber....just waiting for him to come by at some stage this week.

John.G

Yes, there is a smaller bore pipe coming out of the end of the small tank, this should be the cold feed, just follow it down and see where it tees in....probably into the cylinder coil return or close to that. The cold feed is not normally heated, it just makes up for any losses/leakages in the system.

CitizenFloor

I think I actually have a pic of that T junction already. I was taking pictures earlier, as I am anxious to figure it out.

Pic 1 Attic
Pipe 1 is the bore hole coming out of the small tank.
Pipe 2 is the vent pipe.

Pic 2 hot press
(Discounting the left most pipe which is not connected) -
- Pipe 1 is teed into the bottom of the cylinder.
- Pipe 2 (vent) is teed in at the middle.

John.G

If you are talking about the second last pipe T then that is not the return from the cylinder coil as the flow & return can be seen quite clearly now, you originally said tht the continuation of the cylinder flow pipe was the vent into the smaller tank so where is the second last main pipe going when it comes up through the attic floor??.

Apoligies, yes I think you are correct, the cold feed joins the cylinder coil return.

CitizenFloor

I mentioned the layout in a previous post, but probably didn't have good supporting pics. I numbered the pipes in the pictures, hopefully that clears up the layout

1 - Pipe coming out of the bottom of the small tank via a bore hole. I assume this is the cold water feed.
This pipe is T'd into the bottom of the cylinder.

2 - The vent pipe for the small tank - You can see it bend back over into the tank. This pipe is T's into the middle of the cylinder.
This T junction heats up when the water is turned on.

3 - A pipe that appears to be going into/coming out of the bottom of the large tank.

4 - Appears to be a vent for the large tank.

5 - Appears to be going into/coming out of the bottom of the large tank also.

John.G

Yes its pretty clear now thanks, as I edited above in my post, the cold feed is teed into the cylinder return., the cylinder flow/vent is as was so it does appear that the vent is blanked off with zone valve closed, it will be interesting to see what your tests show up.

Also when you are home you might post the details of the Tucson circulating pump and also details of the boiler.

CitizenFloor

The boiler is a GRANT Vortex Boiler House 50/90 - 26k

Ill check the pump details later.

CitizenFloor

Pic of pump attached.

Results of some testing:
I left the two auto bleed valves open.

I programmed my heating to only be on downstairs.
When I came home, I listened and there was no sound of air.
I turned off the valve for downstairs.

I turned on upstairs, left it on for a while while the boiler fired.
Listened and there was no sound of air.
I turned off the valve for upstairs.

I turned on the on the water zone, and the air started immediately, and there was continuous noise. Not a lot of air, but enough to build up over time.

I'm doing more testing.....letting everything cool down first.

But, assuming its only coming in when I turn the water on, does this point to it being a problem upstairs on the water circuit...the likely suspect being the zoned off vent? I have yet to test that with your bag of water method.

John.G

Very interesting....it seems that the vent being blanked off (as it is when HW zone valve off) is no problem for upstairs/downstairs but is a problem when HW only on. Why not try the HW only with the vent blanked off for this test as well, just stick something into the end of the vent pipe like a cork and see what happens and then do the same test or visa versa with a strong clear plastic bag of water taped to the end of the vent pipe.

I have read somewhere that no vent is required as long as the cold water feed pipe is 3/4 ins, I suppose the combined cold feed and vent behaves likewise..

Forgot to ask was/is there air venting from the ABVs on HW only.

CitizenFloor

Ah here.....before trying the cork, I turned on the hot water. No air noise now. No air noise on any of the zones now through the bleed valves. I have them all off now, and will check in a while.

It is always just air coming from the top ABV, never the bottom one.


Not sure what I can do now, besides wait to hear the air again, and cork the vent at that stage.

John.G

Very good, what speed setting are you on now?

CitizenFloor

John.G wrote: »

Very good, what speed setting are you on now?

I put it at PP2, it was going from around 7w to 21w depending on the number of zones that were open.....does that make sense? The more zones, the higher the number.

There was no pump over, but I could hear the pump, and the rad in the living room started clicking, so I changed it back to auto - 5w to 8w.
At this setting all the rads heat up at a normal rate. Its just that I have to bleed the one I mentioned previously.

At this rate, I am wondering if it was just some air left in the system....Thoughts on closing the bleed valves and running the system as normal, and see if air builds up over an couple of hours?

John.G

I feel that PP2 is the best overall, it ramps up with increasing zone opening but if you are happy with the Auto setting then fair enough but personally I think its far too low and will cause frequent boiler cycling. I would leave the auto air vents open for now, the only way that they will draw air in is if the part of the system they are venting is running at negative pressure and the water level inside them drops, very unlikely.

I have my own system on a PP setting of 4M (yours is 3.2M) and the power demand varies ~ 14W/21W and has worked very well for the past year.

CitizenFloor

John.G wrote: »

I feel that PP2 is the best overall, it ramps up with increasing zone opening but if you are happy with the Auto setting then fair enough but personally I think its far too low and will cause frequent boiler cycling. I would leave the auto air vents open for now, the only way that they will draw air in is if the part of the system they are venting is running at negative pressure and the water level inside them drops, very unlikely.

I have my own system on a PP setting of 4M (yours is 3.2M) and the power demand varies ~ 14W/21W and has worked very well for the past year.

I switched back when it started clicking. Does that not mean the pressure is too high or something?......Ill try PP2 again.

John.G

No, that PP setting of 3.2 is very modest, any clicking/noise I would think is still caused by air bubbles, personally, I would just blank off that air vent but firstly I would just hold even a cup full of water up under it and see what's happening, it will only take a minute.

CitizenFloor

John.G wrote: »

No, that PP setting of 3.2 is very modest, any clicking/noise I would think is still caused by air bubbles, personally, I would just blank off that air vent but firstly I would just hold even a cup full of water up under it and see what's happening, it will only take a minute.

Okay, we're back on PP2, no valves open and sitting at 7w. The house is roasting, and I have been running up and down the stairs, and into the attic



I have everything off for a little while. Ill turn it back on shortly and get up to the vent with two glasses of water. 1 for me, and 1 for the vent

John.G

Cheers! but why is the pump showing 7W with no (zone?) valves open, it should have stopped or is it on overrun.

CitizenFloor

John.G wrote: »

Cheers! but why is the pump showing 7W with no (zone?) valves open, it should have stopped or is it on overrun.

I am not sure what over run is.....Auto always sat at 5w. PP2 sits at 7w. All zone valves are off......Is that unusual?

No pump overflow....

John.G

Some boilers require the circ pump to run on for a few minutes after all the zones are satisfied, if no overrun required then the pump should stop immediately that the last zone valve closes. If you let the system off for hours are you saying that the pump still keeps running?, if so, this is not correct and could point to a zone valve microswitch problem but this would also keep a run signal to the boiler and you should hear it start up briefly a few times during the night on its own boiler stat but certainly not normal.

CitizenFloor

John.G wrote: »

Some boilers require the circ pump to run on for a few minutes after all the zones are satisfied, if no overrun required then the pump should stop immediately that the last zone valve closes. If you let the system off for hours are you saying that the pump still keeps running?, if so, this is not correct and could point to a zone valve microswitch problem but this would also keep a run signal to the boiler and you should hear it start up briefly a few times during the night on its own boiler stat but certainly not normal.

Not sure about hours....the system has always been ticking over when I am here. But the heating has generally been on, or on recently. Ill leave it off for an hour, and check.

Starting to think I need to get a second plumber to look at the whole thing.

CitizenFloor

Just noticed this coming out of the side of the boiler, and into the waste from the washing machine. Is that possible the vent for the boiler?

John.G

OK, if you are absolutely sure that the pump is still running then that means its running against
a closed head which will result in pump cavitation and cause air bubbles to form and will shorten the life of your pump, PP2 isn't too bad as the pump will ramp down to maintain a head of ~ 1.6M but if it was on fixed speed 2 or 3 then it will be pumping against a head of 3M or more and spells even bigger problems.

John.G

CitizenFloor wrote: »

Just noticed this coming out of the side of the boiler, and into the waste from the washing machine. Is that possible the vent for the boiler?

No, that's the condensate trap drain I would think and its called that because you have a condensing boiler.

CitizenFloor

John.G wrote: »

OK, if you are absolutely sure that the pump is still running then that means its running against
a closed head which will result in pump cavitation and cause air bubbles to form and will shorten the life of your pump, PP2 isn't too bad as the pump will ramp down to maintain a head of ~ 1.6M but if it was on fixed speed 2 or 3 then it will be pumping against a head of 3M or more and spells even bigger problems.

The pump is still going at 7w....

The boiler never starts during the night....What is overrun, and how do I determine if its required?

John.G

Can you kill the power completely to your system there should be a circuit breaker somewhere.

Also just check your boiler house and see if there is a wall thermostat which just may have been connected to your pump, if there is (its called a frost stat) check its setting and turn it down to say 4C and see if the pump stops.

CitizenFloor

John.G wrote: »

Can you kill the power completely to your system there should be a circuit breaker somewhere.

Also just check your boiler house and see if there is a wall thermostat which just may have been connected to your pump, if there is (its called a frost stat) check its setting and turn it down to say 4C and see if the pump stops.

I have a switch that will turn on the off the pump altogether, and a switch for the boiler. Should I just switch off the pump completely? Or both?

I have a smart system installed (Ember, it has an inbuilt frost setting set at 5 degree, if the temp in the house drops below that temp, it kicks in). I turned it off to rule that out.

No stats in the shed that I can see, apart from the main one set at 65/70....pictured.

John.G

I'd suggest switching both off until morning, must go out for awhile.

CitizenFloor

John.G wrote: »

I'd suggest switching both off until morning, must go out for awhile.

Okay, I can do that.....what are we trying to achieve? Let the boiler cool down completely to see if the pump stops?



The flow pipe coming out of the boiler now, is still really hot....the pipe with the pump (the return) is luke warm.

John.G

Really its to stop the pump running when not needed but it will be interesting to see when you do switch the power back in and before any zone valve call....if both the pump & the boiler fire up. I'll post a basic logic diagram in a minute once I find it.

Here it is, the main thing to remember is that even if the boiler is being called as well as the circ pump is that the boiler will still just cut in/out on its own (boiler) stat which would normally have a hysteresis of say 10C so maybe cut in at 60C, cut out 70C (setpoint) it could, at the very worst, trip the hi level stat if the residual heat in the boiler (due to no circulation) causes the temperature to reach ~~ 113C I think but while certainly not desirable can be tolerated for a few days/week or so as long as you take the precaution of switching off both supplies at night. Also remember your plumber maybe did not do the wiring so keep him in the picture.

https://www.plumberparts.co.uk/advice/heating-systems/s-plan-heating-system

I see that you said in another post that the boiler doesn't cut in at night so even less worries.

CitizenFloor

I had to turn it back on this morning, when I did, all zones were off, but the pump still spun up to 7- 8w. The boiler did not fire until I opened the a zone valve.

I am assuming that this is either:
1 – A bad zone valve that is getting stuck etc.
2 – Incorrectly wired zone valve/pump/boiler etc.

I think the latter is more likely, as the valves seem to be working perfectly.
I.e. I turn a zone on/off with my phone, the valve pin moves, the light comes/goes off on and the heat starts/stops in that zone.

I have a theory that I will test later. And please, tell me if I am completely off the mark.

In PP2. The fact that the pump is a constant 7 – 8w, suggests to me that 1 zone may be calling for heat all the time.
I base this on the fact that when I turn on all zones, it’s at 21w. And I am pretty sure I saw it at 14w too.
So I think that each zone corresponds to ~7w.
I plan on testing different combinations of zones later, to see if I can identify a potentially incorrectly wired zone. Luckily I have on-going electrical work, so I can ask the electrician that wired it to take another look (I assume it’s the electrician that needs to look at it and not my plumber, who won’t be back till next week).

Now that you have mentioned the fact that air could build up with a constantly running pump, I think I have been hearing a gurgling at the junction where all the valves are located, when the heating comes on initially. So the pump runs constantly creating an air pocket at the highest point (i.e. the valve junction, when no zone is on), and then when any valve opens, the air goes in to whichever zone is open.

Could this be the cause of the air problem?

The pump is off again now.

John.G

It looks almost certain to me that the pump is wired incorrectly but not the boiler because you said the pump started up as soon as power was restored but the boiler didn't.... until the zone valve opened.
Regarding 7W & 1 zone, I don't have pump power/curves but to test your theory just shut the discharge valve on the pump (the one nearest the boiler) for a minute or two with pump running under any condition and note the power, then reopen the pump discharge valve. I'll get back later re power/zone.

Yes, the constantly running pump against a closed head can/will cause air build up.