Air in Heating System

[penguinventures]

I can hear air bubbles in the pipework going to from the boiler. How do I rectify this? Air bubbles can also be heard travelling through the pump.

The system is GF. A new pump was recently fitted (last 2 weeks). The system's been gravity flushed from drain points around the house till water runs clear. As yet I have not stuck inhibitor in.

There is an air trap (bottle shaped copper) apove the pump which I assume is working.

Any guidance please much appreciated...

 

[LUNAT]

HI

Try bleeding the radiators.
if any work was done recently air should clear in few days.
if the pump is set on low,try to set it on max for few days.

 

[penguinventures]

Hi

Thanks for the advice. I bled the system last night and removed air from two radiators.

I can still hear what sounds like bubbles in the pipes to and from the radiator. As you advise I'll put the pump on its highest setting and bleed again in a couple of days.

Ta

 

[penguinventures]

Hi Lunat,

Still lots of noise tonight.

The noise in the pipes going to and from the boiler sound likes rushing water just like there's lots of air in the pipes. Its noticeably worse once the house stat reaches temperature and water is only flowing through the hot water tank coil. Its ok when the system first starts and the water is only cold to warm - once it gets hot then that's when the noise starts.

The pumps running at full speed now. Normally its on the middle speed setting. Running it on low last night the boiler shut down I assume having overheated. So the middle speed seems to be the correct setting.

I'll bleed the radiators again in the morning.

Any other suggestions on the possible cause and cure? Anything else I can do besides doing what I'm doing?

Thanks

 

[nairb999]

You have hit on the same problem as me.

You may wish to read my post " Converting close coupled to combined feed feed & vent " plus a number of other posts I have made.

I am an average DIY er so use as reference only but there is some good advice from experienced people on all posts - you may wish to follow their guidance.

Using the lowest speed setting for me makes the bubbling less noisy but still there.

 

[penguinventures]

You may wish to read my post " Converting close coupled to combined feed feed & vent " plus a number of other posts I have made.

Thanks for the reply - you seem to be having far more trouble than I - you have my sympathy! Hopefully the design of my system can remain unchanged.
Having bled the radiators today, removed only a little bit of air, then read your post - I am starting to think that maybe there is debris trapped in the pipework going to and from the boiler.

It may be trapped as the boiler is downstairs and the pump/distribution to radiators is all upstairs - any heavy stuff the flow of water cannot lift upstairs just rattles about in the pipes adjacent to the boiler? (or am I thinking rubbish?)
I did not flush this part of the system as part of the pump change and maybe now I should? However the washer is trapped in the boiler drain off point (welded in I should think) so I can't flush it through until I get that sorted.
Maybe you can tell cos its obvious I too am a diy'er who gratefully appreciates the advice of people who know!

 

[penguinventures]

I've left the boiler drain point as it is as I don't want to break it.
I did however find the boiler air bleed and released some air.

The circumstances of noise in the boiler pipes is now as follows
Noise occurs only when the boiler has reached and is maintaining temperature.
Noise is there when the electric valve for the tank is open only
Noise is there when both tank and rad electric valves are closed
Noise is not there or greatly reduced when the valve for the rads is open only
Noise is reduced when the valves for both rads and water are open
Fizzy water can be heard going through the pump in all circumstances apart from when the water is cold. With the system not running I have been bleeding the pump as per MI.

I have reduced the pump speed to setting two of three in case of cavitation. If the pump's on setting one then circulation does not get to all radiatiors and I when I did try it earliar in the week I think it caused the boiler to overheat.

Anybody > please help!

 

[LUNAT]

HI

1.check the flow and return pipes close to the boiler .
are they really hot ? if yes then boiler stat bcould be faulty
causing water to overheat.
2.if possible drain the water and fit an AIR VENT close to where
air bubble noise can be heard.
3.check if all the valves are open (especially when the boiler is ON)
and not partially closed thus obstructing the full flow.


keep informing us

 

[penguinventures]

1.check the flow and return pipes close to the boiler .
are they really hot ? if yes then boiler stat bcould be faulty
causing water to overheat.
2.if possible drain the water and fit an AIR VENT close to where
air bubble noise can be heard.
3.check if all the valves are open (especially when the boiler is ON)
and not partially closed thus obstructing the full flow.

Hi Lunat - thank you for the reply...
1. The flow & return pipes are not excessively hot. I think the boiler stat is doing what it should and the boiler is not overdoing things - tomorrow I'll go through the boiler diagnostic checks just to be sure.
2. I see your thinking on fitting an air vent close to the boiler however I am hesitant at going down this route as the system design is 10 years old plus and up until this last year its started to play-up. The air vent may be the treatment but not necessarily the cure of the root cause.
3. There are two electric valves adjacent to the pump and hot water cylinder - they seem to both open and close fully as they should. All other valves in system (rads) are wide open due to the recent flushing exercise. I will close them down balancing the system once I've resolved the current air issue. Unless of course the unballanced system is the cause? There is one new TRV fitted on a rad which does whatever it wants - not sure if this has any effect?

The new pump is a 15-60 Grundfos which replaced the same. The old one was really noisy and vibrated due as it turned out to its rotor being full of solidified sludge/muck. Maybe the pump in its as new state is too powerful for the system when both electric valves are closed and the bypass is in use or when only short immersion circuit is in use? As I mentioned, the pump running on setting 1 doesn't circulate to all rads, but tomorrow I'll see what difference it makes when heating the tank only.

BTW - I have checked the vent and feed to the loft tank and both are fine. I cleaned the tank of all sludge as part of the pump change.

Time to go the pub I think!
Cheers!

 

[penguinventures]

Heating's been off for a while and all was cold so so I clicked the room stat. The boiler stat was set at 3 (with the old pump used to be in on 4) wound it down to 2.5. Held fingers on flow and return - just as flow was starting to hurt my finger the boiler cut-out. So, I think the boiler temp controls are ok. So far there are NO air noises in the pipes & pump. I'll give it a while and see how well the system operates on 2.5. It'll be interesting to see how well it heats a cold house and tank in the morning.
I'll check the boiler output tomorrow with a thermocouple - manual states 80 to 84 degC water flow shut down.
Would be nice if all works well on 2.5 and this is the cure

 

[LUNAT]

HI

15/60 grundfos ?
i would prefer 15/50 for most systems.

 

[penguinventures]

Hi Lunat

Lost my thermocouple so no temperature measurements possible - yet.

Had to turn the boiler up tonight as the heat output from the radiators was insufficient to heat up the house up. Its set on 3 so not as high as it used to be.

I stuck with the 15/60 as I assumed as 7/8's of the system is poxy microbore the system probably needed the higher spec pump.