Open system sucking in air, closed system still sucking in air! Any help or pointers?

[kugaman1]

Hi All.
I know this is a popular discussion topic....Ive reads lots of threads on it but can't find the answer to my issues.

We live in a 3 bedroom bungalow.

I had an old Potterton gas boiler open vented system. This was located in the loft along with the pump and head tank.

There are 7 radiators on the system. The hot water and heating are on their own zone valves, the only connection between them being a manual bypass valve.
Over the years, we've continually suffered with air ingress to the radiators.

Replaced the boiler with a new Worcester Bosch condensing unit, much more efficient but still giving air ingress in radiators. Replaced the pump with a new grundfoss one. No signs of air at the pump, runs super quiet at mid speed.

I have to bleed one of the radiators every couple of days and get a lot of air out of it. Others need bleeding less often.

After having 3 different plumbers look at it, we made the decision to pressurise the system.

So the head tank for the boiler is gone and the system is now pressurised to 1.4 bar.

There are no signs of water loss at all. However, Im still getting a lot of air in the system.

Like I say - one of the radiators (I think its no 4 in the line) seems to be the main hotspot for air, always needs bleeding almost daily.

I have checked the air from this radiator using a gas meter from my work, its definitely not hydrogen.

So, Im looking for ideas as to how on earth my system is pulling in so much air and where from? Im at a total loss, weekly bleeding of the system is my life nowadays. None of my local plumbers knows what's going on and as mentioned, pressurising the system made no difference at all!

As I say, there's no sign of water loss, the system holds pressure and doesn't need topping up.

Some photos attached if it helps? I can always take other pics if required.

Thank you in advance for any advice you might offer.

cheers

Andy

 

[Johntheo5]

Hi Andy,
I see the EV water end is on top, have you tried cracking open the drain to check for air, the EV may not have been filled properly on installation although one would think all the air would have been removed by now with all that venting. Do you have to top up each time you vent the rads? Also check that the pump inlet and outlet connections are tightened adequately. Check that the EV is teed in before the pump inlet.
What model Grundfos and what is its mode and setting?, ensure its pumping in the right direction.

 

[fixitflav]

I have checked the air from this radiator using a gas meter from my work, its definitely not hydrogen.

Have you tried lighting it? That's my test for hydrogen, and I can't think of anything else it could be.
Is there inhibitor in the system?

 

[Mottie]

I could never get all the air out of my system both when open vented and sealed. I added one of these and not a single bubble has ever appeared. Has to be fitted as near as possible to the boiler outlet.

 

[kugaman1]

Hi John, thank you for taking the time to reply.

Yeah, have checked the EV several times, always water, never air from it.

Yes, every time I vent all of the air from the radiators, I basically lose all pressure in the system, as I vent off so much air and water. I use a 500ml jug when venting and normally fill it with water while venting the worst radiator. I know Im venting the air off, but in the process there is also a lot of water coming out under pressure.

I will check where the EV is tied in tomorrow, although as mentioned, this has been a problem since before the EV fitting, hence why it was fitted.

Im not sure about the pump model and direction, again I will have a look tomorrow - I did check the connections months ago when trying to find how the air gets in and the pump connections are solid.

In essence, we've gone from an open vented with an old boiler and pump to an open vented with a new boiler and pump and now a closed system….yet the problem persists!

 

[kugaman1]

I could never get all the air out of my system both when open vented and sealed. I added one of these and not a single bubble has ever appeared. Has to be fitted as near as possible to the boiler outlet.

Thanks Mottie….

Im sure that would help, but my focus at the moment is to try and figure out why and how the air is getting in…there just seems to be so much every few days that I feel theres a fundamental issue somewhere!

 

[ericmark]

If the diaphragm has failed you will never win. As to how to test, sorry, not a clue.

 

[kugaman1]

If the diaphragm has failed View attachment 350375 you will never win. As to how to test, sorry, not a clue.

It was only fitted around 6 months ago - my problems exist before and after fitting. The system holds pressure - the only time pressure is lost is when I vent the system - I then have to refill it.

 

[kugaman1]

Have you tried lighting it? That's my test for hydrogen, and I can't think of anything else it could be.
Is there inhibitor in the system?

Yup, borrowed a Hydrogen specific meter from work and got nothing….vented this afternoon and tried lighting it…again nothing. Im just at a total loss……

 

[Mottie]

Thanks Mottie….

Im sure that would help, but my focus at the moment is to try and figure out why and how the air is getting in…there just seems to be so much every few days that I feel theres a fundamental issue somewhere!

I’m not a plumber or heating engineer but if it’s a pressurised system, the system must be producing it internally somehow as surely air at atmospheric pressure would not make its way into a sealed and pressurised system, would it?

 

[Johntheo5]

Hi John, thank you for taking the time to reply.

Yeah, have checked the EV several times, always water, never air from it.

Yes, every time I vent all of the air from the radiators, I basically lose all pressure in the system, as I vent off so much air and water. I use a 500ml jug when venting and normally fill it with water while venting the worst radiator. I know Im venting the air off, but in the process there is also a lot of water coming out under pressure.

I will check where the EV is tied in tomorrow, although as mentioned, this has been a problem since before the EV fitting, hence why it was fitted.


Im not sure about the pump model and direction, again I will have a look tomorrow - I did check the connections months ago when trying to find how the air gets in and the pump connections are solid.

In essence, we've gone from an open vented with an old boiler and pump to an open vented with a new boiler and pump and now a closed system….yet the problem persists!

Venting with pump off?.

Have you got barrier plastic piping in the system?

Is the pump on the boiler flow?.

Also tighten up the pump isol. valve gland nuts.

That Spiro Tech deaerator might be well worth fitting as it will just vent air/gasses, you are introducing air in the raw water with all that excessive topping up as you are bleeding off water as well as venting air each time.

 

[kugaman1]

Venting with pump off?.

Have you got barrier plastic piping in the system?

Is the pump on the boiler flow?.

Also tighten up the pump isol. valve gland nuts.

That Spiro Tech deaerator might be well worth fitting as it will just vent air/gasses, you are introducing air in the raw water with all that excessive topping up as you are bleeding off water as well as venting air each time.

Hi, yes define only ever venting with the whole system off.
Not sure how to tell if the pump is on the boiler flow?
No, there’s no plastic piping- the entire system is copper pipe work.
I will check the glands on the pump tomorrow but the pump runs totally silent, never heard any trace of air from it.

Two questions-
Would an auto vent on the radiator where the air tends to gather be a good idea?
And….could the manual bypass between the hot water and heating systems be an air entry point? I mean, the hot water system isn’t pressurised but the heating is….could air get in between the two somehow?

 

[Johntheo5]

Hi, yes define only ever venting with the whole system off.
Not sure how to tell if the pump is on the boiler flow?
No, there’s no plastic piping- the entire system is copper pipe work.
I will check the glands on the pump tomorrow but the pump runs totally silent, never heard any trace of air from it.

Two questions-
Would an auto vent on the radiator where the air tends to gather be a good idea?

And….could the manual bypass between the hot water and heating systems be an air entry point? I mean, the hot water system isn’t pressurised but the heating is….could air get in between the two somehow?

Follow the pump inlet back to the boiler your manual wll then show which is the boiler flow/return.
Edit: Its on the flow because I can see a magnetic (isolating valves) filter on the other pipe under the boiler, the flow pipe should be the hottest pipe, check for a arrow on the pump body pointing from right to left and check that the EV outlet is teed into the pump inlet, ie, somewhere on the right hand of the pump.

Could try one of those Aladdin? type rad vents, don't know how effective they are.

What is the manual bypass for between the HW and heating systems?.
Edit: I see thats the HW primary and CH primary so probably cracked open to give some circulation during pump overrun when the zone valves close and the boiler shuts down.

More food for thought.

* Resolved * Air in the central heating system

Feel compelled to post this as this issue has been the bane of my life for last month. Finally this evening discovered the problem. Searching various forums it appears many people have similar issues, this is how resolved mine / something easily ruled out. Problem - Closed loop system...

www.diynot.com

 

[fixitflav]

Yup, borrowed a Hydrogen specific meter from work and got nothing….vented this afternoon and tried lighting it…again nothing. Im just at a total loss……

Can you do a rough sketch of the layout, with levels? Maybe there is negative pressure at some point, sucking air in.

 

[kugaman1]

Follow the pump inlet back to the boiler your manual wll then show which is the boiler flow/return.
Edit: Its on the flow because I can see a magnetic (isolating valves) filter on the other pipe under the boiler, the flow pipe should be the hottest pipe, check for a arrow on the pump body pointing from right to left and check that the EV outlet is teed into the pump inlet, ie, somewhere on the right hand of the pump.

Could try one of those Aladdin? type rad vents, don't know how effective they are.

What is the manual bypass for between the HW and heating systems?.
Edit: I see thats the HW primary and CH primary so probably cracked open to give some circulation during pump overrun when the zone valves close and the boiler shuts down.

More food for thought.

* Resolved * Air in the central heating system

Feel compelled to post this as this issue has been the bane of my life for last month. Finally this evening discovered the problem. Searching various forums it appears many people have similar issues, this is how resolved mine / something easily ruled out. Problem - Closed loop system...

www.diynot.com

John,
Thanks again thats really helpful.
I will check the pump and EV later.
I did see that other post about air ingress but disregarded it as I have a magnaclean. However, I will check it - It did come with spare O Rings….maybe time to replace them just in case…