Air keeps getting in hydronic heating system

B2mett

Hi. I recently moved into a house that had a new boiler installed. The house has two zones. One on the main level and one in the basement. Each has a circulating pump. No zone valves. There is a blatterless compression tank on the supply side. There are Bell & gossett airtrol tank fitting ( atf-12) on both supply lines. There is no auto fill or vent or air separators. When I moved in there was a lot of air in the system. After I purged it I had heat throughout. After about 3 days the gurgling started. I purged again and it was good for another 3-5 days. This has been the case sines October. I keep it at 18 psi. The pressure stays consistent so I ruled out leaks. I drained the compression tank. The pressure at the tank is the same as the system. 18psi. I have the pumps on the lowest speed but have tried all three with the same results. I’m running out of ideas. Any help would be greatly appreciated!!
thanks

hot_rod

Cast radiators? Fin tube? Radiant? What type of heaters?

B2mett

Tube and fin. 

hot_rod

Either all the air is not getting purged out at fill, or air is getting in somehow. Blast it with a power purge from a garden hose, lots of flow to push air out. Stay below 30 psi.

Move beyond the horse and buggy air elimination/ expansion:)
Consider a microbubble air purger and diaphragm expansion tank.

leonz

B2mett said:

Hi. I recently moved into a house that had a new boiler installed. The house has two zones. One on the main level and one in the basement. Each has a circulating pump. No zone valves. There is a bladderless compression tank on the supply side.

There are Bell & Gossett Airtrol tank fitting (atf-12) on both supply lines.

There is no auto fill or vent or air separators. When I moved in there was a lot of air in the system.

After I purged it I had heat throughout. After about 3 days the gurgling started. I purged again and it was good for another 3-5 days.

This has been the case since October. I keep it at 18 psi. The pressure stays consistent so I ruled out leaks. I drained the compression tank. The pressure at the tank is the same as the system 18PSIG.

I have the pumps on the lowest speed but have tried all three with the same results. I’m running out of ideas. Any help would be greatly appreciated!!
thanks

================================================================

Let us back up here a little and start at the beginning shall we?

I am very glad to hear there are no auto fill valves or automatic
air vents in this heating system.

I have a 15 gallon Bell and Gossett Steel Compression Tank with a
sight glass tube water level gauge and a single ATF-12 airtrol valve
under the tank and I heat my home very well with it using a
Bell & Gossett NTF-25 circulator on speed 1.

There should only be one ATF-12 for one steel compression tank
in your system NOT TWO.

The next question is this, is there one ATF-12 mounted under the
steel compression tank in use?

We can fix this, all we need are many pictures of your system to see
what the plumber did to install the heating system.

You do not have to tear anything out and replace it with anything else
to get this right.

Whoever installed the new heating system did not know how to install it
correctly by using an internal air separator or air scoop that should be
connected to the ATF-12 Airtrol fitting under the Steel Compression Tank.


We can help you with this plumbing mistake made by the boiler installer.

B2mett

I miss spoke. There is an ATF-12 airtrol fitting under the compression tank. Both zone supply lines have a B&G flow control valve on them. I will post pictures when I get home 
thanks!!

leonz

Hello B2mett,

Thanks for that, you had me worried there for a few minutes.

B2mett

here are some photos of the set up. 

B2mett

leonz

Thanks for posting the photos, I would start by opening up the 2 B+G flow checks leaving them open and raising the thermostat all the way up and waiting for a while before I started bleeding the radiators again.
Heating the water to a higher temperature will help move the water and air bubbles through to the steel compression tank.

I am glad to see the very large compression tank hung in the ceiling joists of your basement.

If you can afford to do it your boiler needs to be plumbed correctly to avoid this problem in the future and always have good heat in the house. I do not see a low water cut off or where the triple aquastat is located.

I would like you to purchase three of Dans well written hydronic heating from his bookstore.

These books are "CLASSIC HYDRONICS"; "HOW COME" and "PUMPING AWAY".

I have all three of them plus "WHAT HYDRONICS TAUGHT DAN HOLOHAN" and they are a valuable resource for plumbing and heating.

Dan makes his writing fun and easy to understand for both the plumber and lay person alike and he provides the reader with his life time of plumbing and heating experience plus the many lifetimes of experience from the DEAD MEN that created the heating and plumbing we use today and the many scientists that created the theories of fluid dynamics, gas law, Fahrenheit and Celius temperature and water chemistry that are in use today.

Dan talks about the Dead Men in his writing with reverence explaining how they came to the conclusions they did which they then applied to hydronic heating/radiant heating in designing steam heating, gravity hot water heating systems and pumped hot water heating.

You can purchase these books from the Heating Help Bookstore with a credit card and Dan ships the books to you avoiding a middleman and all profits go to the author.

Once you start reading his books you will see how your boiler can be plumbed in a much better way to eliminate air bubbles.


Leon

B2mett

Thank you!

kcopp

That compression tank is really supposed to be connected into the boilers "built in air scoop"... some oil boiler still have this.. eg. Peerless wbv and the weil McLain wgo.
Your boiler does not have that type of a set up.
When they piped in the new boiler it looks like they just put a tee into the piping to one of the zones and hoped for the best.
The water moves too fast for the air to get to the compression tank.
You could try the tapping where the pressure relief valve comes out of the boil and add a tee there.
Ideally, I think the best option is to go to an air Seperator and a diaphragm tank.

EricPeterson

kcopp said:

That compression tank is really supposed to be connected into the boilers "built in air scoop"... some oil boiler still have this.. eg. Peerless wbv and the weil McLain wgo.
Your boiler does not have that type of a set up.
When they piped in the new boiler it looks like they just put a tee into the piping to one of the zones and hoped for the best.
The water moves too fast for the air to get to the compression tank.
You could try the tapping where the pressure relief valve comes out of the boil and add a tee there.
Ideally, I think the best option is to go to an air Seperator and a diaphragm tank.

From SupplyHouse:
Airtrol Tank Fittings must be used with the appropriately sized In-Line Airtrol or Rolairtrol air separator.

Eric Peterson

Robert_25

The way your system is piped currently the air will not migrate into the expansion tank as intended. I agree with the suggestion above that adding a tee at the relief valve tapping would probably have the best chance of success, short of a more extensive re-pipe.

leonz

Whoever plumbed that boiler together did not know what they were doing and made it much worse by not piping it better and correctly as it apparently has no top tapping's judging by the photo images he was so kind in providing to us.

Whoever did this did not even place the boiler on half blocks to keep it off the floor and that is not good at all.

B2mett does not have to waste money installing a diaphragm tank that will require more pipe and ripping out the existing tank that is intact as he already has a steel compression tank of the proper size and an Airtrol valve hanging in the ceiling joist above the boiler.

He needs to have a plumber pipe it correctly and install an internal air separator that is the correct size for his boiler tapping's and add the correct length of pipe and elbows to create the correct flow for it to work and create the proper path and angle for the air bubbles to rise to the airtrol valve and into the steel compression tank.

Bmett will have to decide if this repair job is going to have to be done now or in the summer to have it done correctly as the correctly sized Internal Air Separator has to be plumbed horizontally above the boiler and the circulators should be pumping away from the boiler after the Internal Air Separator.

The way circulators are plumbed the entire system would have to be drained to change one or both of them as there are not isolation valves with gauge ports installed in the system.

He is going to continue to have problems with air bubbles until it is corrected.

To Bmett;

I guess for now you could shut the gas off on the boiler and shut the connection to the steel compression tank off and open the fill valve and leave the vent on the last radiator on the third floor open and continue to drain water and air from the system while the water in the system is circulating on speed one and you may be able to purge the excess air in the system after a few hours of circulation.

Speaking as a homeowner I am genuinely sorry that you are going through this and it's a shame that it was not done correctly.

B2mett

Thanks for all the help.