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Boiler with compression tank, want to add B&G Airtrol fitting.
OldBoiler65
Member Posts: 29
Hello again. I posted on here a month ago and received some great advice with another problem. I have an American Standard G210 gas boiler with a ceiling mounted compression tank. I think I'm losing the air charge in it. I end up with air in the upstairs radiators all season long. The boiler pressure climbs also as the season goes. Last season I drained the tank and refilled part way through the winter and that solved the problem for a while. I'm pretty sure I don't have any leaks in the tank. Just bought a Bell & Gossett Airtrol valve model ATF-12 after reading about them online. The piping from my boiler to the tank might need reconfigured. Thats all original to the installation in 1965. Do you think this will correct the problem and any tips for plumbing it in? I have a couple
pictures of the setup and I can get more or provide more information. Thanks!
pictures of the setup and I can get more or provide more information. Thanks!
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Comments
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Where’s the circulator located? Please post a pic.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.1 -
Good morning oldboiler65,
IS the boiler feed water valve open or closed????????????????????????
Would you be so kind as to provide us with more pictures of the opposite end of the steel compression tank if you would be so kind to do so as that will help us a great deal.
The ATF-12 should be connected to the piping that is connected to the circulators pressure flow to the radiators with a gradual riser pipe connection.
Ideally the opposite end of the tank is where the ATF-12 valve could or should be located to allow the gradually slope of pipe to allow the trapped air bubbles in the heating system to rise gradually to the steel compression tank and dissolve into the air blanket and then allow the cooler water to drop back into the hot water circulating into the heating system.
Unless the boiler has an air baffle casting in the steam chest to slow the flow of air bubbles where the relief valve is located you have no point of pressure change.
I hate to bring this up, but the steel compression tank was not plumbed correctly. The riser to the steel compression tank should not be plumbed as it is now it requires a gradual slope to the compression tank
from the pressure side of the circulator.
The ATF-12 allows a ratio of one third air to two thirds water to allow the air blanket above the water charge to compress and create the point of pressure change to allow the circulator or circulators to move water to the radiators and back to the boiler sump.
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IF THERE IS AN AIR BAFFLE CASTING IN THE STEAM CHEST WHERE THE RELIEF VALVE IS LOCATED:
The boiler should be shut off for a short period to allow the piping to be corrected.
PLEASE NOTE- The water supply MUST must be shut off after the boiler AND heating system is filled NOT LEFT OPEN.
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The blue handled globe valve in the copper pipe leading to the steel compression tank needs to shut off.
2. the steel compression tank needs to be drained to empty it completely.
2a. the ATF-12 is then installed with either teflon tape or pipe dope and tightened to the correct position to allow the N.P.T. tapping is in line with the riser pipe.
2b. the riser pipe is then reconnected to the female N.P.T. tapping in the ATF-12 Airtrol valve.
Once this is done the small globe valve can be opened to refill the steel compression tank with boiler water.
Begin filling the steel compression tank and while it is filling open the air vent at the base of the ATF-12 Airtrol Valve and you will hear air whistling out of the tank as the water is filling the steel compression tank.
Once you have water spitting out of the drain valve please close it hand tight and leave it the system is now balanced and you can bleed the remaining air out of the radiators if any is left after a few hours of run time.
You may be able to use a run of rigid pex from the vertical riser to the ATF-12 AIRTROL valve but I am not sure if it can tolerate the temperature.
IDEALLY your system really needs work and should be repaired to provide trouble free service by plumbing it correctly by correctly the plumbing for the steel compression tank
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It's located on the return. At the lower right of this pic.Ironman said:Where’s the circulator located? Please post a pic.
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Leonz: The feed water valve is open. It is a Taco 3450 and there is a valve to shut it off inline. Thats something I didn't know for sure, to shut it off after filling.
Yes, I can get more pictures as soon I get back where the boiler is as I'm not currently there. I can tell you the opposite end is where the drain valve is. So, I would want to put the ATF-12 on the far end of the tank from the boiler I take it. The manual for the boiler mentions something that may be the air baffle in the relief valve area.
I figured that the tank wasn't plumbed in right. The pipe just goes straight up, no slope and right to the tank end you see at the boiler.
Thanks for your help! It sounds like I should be able to get it working better with a little work. If you or anyone needs any further information or pictures, I'll be glad to get them as soon as I can. I might be there later this evening.
Thanks for the book suggestion I'll check it out.0 -
Yes please provide us with more images if possible as it will
only help us to help you.
The feed water valve must always be shut off!!!!!!!!!!!!!!!!!!!!!!!!!
That is unless you are refilling the system after a massive
system failure like a broken radiator/ cracked circulator or
blown circulator gasket or clearing a waterlogged compression tank.
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IIRC, the instructions state to use 3/4" pipe for the horizontal length of pipe to the tank. With some slope on it so the air will migrate up into the tank.1
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@OldBoiler65, What you have is a typical heating system that was installed when coal was king. I would say that most if not all of your radiators are cast iron sectional type, if there are any that are not that type, they were installed some time after the original installation. The hand fired boiler did not have a circulator pump. Thermosyphon or gravity was the way the water flow happened. That is why the original pipes are so big. At some point, in the 1960's perhaps, the boiler was replaced with what you now have. Since the replacement boiler was equipped with a circulation pump, the contractor could use smaller pipes and to save money the left side and the right side piping was joined together with a tee fitting, in order to use the ONE pump that came with the boiler.
One of the things that the plumbers, pipe fitters and burner men of the 1960s did not take into consideration was something called Boyle's law relating to the physics of how liquids contain air in solution. (think Carbon Dioxide inside a soda water bottle). And when you change the pressure and the temperature of the water, you change the amount of air that the water can hold in solution. AND GUESS WHAT? Your heater and your circulator pump changes the temperature and the pressure of the water on every heating cycle over and over again and again. Because of this phenomenon, the air in the tank can get absorbed into the water in the tank. If that water (loaded with extra air in solution) finds its way into the radiator system. The boiler will heat it up and the circulator will pump it around the pipes and radiators where the air gets released. Of course if that air is released in the radiators, that radiator will be colder than the ones that have no air in them. And someone will let that air out of that radiator. Once you do that, what will replace that air that leaves the radiator? Water will fill the system to bring the pressure back up to the auto-fill pressure. So air leaves the tank and finds its way to the radiator where someone lets the air out, which is then replaced by water. Do this enough times and you will have a waterlogged expansion tank.
By adding the AirTrol® fitting correctly, all the air in the system will accumulate in the high spot in the boiler (Where your relief valve is) and the fitting in the tank will prevent the air migration out of the tank into the radiators. If done correctly, you will actually have a system that will purge air from radiators and release it to the tank. (not the other way around as is happening now).
Go one better and place the circulator pump on the supply side of the boiler, and you will increase the way that Boyle's Law moves air from the radiators into the tank. Use the science to your advantage.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Alright I'm back with more pictures. I also looked closer at the boiler manual and followed it and the suggestions I received here. What I did for now was drain the tank again and refilled to roughly 12 lbs. Then shut off the water feed after. I let the boiler run a while and this time I could actually hear what I sounded like air bubbles traveling up the pipe and into the tank. Never heard that before till now.
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EdTheHeaterMan: Yes, I have all cast iron radiators probably 1920's vintage. Thats great information. I've heard a little about how these gas boilers were installed into a gravity system where a coal boiler once was. This is all pretty new to me since I've owned the house and system about two years. I thoroughly enjoy reading and gathering more knowledge on how it all works.
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You may enjoy this video about the old boiler to new boiler conversions and how the concept of pumping away from the expansion tank was introduced in the 1960s and why it took so long to get it to become the normal way to do things.
https://www.youtube.com/watch?v=awxeWBxC4Aw Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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If the boiler air separator and scoop built in to the boiler works properly the airtrol fitting on the tank should solve the problem of air migrating out. I don't see why you would need to upsize it to 3/4". the airtrol fitting significantly reduces the water circulating by gravity in and out of the tank. As that circulation happens it takes dissolved air with it.1
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There is debate about leaving the feed to the prv open all the time but you definitely need it open when bleeding the radiators or the pressure may go down too much to push all the air out.1
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I recall looking at the install instructions for that tank fitting.
The 3/4" size was because the water within that pipe was counter flow.
The warmer would rise up along the upper portion of the horizontal then enter the tank and give up it's air.
As the tank cooled the denser water would flow back to the system thru the lower portion of the pipe.
The slope up of the piping was to insure the counter flow gravity of the water.
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@OldBoiler65 - My system has some similarities with your situation:
- converted gravity system
- steel compression tank
- air accumulation at top of system (until this year).
- pumping away
- external air separator
When I added the ATF-12 I followed the instructions as best as I could.
So I have a vertical run of 3/4" pipe from the air separator transitioning to 1" for the horizontal run to the tank, which is pitched appropriately.
At the tank it transitions back to 3/4" to connect to the ATF-12 installed at one end of the tank.
There is a second tapping in the center of the tank, which I use to charge the tank pressure with a Schrader valve (photos).
In your case I don't think the vertical runs are an issue, but the horizontal runs should be 3/4" minimum and pitched appropriately to allow adequate space for the flow of warm / cold water between the system and the tank. You should probably also pipe the connection from the "Eliminaire" as documented in the instructions.
Finally, that is one big tank, I would feel uncomfortable supporting it with just those three straps.
Eric Peterson
2 - converted gravity system
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that is exactly what the airtrol tank fitting is designed to stop. that gravity circulation is how the air gets out of the tank. the water in the tank is cooler and holds more dissolved air because of charles's law. If that cooler water containing the air from the tank then falls in to the system and is heated it releases the air from the tank in to the system because it can hold less dissolved air when it is warmer. The warmer water that rose in to the tank cools and absorbs more of the air in the tank and brings more air out of the tank on the next heating cycle.JUGHNE said:The 3/4" size was because the water within that pipe was counter flow.
The warmer would rise up along the upper portion of the horizontal then enter the tank and give up it's air.
As the tank cooled the denser water would flow back to the system thru the lower portion of the pipe.
The airtrol tank fitting has baffles to reduce that gravity circulation.
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Sounds like just what the system needs. I really appreciate all the great advice. I'm hoping to get it installed soon and I'll get back here with my results.0
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@EricPeterson Thats great to hear. I was thinking the same thing. The Eliminaire feature this boiler has should be able to work well with the Airtrol. Yes, that is a 30 gal tank and I was wondering that myself. It's a little scary how much it can weigh overhead like that. The installer must have been in a hurry that day in 1965 and they used that strapping you see with what looks like roofing nails holding it to the floor joists. Its been up there 58 years that I know of so it works but I plan on redoing it.
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Thats what I was hoping and might give it try instead of draining the boiler down and redoing all the boiler to tank piping.mattmia2 said:If the boiler air separator and scoop built in to the boiler works properly the airtrol fitting on the tank should solve the problem of air migrating out. I don't see why you would need to upsize it to 3/4". the airtrol fitting significantly reduces the water circulating by gravity in and out of the tank. As that circulation happens it takes dissolved air with it.
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I have one of these Damocles' swords in my basement's floor joist bay as well. In addition to the existing plumber's strapping, I added two cut up canoe straps (ratchet strap, nylon webbing, seat belt, etc), drywall screws, and washers. Pre drill the holes for the screws. Belt and suspenders.OldBoiler65 said:
a little scary how much it can weigh overhead like that. The installer must have been in a hurry that day in 1965 and they used that strapping you see with what looks like roofing nails holding it to the floor joists.
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Use conventional pipe strapping to add more straps with deck screws to hold the tank in place more securely that is all you need if you are worried-I only have 2 straps holding my tank up.
The roll of pipe strapping is not expensive and you can use sheet rock screws if you have them.
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@OldBoiler65 Actually, you should upsize to 3/4" pipe if possible. Someone found the original Airtrol patent application and posted it here a while back. It's pretty dense reading, but one interesting point made by the Airtrol inventor in the patent text was that he found 1/2" pipe could allow a large air bubble to form that would "bridge" the pipe and not migrate up to the Airtrol and into the tank. He found that upsizing the pipe to 3/4" prevented this "bridging" of a large air bubble, so that any air bubbles would migrate up into the Airtrol. So that's why the Airtrol instructions say to use 3/4" minimum pipe.OldBoiler65 said:
Thats what I was hoping and might give it try instead of draining the boiler down and redoing all the boiler to tank piping.mattmia2 said:If the boiler air separator and scoop built in to the boiler works properly the airtrol fitting on the tank should solve the problem of air migrating out. I don't see why you would need to upsize it to 3/4". the airtrol fitting significantly reduces the water circulating by gravity in and out of the tank. As that circulation happens it takes dissolved air with it.
It probably depends on the exact geometry of your 1/2" piping whether the air bubble "bridging" phenomenon is happening in your setup, but you won't know for sure if you're avoiding it unless you upsize to 3/4" pipe, according to the guy who invented the Airtrol.
I installed an ATF-12 last month on our side-by-side dual boiler system. The 1/2" piping that was there was not pitched correctly to start with, so I bit the bullet and cut all the 1/2" stuff out and installed 3/4" pipe pitched 3-in-12 up to the Airtrol. It'll probably be next year before I know how well the system works, but after reading the patent application, I'm glad I took the time to install the 3/4" pipe.
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Alright since I've been pressed for time this week. I went ahead and installed the Airtrol with some minor alteration to the old half inch line. So far the tank isn't getting as warm as before so the Airtrol must be stopping the gravity flow from the tank. Boiler pressure looks good and not getting so much air in the radiators. But I do still have air noise in the boiler. So the air might not be completely out of the system or not getting to the tank. I am going to get the line ran in 3/4 inch pipe as soon as possible.
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I have another question about the Airtrol instructions. B&G wants you to pipe the cold water suppy into the pipe leading to the tank. My boiler has it tapped into the side of the boiler as you can see in the picture. Is there any disadvantage to this, should I move it when I install the new 3/4" line to the tank? Thanks again!
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You actually have two things you need to change, according to the airtrol installation instructions. Quoting from the instructions, line #'s 4 and 5:
4. The cold water supply must be connected to the air line to the compression tank.
5. The pressure relief valve must not be connected to the air line to the compression tank.
I don't know the logic behind those requirements, but I assume they say "must" for good reason. Also note that they say not to install a valve anywhere in the air line, because it inhibits air flow into the tank (it looks like you now have a valve on that 1/2" line near the Airtrol.) But they do say if you MUST install a valve, to install a gate valve in the vertical section of the line. We actually have ball valves on the vertical sections of our lines right where they exit the boilers.1 -
you're piped into the bottom of the boiler there, correct?
that's fine,
whether it's piped to the tank line, or the boiler vessel(which you are),
you're still having the boiler, and tank, in the same location, the PONPC,
close enough.
now, remind us,
does the circ pump to, or away from, the PONPC, (boiler and tank)known to beat dead horses1 -
@OldBoiler65 - I don't think either of those things matters during normal operation.
What I mean is that a) there should not be any fresh water coming into the system, and b) the relief valve should not be opening.
In other words neither is critical to the task at hand of keeping air in the tank and out of the system.
I would argue that the other elements (3/4" pipe pitched upwards) are more important.
But it would be good to relocate the water supply and relief valve in the future.
Eric2 -
I don't see an air bubble becoming trapped in a 1/2" pipe filled with water.1
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Oh, i know the instructions say that but i'm not seeing that happening unless the fluid is much more viscous than water.
the instructions also say something about air flowing out of the tank without the fitting but what is actually happening is that because of charles's law cool water in the tank has more air dissolved in it, that water falls to the boiler and is heated, can't hold as much air and the air comes out of solution in the boiler meanwhile when the water with less dissolved air that replaced it in the tank because it was hot when it got there cools in the tank after the system is shut off and absorbs more air in the tank. when the boiler heats the next time the cycle repeats and moves that water with its freshly dissolved air out of he tank.1 -
I can move the water supply, but I don't think I have many options for relocating the relief. I agree that it's probably not that important as making the line 3/4" and pitched upward to the compression tank. For now, I think I will just leave the supply and relief where they are.0
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Yes, supply is piped into the bottom. My circ is on the return on right side of the boiler.neilc said:you're piped into the bottom of the boiler there, correct?
that's fine,
whether it's piped to the tank line, or the boiler vessel(which you are),
you're still having the boiler, and tank, in the same location, the PONPC,
close enough.
now, remind us,
does the circ pump to, or away from, the PONPC, (boiler and tank)0 -
The date code on that ATF-12 indicates that it was made in May of 1998, curios as to where you purchased it? Certainly not new and no warranty. That expansion tank, if no one has mentioned it, is not ASME, it is a standard non-code tank with no provision for a liquid level site glass. Looks to be about 15 or possibly 24 gallons. Piping cold water make up directly into the boiler is not a good idea because of possible thermal shock or even condensation of the combustion gases. Follow the Airtrol fitting installation instructions. Close the service valves on either side the pressure reducing valve (PRV) once the system is filled. Best piping practice is to have one on either side of the PRV and a bypass. Only open them if you have done work on the system and it need to be re-pressurized. Otherwise you could flood your basement if you develop a leak. System pressure will be the static height of the piping system measured from the PRV to the bottom of your top floor radiation plus about 4 PSI to maintain a positive pressure in your radiators.
Nick Ekdahl, CPD, GPDDirector of Training & EducationDawson Company2 -
LOL. The ATF-12 I just installed came from eBay and didn't even have a date code. It looked like it had been sitting on a shelf for 50 years.0
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@nekdahl Yes that ATF-12 is "new old stock" I found it on Ebay for a good deal. Didn't look like much to go wrong with so I'm alright with the purchase. Ah, I didn't know that about the tank. Going by the original installation quote for the boiler, the contractor states that it is 30 gallon tank. It might not be and that was in 1965 so who knows. From what I've gathered on here the contractor might not have done the greatest job on the install. I can move the cold-water inlet to the new pipe to the expansion tank. I really don't want to reinvent the wheel since this boiler is old. Just want to solve the air in the system issue for now. Yes I have closed the inlet to the PRV but I did not close the one after it yet. I'm thinking it is roughly 12 feet to the upstairs radiators from the PRV. So I need to reset to 16 PSI instead of 12 PSI like the boiler manual states? Thanks, I really appreciate all the great info.0
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@OldBoiler65 The pressure of the water column is 0.43 psi per foot, so 12 ft x 0.43 psi/ft = 5 psi. Then add 5 psi for margin, and you have 10 psi minimum. So your 12 psi is fine.1
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@OldBoiler65 - use this calculator to determine the tank volume.
I just verified it with my B&G tank:
12" diameter, 48" long => 23.50 gallons (24 is what's printed on the side).1 -
30 Gallon tanks are also 12" diameter so that would make sense. You are correct that there is not much to go wrong with the cast iron construction of the ATF fittings. It becomes a problem when someone buys a "new old stock" complicated piece of equipment such as a three piece circulator from the internet which has a date code well past warranty and it fails immediately. Then, as the rep for the area, we get the phone call because the seller either flat out refuses to take responsibility (no overhead for service or warranty so much cheaper sell price) or has disappeared altogether so "caveat emptor..."Nick Ekdahl, CPD, GPDDirector of Training & EducationDawson Company1
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@EricPeterson My tank is 12" dia and 60" long so I got 29.38 gal capacity in the calculator.
@nekdahl I never thought of it that way, but I don't sell this stuff for a living. I'm a mechanic so I'm pretty confident in buying NOS parts if I can see good pictures of it. I'd never dream of trying to get a warranty on something decades old like that. But I believe you that other people will try to.0 -
Just to update you all. I finally got a chance to plumb the B&G Airtrol into my boiler properly with 3/4" pipe. It's been working great so far for a week. I'd say this has to be the best this boiler has worked since new. Thanks again for all the help and suggestions. Here is a couple pictures of how I piped it to the tank.
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You certainly got it pitched up sufficiently.
Nice job @OldBoiler65 fitting the Airtrol in with that tight tolerance.
Eric1
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