Air in system
Hi everyone, coming from Reddit where my question wasn’t answered, but saw someone suggest posting here. Thank you for your service!
I have a Burnham Series 2 hot water boiler with two circulators, a Spirovent air separator, and an expansion tank connected to cast iron radiators throughout my house and a line of baseboard heating in one room, all as a single-zone system. One of my cast iron radiators, the largest one in my house, hasn’t been consistently heating since we’ve moved, so a month ago, I put a new valve on it, hoping that would fix the issue. Things have been not working quite right since.
In order to change the valve, I drained the whole system. Refilled it. No leaks. Heated great. After a couple cycles, it stopped heating. Went around my house and bled all the radiators. Worked ok again for a few cycles, then stopped heating. Bled the radiators again. Same thing.
Someone suggested cleaning the air separator. There was corrosion on the vent part. As soon as I opened it and pulled the core out, it disintegrated in my hands. Bought a new core and cap (in case I damaged it taking off). Same thing. Everything heats up as it should, radiators get hot, then a few cycles later, inconsistent heating and bleeding again.
I’m at a loss at this point. The system sits at 12psi when cold. I topped off the expansion tank to 12psi. I bleed from first floor to second floor (though I can’t bleed the baseboard part). Yet I still have air in the system.
Any ideas what might be going on? What else should I try? I have found no evidence of leaks and the system holds 12psi without needing to top up water (from the automatic fill valve, from what I can tell).
Thank you again!
Comments
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" hasn’t been consistently heating since we’ve moved, so a month ago, " So you only have a Month of history with this home ?
Anyway since the system is pressurized I doubt much new air is coming in. If every time you bleed the radiators you get air out I say you are not done bleeding, some systems are tough to get all the air out.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
cast iron radiators? A small bleeder up top.?
Odd that the copper spiro element had dissolved. Did the system ever have glycol in it?
A recent problem like yours, posted here, needed a hose connected to the top of the radiator to get adequate flow to push all the air out.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
One of my cast iron radiators, the largest one in my house, hasn’t been consistently heating since we’ve moved, so a month ago, I put a new valve on it, hoping that would fix the issue. Things have been not working quite right since.
I read this statement this way:
One of my cast iron radiators, the largest one in my house, hasn’t been consistently heating since we’ve moved (in a long time ago), so a month ago, I put a new valve on it, hoping that would fix the issue. Things have been not working quite right since."
So I believe there is longer than one month of history here.
One of the things that comes to mind is that fact that the statement "In order to change the valve, I drained the whole system. Refilled it. No leaks. Heated great. After a couple cycles, it stopped heating." can mean something to @ajs618592 while actually not being completely filled.
I would like to understand how this "filling" is being completed.
- How many people are involved with this filling process?
- What is the water pressure on the boiler tradicator while the "Filling" is being completed.
- Are you actually getting water out of every radiator air vent before closing the air vent valve and moving on the the next radiator?
These may sound like dumb questions but you won't believe how many homeowners think that filling a radiator means letting air out until it stops, not until water comes out. This means that a radiator may only be 1/3 or 1/2 filled with 2/3 of the radiator still has air in it.
Using 2 people to fill a system is the best way to acomplish the job of Filling the system. one person watches the gauge in the basement while the other person opens the radiator vent until water spills out of the air vent. as the air leaves the boiler pressure drops and the basement person sees the gauge pressure drop and adds more water the increase the gauge/boiler pressure so there is enough pressure to get ALL the air, out of ALL of the radiators.
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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@ajs618592, you say there's two circulators, but its "all as a single-zone system." Are you saying there's only one thermostat? Indirect water heater?
As mentioned, it helps with two people and phones. Keep the pressure high but not over 30 psi to bleed. Then drop it to 12 psi cold.
I'm also a little confused why you bled all the radiators again when you only had the issue with the large one. "Heated great. After a couple cycles, it stopped heating. Went around my house and bled all the radiators. Worked ok again for a few cycles, then stopped heating. Bled the radiators again. Same thing." Why? Are the other radiators not heating now?
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Hi Ed! Nope, these are great questions. Thank you for your response.
I refilled system myself. Here was my process:
- Open all bleeder valves on all radiators.
- Allow the automatic fill valve to fill the system.
- Once water started spraying smoothly from a bleeder valve, close that radiator’s bleed valve.
- Keep going until the last radiator had water spraying smoothly from its bleed valve.
My automatic fill valve doesn’t seem to stop (it runs very very slowly, I’m thinking there’s some sediment stuck in it or something) unless I wiggle it a bit so I believe the pressure got to about 20psi by the time all the bleeder valves were shut. I then drained some of the water off from the boiler itself to get it down to 12psi.
Yes, you are correct, the problem has been happening for a while. We moved in in 2022 and that radiator has always been finicky. I know that it had been filled correctly in 2023, if I’m remembering correctly, because we had a plumber come out to close off one radiator that had a major leak (which I only discovered after tinkering because, again, uneven heating throughout the house and was trying to chase the issue—the system was long-neglected before we moved in—and didn’t really know what I’m doing [not that I know what I’m doing now haha]).
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No, sorry for being unclear. We have 4.5 years with the house, 1 month with the new radiator valve.
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The system may have had glycol in it at some point in its life, but I’m not sure. When I refilled the system after replacing the radiator valve, I added a bottle each of Boiler Liquid and Boiler & Heating Cleaner.
And yes, all radiators have bleed valves on top.
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Hi! Thank you for your response and great questions!
Yes, now I’m having multiple radiators not heating consistently, so I’m checking to see if there’s still air trapped in the system, and there seems to be, particularly for the ones upstairs.
Yes there’s one thermostat, and no indirect water heater—it’s a separate hot water tank (direct water heater? Not sure what the proper word is). No idea why there are two circulators, I think one is to push water through the baseboard heaters and one is to push water up and away from the boiler. However, it seems like they’re both running as they should (no weird noises/loud hums, I can kind of hear water flowing through them when there’s a call for heat)
My problem may be that I never got it to 30psi when refilling, only to about 20.
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