Air separator drawing air in? Circ pump causing low pressure leak?

FlintMich · January 13

In my shop I have hydronic floor heat. I originally installed the circulator pump after the air separator/expansion tank combo like everyone says to do but I've been getting air in the lines.

I've done countless overnight pressure tests on the system and have never found a leak. I suspected the air separator and tightened the air valve shut and ran it for a few days and when I opened the valve, very little air came out. After much testing, if I run the air separator closed and only open it occasionally to vent the system, it works fine. But if I leave it open while running it, like it's meant to be run, I end up getting more air in the lines.

I'm considering relocating the circ pump to the other side, before the boiler, in a "pumping to" scenario. I know that "pumping away" is the right way but I'm pretty frustrated. I don't want to keep running it with the separator closed because I'm not a fan of having to climb up to it to vent the system all the time and I didn't pay all that extra for that auto vent (twice - lol) just to have to do it manually - lol.

Is it possible that , with the circ pump being just beyond the air separator, it is causing a low pressure area that is causing air to be pulled in past the air valve on the separator? I've replaced the separator once and it didn't help. Any thoughts?

GGross · January 13

pictures

Jamie Hall · January 13

I presume the sequence of devices is expansion tant, air separator, pump inlet?

If that is the case, unless there is a significant restriction between the expansion tank and the air separator, the pressure at the air separator will be within a psi or so of the pressure in the expansion tank — provided that the expansion tank isn't bottomed out. You might want to check the expansion tank air pressure; it should be a pound or two below the static system pressure when the pump is not running.

hot_rod · January 13

at some point if you have a good separator the system should be 100% air free. Is it non barrier Pex in the system? Any other auto vents?

EBEBRATT-Ed · January 13

Need pictures.

Sounds like your Expansion tank is not doing its job and where is the PRV attached to the system??

FlintMich · January 13

https://forum.heatinghelp.com/discussion/comment/1834435#Comment_1834435

I'll get right on that. Thanks.

https://forum.heatinghelp.com/discussion/comment/1834446#Comment_1834446

Yes. The expansion tank is mounted directly under the air separator and the circulator is directly after them.
The tank is at the factory 12# it came with. This is a closed loop system if that matters.
The system is apart at the moment but it has always run between 12 and 18#.

https://forum.heatinghelp.com/discussion/comment/1834454#Comment_1834454

Yes, the pex has the oxygen barrier and the system will run nearly air free if I keep the air separator bleeder closed. But it's designed to run with the bleeder open. And I'm designed to not have to climb up to bleed it off. 😄

FlintMich · January 13

https://forum.heatinghelp.com/discussion/comment/1834459#Comment_1834459

No PRV on this system. This is a closed loop system in my shop. Not connected to my house water service.
I didn't think to get photos of it. I plan to take some next time I'm out there.

hot_rod · January 13

I doubt air is getting in. Or water would come out if the seal is broken?

If it is a Caleffi, or a brand made by Caleffi, you can get a check valve cap.

IMG_9421.jpeg

FlintMich · January 14

Thanks for the replies guys.
I appreciate your time and attention on this matter.
Be well.

Air separator drawing air in? Circ pump causing low pressure leak?

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