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

FlintMich

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

pictures

Jamie Hall

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

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

Need pictures.

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

FlintMich

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

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

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

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