Some Questions on Air Separators

Users who are viewing this thread

wwhitney

Well-Known Member
Messages
5,237
Reaction score
1,321
Points
113
Location
Berkeley, CA
Hello,

I'm installing a hydronic system for the first time, and have a couple questions on the air separator. The system uses a reverse cycle chiller (chiltrix.com) rather than a boiler, but I figure the hydronics are comparable. I installed this air separator: https://www.supplyhouse.com/Webstone-H-72004-V-1-MIP-Vertical-Brass-Air-Separator

1) Once I get the system filled and pressurized and most of the air out, I understand the air separator will continue to help remove any dissolved air. The air accumulates at the top of the air separator, pushing down a float. Then when there's enough air to push the float down far enough, a vent valve opens and releases most of the air. So in a closed system without makeup water, that air release will cause the pressure to drop.

Is that all correct, or have I got some of the details wrong? If the pressure will drop, is there a procedure for manually introducing more pressurized water at the purge and fill valve without introducing more air? I have this purge and fill valve: https://www.supplyhouse.com/Webstone-48614-1-IPS-Purge-Fill-Full-Port-Forged-Brass-Ball-Valve

2) At various points of construction, I've air tested the hydronic system to check for leaks. The last time I did that the pressure held on the timescale of minutes, but bled off on the timescale of days. The air separator was installed for that test. Is that the expected behavior of the air separator? Or should the air separator hold pressure during an air test, and I should look elsewhere for a slow leak?

Thanks,
Wayne
 

John Gayewski

In the Trades
Messages
2,180
Reaction score
550
Points
113
Location
Iowa
We plug the air separator during tests due to air volume changes from temperature.

Is there a reason to exclude a makeup water system? It can help protect your pump. If you want to limit the amount of automatic water makeup there are systems that will automatically pump from a reservoir in the event of a pressure drop.
 

wwhitney

Well-Known Member
Messages
5,237
Reaction score
1,321
Points
113
Location
Berkeley, CA
Is there a reason to exclude a makeup water system?
Not that I'm aware of, just that this is my first hydronic system, and the Chiltrix manual doesn't show or suggest one. I'll ask the manufacturer about it when I talk to them for the commissioning.

Thanks, Wayne
 

wwhitney

Well-Known Member
Messages
5,237
Reaction score
1,321
Points
113
Location
Berkeley, CA
You can just use a transfer pump to manually add.
Right, just wondering if there's a procedure for hooking up the transfer pump to the fill valve that will avoid trapping any air, which would then get introduced into the hydronic system once I open the fill valve.

I can imagine getting stuck in a cycle where adding water to raise the pressure also introduces enough air that the air separator eventually triggers, releasing the air and the pressure. I have no experience with this, so perhaps this is a theoretical issue that isn't a problem in practice?

Cheers, Wayne
 

John Gayewski

In the Trades
Messages
2,180
Reaction score
550
Points
113
Location
Iowa
Prime the pump and hose as much as you can and then leave the hose fitting loose. You'll make a bit of a mess.
 

John Gayewski

In the Trades
Messages
2,180
Reaction score
550
Points
113
Location
Iowa
I just thought back to filling a system once. Turn on the system circulator and then add to it with the transfer pump. You will have to watch the system pressure, bit that's how we'd did itlast time there was no auto fill. We started with a very low level of glycol in the system and there was a lot of air, so turning on the transfer pump didn't affect the pressure immediately as the air had to be ejected.
 

Fitter30

Well-Known Member
Messages
2,598
Reaction score
402
Points
83
Location
Peace valley missouri
Just over fill the system 10-15 lbs it's easier to remove a little than add. What brand and type and % glycol are u using?
 

wwhitney

Well-Known Member
Messages
5,237
Reaction score
1,321
Points
113
Location
Berkeley, CA
Just over fill the system 10-15 lbs it's easier to remove a little than add.
That makes sense, but I'm not sure I understand the operation of the air separator properly. Does it accumulate a significant amount of air, and then burp it all at once? Which would cause a big drop in pressure, I would expect. Or is it fine grained, able to release just a little air and not drop the pressure much?

What brand and type and % glycol are u using?
I'm in a mild climate with basically no chance of freezing, so I'm tempted to use 100% water. [Plus Hercules "Sledgehammer Universal Corrosion Inhibitor" as the reverse cycle chiller has a built in cast iron pump, although everything else in the system is stainless, copper and oxygen-barrier PEX, to my understanding.] But I'm thinking maybe it's safer to use 20% propylene glycol just in case.

Thanks,
Wayne
 
Last edited:

wwhitney

Well-Known Member
Messages
5,237
Reaction score
1,321
Points
113
Location
Berkeley, CA

John Gayewski

In the Trades
Messages
2,180
Reaction score
550
Points
113
Location
Iowa
The air separator catches air bubbles in a screen mesh. The air rises to the top. The "needle" losses force from the water that had been holding it on its seat and falls a little, that lets the air out as it comes. It does have to be enough air to relieve the force of the water. But when three air escapes water comes right behind it and pushes it back up onto its seat.

Like a vaccum breaker.

Different air separators work a little differently but that's the jist.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks