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thanks Rich, I have often thought that may be part of the problem.

Tinman, A few thoughts.

If you put the boilers in the summer or fall and bleed them, you may not have gotten out all the air that is trapped and then you pack up and leave. When the first cold week comes you may find excessive air in the system. The reason being the water traps the air and will not give it up until you reach 2oo degrees. When the water gets that high it releases the air and usually comes back to the boiler. This is problematic with slabs since you can't take the temp up that high. Therefore, check out this link and see if they may help you.

https://www.google.com/search?q=chec...w=1280&bih=839

A defective "brush" type air purger is probably what's causing this, the floats seem to get gunked up fairly easy at times.. I don't have this problem with a B&G IAS and open tank. I think I'll revise my procedures to include a intense cleaning after installation. thanks for the comments fellas.

Originally Posted by tinman

Thanks for the comments. I install sparco or spiral vent air eliminator. Sometimes caleffi or taco air eliminators. I thought (probably mistakenly) that the 18 inch straight pipe requirement was only needed on the old style bell and gosset IAS and amtrol cast iron air scoops that use a maid-o-mist type auto vent.

I thought about a leak but haven't found one. The system is in a house with a concrete floor crawl space. A leak should show up. No buried pipes other than the walls going to the second story.

Not sure if there is bleeders on the baseboards but there may be. We generally purge all the air from the boiler location with a purge pump and bucket. This system has new propylene glycol anti-freeze.

Your distance is going to depend on manufacturer and type of air seperator.
If it's a simple scoop type, then the 18" requirement is a must.
If your using a B&G enhanced air seperator (the bell looking type, that has a screen inside), then there is no distance requirement. shoot, you can come directly into the bottom of them.
Check your manufacturers instructions.

No leaks, means no makeup water (baring broken autofill).

Check you baseboards. The air is stuck in the baseboard when your purging from the boiler, and then as the boiler runs that air losens up and mixes through the system.

For some reason your air seperator isn't picking it up though, if thats the case.

I would still suggest hitting all your radiation directly.

Thanks for the comments. I install sparco or spiral vent air eliminator. Sometimes caleffi or taco air eliminators. I thought (probably mistakenly) that the 18 inch straight pipe requirement was only needed on the old style bell and gosset IAS and amtrol cast iron air scoops that use a maid-o-mist type auto vent.

I thought about a leak but haven't found one. The system is in a house with a concrete floor crawl space. A leak should show up. No buried pipes other than the walls going to the second story.

Not sure if there is bleeders on the baseboards but there may be. We generally purge all the air from the boiler location with a purge pump and bucket. This system has new propylene glycol anti-freeze.

Not saying it's happening, but never rule out the homeowner. Some homeowners believe that you have to bleed the radiators/system especially if they lived with a problem system for years. Sometimes it's just the way they were raised or found out that it worked (somehow) in the past.

I always install a SpiroVent type air remover on new installs. The minimal straight length of pipe before any air seperator is a must. The real head scratcher was over 10 years ago on an aluminum HE boiler. The antifreeze that had been installed was actually causing some kind of gas in the system due to a chemical reaction with the aluminum. The rest of the posts covered any other ways I can think of ways for air to get into a system at the moment.

What type of air separator are you using, and does it have an air vent to remove the air.
Have you tried to monitor the amount of make up water that is being used.

Originally Posted by tinman

A recent thread got me thinking about a few jobs. We install mainly lochinvar 90% boilers. We install them waccording to the piping diagram in the install manual.

Anyhoo, every once in awhile we'll get one that causes a headache with air. I have purged systems and run them and thought "man that's quiet" Then a few months later it sounds like a sewer pipe. I've poured over the factory piping diagrams to see if there was a difference from mine to theirs.

I've wondered if conditions could bring air into a system from the auto vent. TBH I much prefer a bell and gosset IAS and a open expansion tank but bladder tanks are here to stay. I've wondered if a additive like a oxygen scavenger was in order, if it even exists.

I've thought about installing a hih efficiancy air scoop on the dedicated hot water maker line. But I never know which one will be a pain.

any thoughts?

The air has to come from somewhere.

Sounds like you have makeup water coming from somewhere.
Makeup water brings air.

Look for a leak. Whats the chance that this system has a buried return?
If so, plan that it's leaking, and your feeding water in.

Next time your there, after you bleed out the air, turn off the valve to the makeup water.

If you have a leaky auto bleeder, with a pump installed incorrectly, it could pull that air bleeder into a vacuum and suck air in. But that would require incorrect piping, which you've said you don't have, plus a myriad of other problems.

Or your air seperator is installed incorrectly, and the air is seperating from the water, and not being pulled out of the system like it should. I'd assume you have a scoop, but not even close to 18" of straight pipe into the seperator, or something like that (if it's a seperator problem)

Boiler systems with air problems.

A recent thread got me thinking about a few jobs. We install mainly lochinvar 90% boilers. We install them according to the piping diagram in the install manual.

Anyhoo, every once in awhile we'll get one that causes a headache with air. I have purged systems and run them and thought "man that's quiet" Then a few months later it sounds like a sewer pipe. I've poured over the factory piping diagrams to see if there was a difference from mine to theirs.

I've wondered if conditions could bring air into a system from the auto vent. TBH I much prefer a bell and gosset IAS and a open expansion tank but bladder tanks are here to stay. I've wondered if a additive like a oxygen scavenger was in order, if it even exists.

I've thought about installing a hih efficiancy air scoop on the dedicated hot water maker line. But I never know which one will be a pain.

any thoughts?