Air in the heating loop

Thetech11

hi all new on here,

I have a client with a three family house.

We can’t seem to get the air out of the one loop closed system that goes up to the 4th floor.

When we do a power purge at the boiler purge station we can and have run it for hours. The air never stops, big bubbles of air and small one. As we purge it seems more air is being created. We have tried purging with the bypass and with our same results. The home owner has limited heat.

We have put the system up from 12-28 psi with the expansion tank charged with the same, no success.
We installed an air separator spiral vent right off the supply. Pump 007e pumping away from tank on the supply line.

Don’t see a leak anywhere and the pressure seems to be holding on gauge.
Another contractor thinks it may be a kink as the 1/2 pex is not strapped in the walll up to the 4th floor and may have a belly and restrictions. They have suggested supply and return lines from the basement up to the fourth floor at a very large expense.

What can be causing all this air continuously?

Thank You

EBEBRATT-Ed

You should only need about 18psi. Higher pressure will not hurt to start with. Is this one circulator for the entire house or the 007 just for this zone?.

Your pumping away and the ex tank air side has 28psi when disconnected from the system?

Maybe put a pressure gauge on the boiler drain to see if the boiler gauge is correct.

Thetech11

I put it from 12-28 psi trying to find the sweet spot, same air, air and more air.

Yes I took the tank off the system and charged it several times from stock 12psi up to 28 psi.

Each apt has its own boiler. One loop on it dedicated 007.

I have confirmed the gauge is working with another one put on the boiler drain.

Thetech11

Ed do you think the kink in a pex line from basement up to the 4th floor would be a possibility?

I’m finding that hard to believe, the homeowner is leaning on having the 1/2 inch supply and return lines replaced with 3/4 pex to start with and if that fails to go from baseboard to baseboard.

My fear is this will all be replaced and that is not the problem.

EBEBRATT-Ed

A kink in the pex can't cause air. Does the baseboard on the 4th floor have a vent tapping you can put a gauge on?

On second thought you're pumping away from the expansion tank which is good. If the system is restricted somewhere (like a pipe kink) it would be unusual for you to be able to pull air in through an air vent. I can't see how that would be possible.

The only thing I can think of is to try and get gauges on different points in the system to figure out where the restriction is. It may take a little time and money but cheaper than repiping.

Thetech11

Thanks, I can be a drain at the end of the farthest baseboard and see the pressure. Was think of doing that anyway to try and purge form the 4th floor as a push and pull.

hot_rod

Enough of a kink or restriction can cause cavitation, which acts just like an air problem. Velocity goes way up across that restriction.

We see this at balance valves that have been choked way down.

It is one thought if this is an ongoing issue. With good air removal at the boiler and air problem should have cleared up within hours or a day of running.

Pex can mask the sound of cavitation which sounds like Rice Krispies after you pour the milk in :)

You are sure the purger is not plugged or the float inside stuck? If it is not a big job to drop pressure and disassemble the purger to see if something inside is damaged or stuck, I would start there.

Thetech11

The air eliminator is brand new spiral vent right under the expansion tank right before the circulator pump.

A watts micro bubbler was replaced thinking that we had that problem, but it didn’t know good.

but the pump is cavitating, but can’t seem to remove all the air.

Thetech11

sorry spiral vent is above the expansion tank before the circulator pump on the supply line. The spiral vent is brand new.

hot_rod

If the pump is cavitating it sound like maybe just a good power purge with a fast fill valve or garden hose connected, to get a high gpm flowrate through the system may be all that is required.

If a bubble is stuck in the pump sometimes loosening the motor mounting bolts just enough to burp it out may get the flow moving again.

The Spiro can only purge the air that makes it's way down to the boiler.

Thetech11

Hi Bob, I have don’t that with a full blast of city pressure but still have air.

Do you think I can put an air eliminator on the top floor at one of the baseboards?

We currently have two watts AAV that are new as well I we get little to no air.

I think I have tried it all, and I’m turning to this community for help of something that might not be conventional but will work.

I know I must seem like a pain in the butt, saying I’ve done this and that, but I do appreciate the time that is taken on this as I feel there must be an better option then ripping all the tubing out.

hot_rod

Do you get any air out when you do those full flow purges?

Maybe a pic of your piping and purge locations, perhaps flow is short cycling and not going through each individual loop.

Generally on the highest point in any system there is some type of manual/ auto air vent for air that migrates up under no flow conditions.

You cannot get much of an air purger in baseboard enclosures, a small manual or hydroscopic perhaps. But it is not in lieu of a proper air removal device at the boiler

Systems with low spots in the piping can be tough, but not impossible to get and keep air-free.

There is always a fix, I don't think you have a system that is unique in regards to air removal.

Thetech11

I will upload a pictures on Monday when I get back on site.

thanks again

Thetech11

Yes I do I get a ton of air that just won’t stop. I power purged it for 2 hrs. Last week and gave up as it seemed that did nothing as air was still stuck in the system.

hot_rod

Unless air is going in with the water, it has to be pushed out with sufficient water flow. On piping 3/4 and larger you need a good flow of water to push the air ahead of it, 5 gpm flow or more. Most fill valves are not capable of that unless they have a bypass around then giving you building pressure to work with.

Connecting a garden hose to a partially plugged boiler drain would have the same effect.

It still sounds like the purge pathway is not correct.

Thetech11

hello, sorry haven’t gotten a chance till today to get back to the site. Bob I did what you said, still having air, the return sounds like a cascade but no matter how much I purge all the same. I put a hose on a valve off the building and still air.

bjohnhy

An idea, probably not the issue. See photo

There is an obstruction in the pipe marked red, and the circulator is "sucking" in air from the spirovent? Seems very unlikely with a pressure >12psi

EBEBRATT-Ed

Not the problem you posted about but "A" problem is the manual reset aqastat. probe will never work in that location. Needs to be in active water not a dead ended pipe

Thetech11

Ok thanks we can address that after this problem gets fixed.

Thetech11

I capped off the spirovent in hopes that it was sucking in air. Did a purge same story. So tired of chasing this problem.

bjohnhy

Tell us in more detail, how are you introducing fresh water into the system with your purge?

You mentioned 4th floor, but how many feet above the expansion tank is the highest radiator/baseboard? is each story 15ft?

You mentioned the system was holding pressure ok (ie no leaks)? What time frame was this test done over with the supply valve closed off?

neilc

maybe cap tight the auto vent on the boiler also,

(after initial fill)

Thetech11

I have been doing the power purge by turning the boiler off, letting it cool for an hr.

Shut the white ball valve. Put a garden hose on the red valve just about hooked up to full city pressure. Bring pressure up to 25-28 psi and open the red vavle on the supply line into a bucket.

The air bubble big and small just won’t stop.

Thetech11

I have capped everything tight all air vents.

Can’t understand what is going on.!!!
homeowner had other contractors come in and they walked away not having a clue either.

bjohnhy

I am suspicious the "city" water has a relatively high air content, and when it gets relatively depressurized on the 4th floor, the air dissipates out. Potentially the building's pressure reducing valve is faulty and allowing air to ingress.

Has anyone tried to due the purge/flush using a bucket or bin of water with a pump as is done with cleaning out a tankless? This method would limit the amount of new city water is introduced in the flush process.

Thetech11

yes, this was tried a week ago. The auto feeder is not more the a couple months old as the old one was clogged with silt.

Thetech11

could auto feeds introduce high amounts of air. But have this problem when the auto feeder is bypassed and used a garden hose as well.

bjohnhy

No.

Auto feeds should not introduce lots of air. And you appropriately bypassed that with your garden hose fill and effectively ruled out the autofeed as the source. But I was referring to the the buildings separate Pressure Reducing Valve (if it has one). If the closed system was purged with separate bucket and pump ( similar to flushing out a tankless where the same water content gets recirculated this) should expel all the air introduced with city water.…if ran for enough time with strong enough pump...45minutes?

When you purged the system with garden hose, how fast do you think the water was flowing?

HVACNUT

Is that the return? Is that where you're purging from?

Thetech11

probably 10-15 gpm with the garden hose. This is the pump I was using

Thetech11

no that is the purge stn. for the next boiler over. Hard to tell but it’s this one with a white handle ball valve behind aquastat circled. Why do you see a problem here too?

neilc

so wait, 4 floors above the boiler?

what pressure is the boiler set to?

is there any venting on that top floor?

with circs off do you have fill pressure at the top?

leonz

https://forum.heatinghelp.com/discussion/comment/1878918#Comment_1878918

Yup, my first thought would have been to fill it from the 4th floor to purge it.

EBEBRATT-Ed

The fill location does not mater air rises to the top.

neilc

https://forum.heatinghelp.com/discussion/comment/1878918#Comment_1878918

disregard, I went back a read from the beginning, you got this covered,

one last dumb question, you're closing the ball valve under the purge bib, correct?

Thetech11

yes 4 th floor, my pressure with the cir off is 25. Can’t purge up top other then a couple of watts avv

Thetech11

I do close the ball valve

HomerJSmith

I use a lawn pump for filling and air removal. It has 125' head. Since I use de-mineralized water with a PH of about 8, I do it this way.

I take a 5 gal bucket fill it with treated (deionized) water, you can use street water depending upon the quality, and I put the suction hose to the pump in the bucket and the pump discharge hose to the circuit that I want to purge. I than take the return from the circuit and put that hose in the 5 gal bucket and I run the pump, adding water to the bucket as it empties. I run it until there aren't any bubbles flowing into the bucket from the return from the circuit. It works great. It takes at least 2ft/sec to remove air in a vertical pipe.

I bought my pump at Lowes. Merry Christmas, one and all.

bjohnhy

There is a Watts Auto air vent on 4th floor? And you closed that off to make sure it was not the site of air entry? Have you put a pressure gauge on 4th floor? Just brainstorming here