Hydronic Heating-Air in system

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Old 12-29-10, 07:59 AM
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Hydronic Heating-Air in system

I am very thankful for all the helpful posts on here. After spending time reading through the threads, I realized I had air in my system. The water rushing noise was getting worse. It seems that after purging the air via closed zone valves, bucket, garden hose, and the system auto pressurizing to 15lbs via working pressuring reducing valve, the system runs fine for a day, then the water rushing noise returned. From what I gather, the fresh water has a high air content, which, when heated, causes the air to separate from the water.

The American Air Purger with expansion tank on bottom and air purger on the top, seem to be the issue. The expansion tank is fine. When tapping, it "thuds" and is warmer on the top 1/2, and "pings" and is cool on the bottom 1/2. This leads me to the air purger canister on the top. It is corroded, but does not seem to have a cap on it and I can see the valve stem.

I plan on replacing the air purger canister on the top. From what I have read, I need to close off the valves on the supply side to prevent water from leaving the system, turn off the fresh water supply, bring the system to Zero pressure and then remove and replace the air purger.

My questions are:
1) will this remove the existing air in the system gradually, or do I have to purge the whole system again?
2) if i purge the whole system (all 3 zones) again, won't I continue to experience the same water rushing as the fresh water is heated and the air separates?
3) we seem to have a high mineral content in the water as the air purger canister picture denotes. How does 1 deal with that?

I know I need to install a back flow restrictor to prevent boiler water from getting into the drinking water supply. I am a bit confused as how this can happen if the fresh water supply is set to turn off at 15lbs and the valve behind it is open all the time. I know some people turn it off, mine isn't. I thought the purpose of it was to keep the pressure stable in the system.

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Old 12-29-10, 08:58 AM
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Originally Posted by UpstateNYer View Post
1) will this remove the existing air in the system gradually, or do I have to purge the whole system again?
2) if i purge the whole system (all 3 zones) again, won't I continue to experience the same water rushing as the fresh water is heated and the air separates?
3) we seem to have a high mineral content in the water as the air purger canister picture denotes. How does 1 deal with that?
#1) Turn off the water feed and turn off the isolation valve on the supply side. make sure the boiler is off so the zone valves dont open. The zones look like they are on the return. Drain boiler just enough to reduce pressure and change airvent. Open all valves and feed. Turn system on and run all zones. The air seperator will take care of the little air you introduced. You may have to bleed if a zone does not circulate but I doubt it will happen.
#2) The air seperater and vent will take care of it.
#3) Probably because it was leaking and introducing constant make up water.

No offense but it looks like your boiler was installed by a rocket scientist. I like the mirror. Why not install the boilerthe other way??? One will never know.

Relief valve should be piped within 6" to the floor.

If you lose house water pressure or do plumbing repairs and shut off the main, the boiler at 15psi is greater then 0psi at the house and push back into your potable lines. Not good!!!

Let us know.

Mike NJ
 
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Old 12-29-10, 09:07 AM
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Made me laugh. I have no idea why the boiler was installed that way. I can barely fit back there the space is so tight. The mirror works for monitoring the pressure and temp. I am off to get the Automatic Air vent and this new do-hickey called a 9AS short stop, for future replacements of the Air Vent. Will let you, and the other readers, know the results.

As far as the Relief valve goes, the maximum height of the pipe, open end where water comes out, should be within 6" of the floor? So between 1" and 6"?
 
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Old 12-29-10, 09:12 AM
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I get this:
Oops... there's nothing to see here. Either you do not have access to these photos, or they don't exist at this web address. Please contact the owner directly to gain access.
when I click your picture link.

[NEVER MIND... worked second time around! ?]

When you ask for the 9AS, they will look at you like you have two heads. Probably won't stock it, but ya never know.

When you drop the pressure in the boiler and are ready to replace the air vent, KEEP YOUR THUMB HANDY! and HAVE THE NEW ONE READY TO INSTALL WHEN YOU REMOVE THE OLD ONE... YOU WILL lose some water... you will have to work fast... cover any controls that may be damaged by water ...
 

Last edited by NJT; 12-29-10 at 05:03 PM.
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Old 12-29-10, 09:15 AM
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For Trooper. Try this

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Old 12-29-10, 09:17 AM
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One more thing... you can NOT trust that 'tap test' that you did on your expansion tank.

You can NOT check the air pressure on the tank when there is pressure on the boiler.

While the boiler is at ZERO pressure for the replacement of the air vent, CHECK THE TANK AIR WITH A GOOD TIRE GAUGE and pump up to 12-15 PSI if needed.

THEN, CHECK THE BOILER GAUGE AGAIN, and if it has risen off zero after adding air to the tank, drop it back to zero and check the tank again. Add more air to the tank if needed.

Repeat the above steps as many times as needed until there is 12-15 in the tank and ZERO in the boiler. Only then will you know that you have the correct charge in the tank... no tap test will ever tell you that.
 
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Old 12-29-10, 04:54 PM
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Peace and quiet now. I did get a strange look when I asked for the 9AS, the guy instead wanted to sell me all these separate pieces to rig the shut off. I didn't opt for that, and I am glad I didn't, the replacement was easy and took 10 minutes.

I did as described in my 1st post, shut off the zones to keep water in the system, turned off the make up water supply, opened 1 drain valve (each zone has 1), got the pressure in the system to Zero. Took off the old air separator (not a drop of water came out), installed the new 1, checked the expansion tank (fine), opened all zones, turned on make up water supply, bled the 1 zone I used to drop pressure to Zero. At that point, the system filled to 15 psi. I turned all 3 thermostats way up. I could hear air coming out of the new air separator, but still heard the water rushing sound on my 2 second floor zones. So I upped the pressure in the system by 5# using the premise that the system needed a bit more pressure to get the air to move through, let the system run while watching the pressure gauge. Once the gauge got to 27#, I shut everything down by turning back the thermostats to the desired temperature. Once the system cooled a bit, I relieved some pressure to end up with 15# at 160 degrees F.

One of the 2nd floor zones just turned on, and there was complete silence, like it's supposed to be. Again, the moderators on here are just filled with useful and applicable information. Afraid of working on the boiler when it's 29 degrees outside, not me, not anymore. Learned a ton from the posts. Thanks!!
 
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Old 12-29-10, 05:05 PM
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Good deal! Glad it all worked out for ya... stay warm neighbor!

As far as the Relief valve goes, the maximum height of the pipe, open end where water comes out, should be within 6" of the floor? So between 1" and 6"?
Close enough to the floor that you can get a container under it if needed... not too close, 1" is too close. Also, there should be NO THREADS on the bottom of the pipe to discourage one from putting a cap on it in the event of leaks... KABOOM!

I relieved some pressure to end up with 15# at 160 degrees F.
You might find later that the pressure at 160 might be a bit higher, or it might not... don't be concerned if you DO see it higher by a few PSI or so... just means that when the boiler went all the way cold at some point, the feed valve let a little water in.
 
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