Removing air from a gas fired boiler

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Old 10-07-11, 08:52 PM
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Removing air from a gas fired boiler

I have Lennox boiler with three zones and I had to replace one of the zone valves because it started leaking last spring. I attempted to bleed the system and I have successfully removed the air from the two lower zones but I can't seem to get their air out of the highest Zone. I have done this once before and I didn't have to much trouble that time. I have tried bleeding it two different ways I turned the power off to the Furnace then I connected a hose from my utility sinks faucet to the lowest zones drain valve and then I connected a drain hose to the middle zones drain valve which I ran to my sump so I could watch the water stream to know when all of the air was removed. I had all of the thermostats off and I manually opened the corresponding Zone Valves then I turned the Utility Faucet on and monitored the water coming out of the drain into the sump until no air was present then I closed the middle zones drain valve and then the lowest zones drain valve then I shut the water off at the sink. Next I connected the water supply to the Middle Zone and a drain hose to the upper zone and followed the same procedure. However when I turned the Furnace on and turned the heat on in all the zones I only had heat in the middle and lower zones. I am not sure what I should be doing with the water supply valve and its regulator while I am bleeding the air out. Here is a link to some Pics. Pictures by jsob13 - Photobucket
 
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Old 10-08-11, 08:45 AM
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I didn't see the feed regulator in the pics...

On what you are calling the 'drain valves' in picture 2 I believe, is there a 'lever' below the drain valve? Show us those valves from another angle...



I believe from what I can see in the pic that there is a shutoff valve below the drain, and those two valves together are called a 'purge station'.

Your method of backfeeding with a hose off the faucet will work... and if it's easier for you to work it that way you can continue to do that. It's not necessary though, you can usually use the fast fill lever on your feed water regulator (aka Pressure Reducing Valve) for the same purpose.

The bottom line though is that those shutoff valves beneath the drains need to be manipulated in order to force the water through the zones, instead of simply down through the manifold and right back up again. The water will always take the path of least resistance through the system ... ' become the water ' and think about where YOU would go if you were the water. Would you go up through the zone, back to the zone valve, through the other manifold, back up through the other zone, and back down to the drain? No, you would go down 2", over 2", up 2" and out...

Your method of feeding from the sink could actually purge air from TWO zones at the same time, so if you are comfortable that way, then continue...

Hook up the feed hose from the sink to the middle zone.

Hook up the drain to either of the other zones.

Manually open the zone valves.

CLOSE ( 1/4 turn ) the levers below the drain valves.

Open the drain hose valve.

Open the feed from the laundry.

The water will now be forced to take the long route through both zones and will clear the air out of the zone.
 
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Old 10-09-11, 10:45 AM
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Bleeding Air out

The valves in the photo do say purge on them. I knew that the small handle was a quarter turn valve but I was unsure on what I should be doing with them when trying to bleed the air out. So, I should have the purge valves for the two zones I am bleading closed or should all three of those be closed. Do I have to be mindful of the Boiler pressure doing it this way? Should I leave the city feed turned on during the bleeding process? Is there any chance of the boiler pressure relief letting go with this method? There is also a Watts Regulator above the Expansion Tank and I know that the device on top of it can remove small traces of air from the system but I know there is way to much air in there now for this to remove. But on one of my previous bleeding attemps water was coming out of the device on top of the Watts Regulator is that because of the air in the system or something else. Water isn't coming out of there anymore but I was just curious.
 
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Old 10-09-11, 12:08 PM
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The relief valve lets water out at 30 psi. You can shut all the valves. Then open the drain to the zone you want to bleed. Run a hose from that drain to a bucket to catch the water. Turn the auto fill to fast fill mode and this will force the air through the zone. I wouldn't let the pressure go above 25 psi just to keep the relief valve from popping. Turn off the fast fill off and open all the valves. If you pressure is too high in the boiler, use the boiler drain to bring it down.
 
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Old 10-09-11, 04:29 PM
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So, I should have the purge valves for the two zones I am bleading closed or should all three of those be closed.
You only NEED to close the one below the one you are actively draining from. Closing all three won't hurt anything.

Remember that water will ALWAYS flow from higher pressure to lower pressure... understand this concept and you will know what to do.

Do I have to be mindful of the Boiler pressure doing it this way?
ANY way you purge, you should be. What you do NOT want to do is allow the city pressure into the boiler. You can control this by the sequence in which you open / close your valves. If you always open the drain first, then the fill hose... and close the fill hose first, then the drain... you can't get excess pressure building in the boiler.

Is there any chance of the boiler pressure relief letting go with this method?
Yes, if you don't do what's above...

There is also a Watts Regulator above the Expansion Tank and I know that the device on top of it can remove small traces of air from the system but I know there is way to much air in there now for this to remove.
That Watts Regulator thing is an 'air scoop', and the device on top is an 'automatic air vent'. This setup can remove more than small traces, but the problem is that the air has to get there first! Your problem right now is that there is no flow in the top loop because it is 'air bound'. With no flow the air won't move...

water was coming out of the device on top of the Watts Regulator is that because of the air in the system or something else. Water isn't coming out of there anymore but I was just curious.
Sometimes 'gunk' gets underneath the valve in that little can... and some water will leak out. Sometimes it stops leaking, sometimes it doesn't... they aren't too expensive or difficult to change if it continues to leak.
 
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Old 10-09-11, 04:34 PM
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The method that Droo explained is what I was talking about previously...

It's not necessary though, you can usually use the fast fill lever on your feed water regulator (aka Pressure Reducing Valve) for the same purpose.
I didn't explain it any further simply because you seemed comfortable with your method, which is just fine... it does mean an extra hose though.

On your 'pressure reducing valve' ... which I was hoping you would photograph so I knew what you had... there MAY BE (not all models have them) a lever called a 'fast fill' lever. This will bypass the regulator portion of the valve and allow water at a faster rate into the system.

If you manually open your zone valves, and as droo said, connect the hose to a drain, and close the purge valve below that drain, open the drain, and open the fast fill lever, you will achieve the same thing you were doing... but with only one hose.
 
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Old 10-10-11, 07:52 PM
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Thanks NJ Trooper for all of the great information! The regulator does have a fast fill lever. The can on top of the Watts Air Scoop did stop leaking and has been fine since. I haven't tried to purge the air again yet but I will probably do it tomorrow. I also noticed that two out of the three drain valves leak a little after they are closed I think they are leaking from where the hose attaches. If I were to replace them would you recommend unscrewing them from the body of the purge station and replacing them? I saw 1/4 Turn replacements when I was at Home Depot the other day which should last longer without leaking. I also wanted to thank you drooplug for your reply.
 
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Old 10-11-11, 04:18 PM
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You certainly could replace those valves with 1/4 turn ball drains... but do they ALWAYS leak ? or do they leak for a few days after they are used and then stop ?

You of course realize that replacing those valves means draining the system again... and at this time of the year, rather than mess around draining and refilling the system, it's probably a better choice to simply pick up a few of those brass hose caps and screw them on there and at least wait for spring to change the valves. If after putting the caps on, you happen to notice a little water leaking from around the STEM of the valve, you can give those small nuts under the handle a little snug to compress the stem packing a little bit...
 
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