Bleeding air in multi zone boiler

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Old 12-22-09, 06:29 AM
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Bleeding air in multi zone boiler

My top zone is not heating but my two other zones are. I believe it has to do with air in the zone. I am planning on trying to bleed the air from the bad zone and have a couple of questions. After I attach hose to drain bid should I turn off valve under drain bib that leads to circulator? Also, what should I do with the system feeds if anything? Should I turn off the feeds to the other zones? Or should I turn off the feed to the bad zone?

Thanks in advance
 
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Old 12-22-09, 09:26 AM
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just open the bleeder screw, have a hose or rag or whatever else to catch the water when it comes out. if your only problem is air, you dont need to do anything else. Now if there is another problem, then it gets more complicated...

do you know where the air got in? that may be your other problem
 
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Old 12-22-09, 09:47 AM
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Don't know where the air got in. The system has both radiators and baseboard slat-fin type heaters. I don't think the baseboard radiators can be bled, am i right? I can't get to the bleed valves on a couple of the radiators so i am planning on bleeding the system from the boiler. If I do that is it necessary to bleed the radiators as well?
 
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Old 12-22-09, 11:45 AM
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First check the system pressure. If low then the water won't reach the upper zone(s). Typical boiler pressure is 12 psi cold (about 18 psi hot). However, this value is dependent upon how far it is from the boiler to the top most radiator (in feet). The 12 psi cold is typical for a 2-story home.

It is best to bleed air out then to purge it. When purging it a lot of fresh water is added to the system. Which can cause air issues all over again.

Al.
 
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Old 12-22-09, 01:10 PM
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Originally Posted by pvava View Post
I don't think the baseboard radiators can be bled, am i right?
You'd have to look and see if there are bleeder valves on the baseboard units.

When you say that you can't reach the bleeders on some radiators, can you post some photos? How about a long-handled screwdriver or a 1/4" female socket driver/adapter, with an extension or ratchet wrench? Or use one of the bleeder tools sold at hardware stores along with some pliers or other jury-rigged jig.

I agree with OldBoiler - purging the boiler is not as preferable, except as a last resort. And tell us your boiler pressure and temp.

How has the system been bled before? How would air have gotten into the system? What kind of air-removal device(s) and expansion tank do your have. We need more info.
 
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Old 12-22-09, 01:36 PM
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Boiler pressure is about 19psi. temp gets up to 180. There are two radiators I can't get to the bleeder valves on. To get to one of them I would have to dismantle the woodwork is a bay window It is behind a vented piece of wood. The other is in the wall and surrounded on both sides assuming the bleeder valve is to the left or right of the radiator. I did bleed the system and no luck. Maybe I didn't bleed the system enough. I am starting to think it might be the circulator. The coupler spins but it make a louder buzzing noise than the other circulators. They are all BG 100. Could this noise mean something bad about the circulator?
 
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Old 12-23-09, 07:00 AM
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Is the circulator with the buzz the one that feeds your zone with no heat?

But even so, if the coupling is rotating, the pump must be operating, buzz or no buzz. If that zone is air locked, the pump will be pumping against shut-off head, with no flow; that can cause unusual pump noise.

What type of air removal device(s) and expansion tank? Did this problem just pop up while the system was performing OK? Was the system depressurized or worked on - which is one way air could get into the system? Another way is air-entrained make-up water and non-functioning air removal.

Photos would help.
 
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