Air Locked Radiator on a 2 pipe system?

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Old 03-30-11, 02:13 PM
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Air Locked Radiator on a 2 pipe system?

Have a boiler that serves 5 zones all have a common return. 4 zones are working perfectly. The zone I am having issues with is a 2 pipe supply with each supply serving 5 radiators. I had to replace a bearing assembly on the pump for this zone. I also had to add a new #79 Auto air vent. The Auto Air vent is doing its job. However the Vent is 10 feet below and about 150-200 ft. away from the first set of radiators. When I go to bleed the radiators I noticed no water bleeding out and it seems air is being sucked in to the radiator. Any tips? Thanks
 
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Old 03-30-11, 04:17 PM
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Tell us what the readings on the temperature / pressure gauge are on the boiler.

Tell us the make/model of the boiler.
 
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Old 03-30-11, 05:11 PM
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Thermo Solution boiler. looks like a blue refrigerator. Supply water PSI into boiler is around 35. Boiler tries to maintain about 165 F and cuts off at 185 F. All 5 pumps have a shared return. There's a return manifold about 8 ft. long 4 inch diameter. All other zones are working properly. I've went to each radiator on all zones and bled them all. Each one had water right away. The zone I'm speaking of is the only one with an airlock problem.
 
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Old 03-30-11, 06:12 PM
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I'm not familiar with that boiler...

But what you mean, 35 PSI ? You sure? You should have a pressure relief valve rated at 30 PSI which would have opened and dumped water if the pressure really is 35...

no water bleeding out and it seems air is being sucked in
About the only way that this can happen is if you have very low pressure in the system.
 
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Old 03-30-11, 06:14 PM
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ThermAL Solutions?

Thermal Solutions -
 
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Old 03-30-11, 06:15 PM
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Are the radiators that are sucking air ABOVE the rest of them?
 
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Old 03-30-11, 06:23 PM
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The maximum operating pressure of this boiler is 160 psig.
Say WHAT? I'm amazed... that is MIGHTY high!
 
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Old 03-30-11, 06:30 PM
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I don't see a boiler in their product line-up that is less than 250K BTU... how big is your house? must be about 100,000 square feet to need a boiler that big!
 
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Old 03-30-11, 06:35 PM
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I am sorry I did not specify in the origional post. This is a 70 year old church. It is 3 stories tall and about 50 yards long.
 
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Old 03-30-11, 07:11 PM
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OK, that explains the size of the boiler, but what about the answers to the other questions?
 
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Old 03-31-11, 12:39 PM
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Problem solved. Pressure regulating valve clogged, and the strainer was clogged. Should've been the 1st thing I checked after installing new bearing assembly. I opened the pressure regulating valve and purged all the junk out with water. I kept the pumps off then bled all the radiators while system was filling with make up water. FYI if the pumps for the system are running it will suck air in.
 
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Old 03-31-11, 03:52 PM
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Pressure regulating valve clogged, and the strainer was clogged.
Then how did you have 35 PSI in the system?

FYI if the pumps for the system are running it will suck air in.
Not always... depends on how the system is piped, location of the pump relative to the air bleeds and the expansion tank, among others.
 
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Old 03-31-11, 04:04 PM
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apparently the guage is broken.
 
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Old 03-31-11, 04:13 PM
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Ahhh, a story that I know all too well!

The reason it was sucking air then had nothing to do with the pump running. It had everything to do with low pressure in the system.

Glad ya got it working...
 
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