Will a Watts Auto Vent eventually bleed a zone?


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Old 01-14-09, 03:32 PM
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Will a Watts Auto Vent eventually bleed a zone?

I'm having poor flow through 1 of 3 zones. (first floor and largest loop, baseboard). I knowingly had a bad Watts Automatic Air Vent valve for way too long. It's mounted on an air scoop purge-type fitting with an expansion tank hanging below it.

I've replaced the air vent. Closed it to let it build up some air for a few hours and then opened it to normal position and it did vent nicely.

Question is do I have any hope of this clearing the air locked zone? I'm very doubtful there is a bleeder in the zone. And we're about to replace the whole system in a renovation. Is there any quick way to bleed without installing bleeders at high points in the loop. Just have to get through next 2 months.
 
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Old 01-14-09, 03:52 PM
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Auto Vent

In theory an auto vent would eventually purge the air as long as the air doesn't get trapped somewhere.

For help on how to purge your system we need pictures of the boiler & near boiler piping. A couple of wide shots & some closer up ones should do. You can post them on photobucket.com or similar site & post a link here.
 
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Old 01-14-09, 04:34 PM
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Check each end of each of your baseboard units or radiators. Is there an air bleeder valve? You need to bleed each until a water stream comes out. It may take a special tool to open the the bleeders - available at hardware stores.
Doug
 
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Old 01-15-09, 05:28 AM
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Pics and more details

Picasa Web Albums - Matt - Heating system

I've searched the 1st floor zone and find no bleeders.

To better explain "poor flow", this zone gets plenty hot for the first 20' or so. Then just dies out. by the time it gets back to the zone valve, it's room temp. T-stat is at 70 and it struggles to get above 60.

Other two zones seem to heat fine.

Also, the pressure limit valve is venting water on occasion. 5 gal bucket is 1/2 full in a week's time. That is a new condition. Went all summer with noticed venting at all.
 
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Old 01-15-09, 08:23 AM
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If your relief valve is lifting, it is likely because your expansion tank has lost its air charge. This needs to be fixed - when the relief valve lifts, eventually additional water and air is added to the system - the air will cause corrosion. What is the system pressure, hot and cold? When hot, the pressure must be getting up to the relief valve setpoint, probably 30 psi.

To pump the correct amount of air into the tank, via the schraeder valve, you'll first have to depressurize the water side of the tank. I don't see tank isolation valves in your pix, so you may have to partially drain the whole system.

I don't think that the tank problem explains the "poor flow" issue but it might be a factor.
Doug
 
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Old 01-15-09, 09:05 AM
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What is correct tank pressure?

Thanks for the insights...

The system pressure when hot is ~12psi. Not sure about cold. The relief valve is labeled as 30 psi. It surprises me that it's changing that much. (or, the pressure gauge on the boiler is not that accurate)

I depressurized to install the air vent so doing again won't be a problem.

What's the proper pressure of the tank?

And, Am I making reasonable conclusions on a zone that seems to run out of heat?

- It must be getting some flow and other zones get good heat so circulator pump must be running
- I've manually compressed the zone valve with a C-clamp and no difference (with circulator on for other zones calling for heat)

Anything else possible? Do circulator pumps slow down before failing?

Thanks again.
 
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Old 01-15-09, 01:18 PM
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If the pressure is only 12psi hot, then the relief valve shouldn't be lifting and the expansion tank may be doing its job.. It's possible that the relief valve is leaking - perhaps it's shot or maybe has some debris caught in it. You might try manually lifting the relief valve and see if the flow cleans it out. Otherwise, replace the valve.
Doug
 
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Old 01-15-09, 04:36 PM
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this zone gets plenty hot for the first 20' or so.
What exists at the point that the heat stops in the pipe? Is there an elbow where the flow turns downward to go to the next room by chance? If so, there's a good possibility that you DO have an air block there.

or, the pressure gauge on the boiler is not that accurate
I distrust gauges... before doing much else, you should verify that the gauge is correct. I agree that you need to check the air charge in the expansion tank.

You can knock together something like this using a discarded washing machine or garden hose. Screw this onto any boiler drain and read the pressure:



What's the proper pressure of the tank?
12-15 PSI , match the cold pressure of the boiler.
 
 

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