Empty expansion tank?


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Old 11-26-10, 09:15 AM
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Empty expansion tank?

I have a boiler for my radiant heat system. It has been making noises lately like it has air in the system so I thought that I just needed to drain the expansion tank. I found the tank to be empty and have watched it through heating cycles and it never has any water in it. Does this mean anything?
 
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Old 11-26-10, 09:38 AM
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What kind of exp tank do you have? Bladder type (looks like a BBQ propane cylindar) or conventional steel (usually hangs from joists above the boiler)

Photos would help us - please identify the valves or fittings you used to drain the tank. http://forum.doityourself.com/electr...your-post.html
 
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Old 11-26-10, 09:45 AM
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How do you know it never has water in it?

Find the temperature and pressure gauge on your boiler and tell us what BOTH temperature and pressure readings are.
 
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Old 11-26-10, 12:30 PM
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Sorry, can't get the pics up yet. I will later. Temps and pressures are good (13-14psi / 120-160 F). It's a conventional 12" steel expansion tank with an Airtrol Tank Fitting. The tank is not secured 100% so I can wiggle it a little, tap on it, feel the weight, etc. and it is close to empty if not completely empty. It is definitely not the 2/3 that I have read about in ATF literature. I guess I just want to make sure the water level is correct and am wondering if it is as easy as turning on the water supply and cracking the ATF vent until water comes out?
 
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Old 11-26-10, 01:55 PM
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Before we can tell you the proper way to do this, we should wait for photos showing the tank and all the piping and valving around it.

Your reported range of pressures and temps are a little ambigous. What would be most helpful are the pressures and temps for two separate conditions:

1. with the boiler and system hot, at whatever maximum temp you observe.

2. with the boiler and system cooled down to room temp.

Don't do any more tank adjustments before we can understand better what is going on. It's difficult to guage the water level in the tank by tapping on it or by lifting one end - I have tried, and can't do it.

You said you drained the tank. Did you drain it from a drain valve on the bottom of the tank itself? Did water or air come out? If it was water, the tank obviously was not empty. If was air, then we need to completely drain and depressurize the tank and start over - but your photos will tell us how.
 
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Old 11-26-10, 03:44 PM
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Yes, very ambiguous...

On top of that, NEVER TRUST A BOILER GAUGE!

that's one reason we would like to know the pressure @ temperature... not a 'range'. As Mike says, two readings both hot and cold are best.
 
 

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