Air in forced hot water baseboard system


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Old 03-16-06, 04:39 AM
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Air in forced hot water baseboard system

Help! I am new to this forum and have found it very informative. A few weeks ago I noticed a lot of sloshing in the pipes when the heat came up. I have a 3 zone system and it seemed to only affect the top floor ( 2 story house ) Figuring air in the system, I had a plumber come out and he bled the zone and showed me how to do it. It seemed to work for a day and then returned. Also started hearing sloshing in 1st floor zone. I bled all 3 zones and made sure boiler pressure was ok when hot (18 psi ) . Problem returned the next day. Have done this 3 times now. Have also noticed a slight "rattling" noise around the expansion tank when hboiler is on. Any ideas ???
 
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Old 03-16-06, 06:24 AM
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The gurus will weigh in (I'm book smart but not field smart on heating stuff), but given the rattling noise at the expansion tank, it's possible that it is waterlogged. In which case it needs to be either drained and repressurized or just replaced. There are different kinds of expansion tank and I'm not totally familiar with them. For now, it would probably help if you could identify the brand/model of the expansion tank and where it's located on your system. Might even help to take a picture and host it at photobucket or yahoo (saying that without having a clue how to actually do it!). Good luck. You could also search this forum for "waterlogged" and/or "expansion tank" and/or "diaphragm" as keywords.
 
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Old 03-16-06, 05:01 PM
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Air

Xiphias has been getting quite an education in hydronics over the past few months, unfortuneatly the hard way.
The rattling noise is, most likely, a flowcheck rattling as air passes thru it. This presumes you have flowchecks instead of zone valves. Is there any kind of air removal device, such as an air scoop, on the system? If so & there is an automatic air vent on it or on the piping, make sure the cap is loose in order that air can escape.
 
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Old 03-16-06, 06:53 PM
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Darn books. They never show what you need to know....
 
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Old 03-17-06, 03:58 AM
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Air in system

Grady - thanks for the input. There are flow check valves (2) and they are near the expansion tank. It may well have been them rattling. They have caps on the top and I will check to see if they are loose. Tanks again.

Jim
 
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Old 03-17-06, 07:06 PM
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Air & flow checks

You do not want the flow checks loose. If you do that you defeat the purpose of the flowcheck by allowing gravity migration of hot water. The caps you want loose are those on any automatic air vents. If you could host some pics of the boiler & the nearby piping & provide a link here to the pictures it would be a big help.
 
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Old 03-18-06, 05:50 AM
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Cool Air

Grady,

Thanks...after closer inspection of the check valve and some research, I did not loosen those caps. I understand that that will defeat the purpose. I found one small "bleeder" on the second floor. ( like a small petcock with a screw valve ) and some air came out before I got water, but it was no where near the amount of air that is sloshing around in the pipes. I am going to check the pressure in the expansion tank now.
Thanks again for your input.

Jim
 
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Old 03-18-06, 07:05 AM
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Air

Jim,
It often requires several "bleedings" to rid the system of air. If there was one bleeder, there is a good chance there are more but not always. If you have a bladder type tank, it will have an air valve (like on a car tire) on the opposite end from where the pipe connects. You can use a tire gauge on it to verify the accuracy of the boiler gauge.
 
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Old 03-19-06, 05:25 AM
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Air

Grady,
I checked the pressure at the bottom of the expansion tank with a tire guage and there was a little air (virtually no pressure indication on the tire guage) and then only water came out. I am assuming that the bladder is gone and my tank is no longer functioning. After another "bleeding" there is no more air in the system but the pressure is all over the place. The last air probably came from the expansion tank leaking back into the system. I guess I need to replace the expansion tank. Do I need to drain the whole system or can I valve off the zones and just drain out enough to get under the level of the tank?? Thanks again for your help.

Jim
 
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Old 03-19-06, 07:49 AM
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Ideally you should have an isolation valve for it. If you do have to drain down to that level, install a valve so you don't have to drain again 10 years from now. ;-)

Make sure the new one is pumped up to the right pressure BEFORE you install it.
 
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Old 03-19-06, 10:00 AM
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Exp. Tank

As WHO said, hopefully you have a valve between the boiler & the tank.
If you do, simply close that valve, remove the tank & install the new one after checking the pressure on the new tank. If there is no valve, shut off every valve on the boiler & boiler piping you can find, relieve the pressure on the boiler, remove the old tank, install a valve, then the new tank.
 
 

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