gurgling hydronic zone


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Old 02-03-06, 11:31 AM
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gurgling hydronic zone

Good afternoon! On the second floor of my house (zone 2) the hydronic radiator pipes gurgle and heat poorly. Takes 5 to 10 minutes after the circulator starts to warm the pipes. I also notice that when the circulator is on and water is flowing through the zone (I can hear the gurgling and feel the pipe get warm), if I open the "bleed" valve I get a few bubbles but water never shoots out, even if I leave the valve open for 10 minutes or more. (I'm no expert but it seems water should eventually come out of the bleed valve if the water is circulating.) System pressure shows 20-25 psi at the furnace, with 40psi domestic from the mains.

Zone 1 (first floor) never has this problem.

Can someone diagnose the zone 2 poor heating situation from this and recommend my next step? Thanks!

Tom
 
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Old 02-03-06, 02:23 PM
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How accurate is your pressure gauge? If you have 20-25psi and you open a bleed valve, water is going to be coming out unless somehow that circuit has been closed off. Bizarre...

Is that an auto-vent you are calling a bleeder valve? If so, it is designed to only let air escape - not water. Is there air trapped further on in the branch that you aren't successfully purging?
 
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Old 02-03-06, 02:50 PM
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Hi - thanks for the reply.

I agree on the bizarre aspect!

"Is that an auto-vent you are calling a bleeder valve? If so, it is designed to only let air escape - not water. Is there air trapped further on in the branch that you aren't successfully purging?"

The "bleeder" I meant is the screw-cap on the second floor pipe; you unscrew the cap and see a small hole with a rubber washer surrounding it. The bubbles come out of the hole when I remove the cap when the circulator is running.

There is an auto-vent on the pressure tank, and the psi gauge seems to reflect added pressure if I manually add a bit from the auto-fill valve. I'm just puzzled why the first floor (zone 1) yields spurts of hot water when I open the bleed cap on the first floor, but I get no spurts (only bubbles, and definitely no"hiss") on the second floor bleed cap. It's as if the zone 2 pressure is much less than zone 1.

Argh.
 
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Old 02-03-06, 06:11 PM
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Bleeder

I believe what you are looking at is an automatic air vent of some sort. Auto vents are not the most reliable devices in the industry. I suggest you go to your local plumbing supply house & purchase a manual bleeder. To install it, you will need to drop the pressure on the system to or near zero. Once installed, repressurize the system to about 15#, & try bleeding the air via the newly installed bleeder.
 
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Old 02-04-06, 03:29 AM
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Thanks for clarifyiing the "auto vent" - you're right, that's exactly what I was opening to "bleed" the zone 2 pipe. Sure is tough for me to describe those pesky vents and valves in words! I'll replace with a manual vent and bleed manually. I thought when you unscrew the small cap you were bleeding the line. Just out of curiosity, what is the purpose of unscrewing that small cap?

I'll drain zone 2 down to 0 pressure, replace the vent, then close the drain valve and manually open the auto-fill valve at the boiler.

Is there a "how to do this" thread here on draining and re-filling the system?

Thanks!

Tom
 
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Old 02-04-06, 07:23 AM
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Replacing vent

The purpose of the cap is twofold. First, it is to prevent air from being sucked in when the system pressure is down for any reason. Secondly, it is to stop a leak should one occur & they often do. In normal operation, the cap should be left loose 1-2 turns to allow venting.

To change the vent/bleeder, you need to turn off the water & power to the boiler, manually open the zone valve for the upstairs zone, & open the hose bib either near the circulator, at the bottom of the boiler, or somewhere in the loop on which you are working. You only need to drain enough water to drop the pressure, then close the hose bib. Usually this only amounts to a gallon or so. When finished changing the bleeder, turn the water back on, bleed the air, return the zone valve to the automatic position, turn the power back on, set the thermostat to call for heat upstairs, & try it.
 
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Old 02-09-06, 08:36 AM
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success?

Grady - thanks for the details. I've replaced the zone2 auto vent with a manual valve and all seems well. Thank you!

Of course now I have a related question. When I turned the system water supply back on, I didn't hear any water flowing into the system, so I manually opened the "system auto-fill" valve until the system gauge showed 12psi. What I call the "auto-fill" looks like a small inverted cone on the pipe between the system water valve (the one with the round faucet handle) and the boiler; the cone has a small movable lever at the top. I manually opened the auto fill by lifting the lever until it was vertical, and I heard water flowing through it. I closed it when the psi read 12 (per the Weil McLain instructions I have).

Is the auto fill normally supposed to be silent? I would have thought that if I had lowered the pressure from the original 15psi to under 10 and then re-opened the pipe valve, the auto fill would have automatically opened full blast and quickly raised the pressure back to whatever it is set for (which I don't know). As I didn't hear any water I manually opened that valve with the lever.

Tom
PS - amazing how the animated icons/smilies slow down the operation of the reply feature.
 
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Old 02-09-06, 03:08 PM
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Auto Fill (reducing) valve

When the boiler pressure is near the valve setting the feeding will be slow. If there is a considerable difference in pressure, the reducing valve will feed water at a faster rate, slowing down as the pressure nears the setting. This is done to prevent water hammer. Sometimes if the reducing valve has not feeding water for a while they stick & need to have the fast fill lever operated. Usually once this is done, the valve will operate as it should.
 
 

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