3 zone hot water system, 1 zone not working

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Old 01-16-06, 08:57 PM
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3 zone hot water system, 1 zone not working

Two zones work just fine, but I recently changed to a digital t-stat in my downstairs zone. It worked fine for 2 weeks, albeit we've had moderate temperature in NY until recently. I am now not getting any heat out of this third zone. The pipe coming out of the boiler is hot, but as it nears the exit of the boiler room, the pipe cools off. I can't get the water to flow into the 3rd zone it seems and I cannot find any valves to release possible pressure. I am certain the t-stat is wired correctly, since it has worked since it was changed. I have read the forums, and i can't figure out anything that matches this problem. The pressure is at 20# and the water temp is 160 F.
 
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Old 01-16-06, 09:28 PM
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I also hear a humming or buzzing noise now in the areas where the zones work. I used to hear the crinkle of the pipes warming up, but it has since been replaced by the hum.
 
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Old 01-17-06, 05:59 AM
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Do you have one circulator for the entire system or one for each individual loop?
If you have three circulators, find the one for zone with no heat. Turn up that thermostat and touch the motor of the circulator. Be careful! It could be hot enough to quickly burn you! If the motor is extremely hot, the circulator has probably seized and needs to be replaced. If the circulator is warm or very warm to the touch, it is running, but the water is not moving much. In that case, there may be a slug of air in the piping of that loop.
If you have one circulator, find the zone valve for that loop and manually try to open the valve with the lever. If it "opens" very easily, it is already open and the next thing to check is for a slug of air.
To be sure that it is not the thermostat, pull the thermostat off of its base, disconnect the two wires and twist them together to call for heat.
 
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Old 01-17-06, 06:26 AM
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There is one circulator for the entire system. Which is running fine.
 
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Old 01-17-06, 06:29 AM
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The two zones for upstairs split off from the boiler with an expansion tank. The third zone is completely separate, but stems off the original pipe before the expansion tank. There's a zone valve on it, with an arrow marked on the valve pointing toward the direction of the third pipe. It's on the underside of the wiring box?
 
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Old 01-18-06, 05:37 PM
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So you have zone valves on each zone. Each zone valve is controlled by the thermostat for that zone. I don't understand what you mean by the third zone being completely separate.
Do you have one large (larger) pipe coming off of the boiler, (hot supply water) with the three zones being T'd off of that pipe? Is the expansion tank connected somehow to that header, between the boiler and any of the zone valves?
Check the lever on the zone valve for zone #3, with the thermostat calling for heat. Does the lever move easily to the open position, or do you have to push hard to move it?
 
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Old 01-18-06, 06:25 PM
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Yes, I have that larger pipe coming out of the boiler, all I meant was that the two zones for upstairs are T'd off from that main pipe with an expansion tank included. The third zone is also off that same larger pipe.

I've tested the thermostat that was previously installed in that zone in a different zone and it worked fine. I then rewired the connections and adjusted the wire caps leading to the zone valve making sure the wires were not the issue. I then thought that it might be that the valve wasn't opening. While the thermostat is asking for heat, the manual open slide switch was very loose, making me believe that was the issue. But after shutting the system down, the switch was tight as it should be, and I heard the whine of the valve opening. After turning the system back on, the switch again was loose, leading me to believe that the valve was already in the open position. I had purchased (but didn't install) a new motor for the zone valve, thinking that might be the issue. But now, since I think the valve is open, and no water is circulating, I'm not sure what the issue is. The problem zone pipes lead from the boiler underground to the other rooms in the basement. Since in NY we've had a bit of cold weather since Sunday, I could assume that the basement pipe is frozen, but the pressure is not rising while the thermostat is asking for heat. I have a single Taco circulator that is working fine sending heat to the other zones.

I took some of Grady's advice and tried to purge the #3 zone while all other zones were closed. I got some air out, and after a minute or so it was all water. I'm not sure if I missed a step, but the pressure reduced in my system from 20# to around 17#. I didn't know how long to purge, and I may have stopped prematurely. But the heat is still not circulating to the #3 zone.
 
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Old 01-19-06, 09:22 AM
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It does sound like the thermostat and zone valve for zone #3 are both working properly. There must be some other obstruction in the piping for that zone. Air is the most likely culprit, although it does not make sense that all of sudden a large slug of air has entered that zone (it worked for 2 weeks and then quit). I would try to do a hand over hand of the piping to see if there are any other valves in the loop that inadvertently got shut.
Next, overide the feed valve to bring system pressure up to about 27 pounds (the relief lifts at about 30 psi). If there is a vent valve at every high point, then bleed every one of them until you get a good stream of water. Otherwise, look for a shutoff valve for that loop on the return side of the boiler with a boiler drain next to it, on the loop side of the valve. Shut that valve and attach a hose to the boiler drain valve and run it to bucket with some (1/2 gal. maybe) of water in it. Keeping the system pressure up in the mid 20s range by overriding the feed regulator valve, open that drain and watch the submerged end of the hose for slugs of air to bubble up. Keep it flowing until no more air comes out, or for several minutes, whichever comes first.
Sometimes a slug of air gets into a pipe that is difficult, if not impossible, to vent off. Keep us posted.
 
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Old 01-19-06, 11:00 AM
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OK, so I've closed zone 1 and 2, and left zone 3 asking for heat. I opened the Red feed valve to increase pressure to 27#. Now the only valve I have next to the boiler drain is a hex head male adaptor, with a circular hole in the middle with a plug in it. Is this a pressure fitting? I can use a screwdriver to twist the plug but it keeps spinning. I am not sure if that is a shut off valve or not, but it's the only thing on that pipe. I could always take a picture and email it to you if you'd like.

So, you said to keep the pressure above 20# while purging? Does that mean leaving the feed valve open while bleeding the system? After trying that, the pressure stayed around 21# while I was purging the air. After a short while, all water flowed again with no air. Is it correct to leave the feed valve open again until it gets back up to 27#? I have AIM and the name is Rootin420 if it is easier.
 
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Old 01-19-06, 05:06 PM
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Rootin420

The valve you describe sounds like a cheap balancing or shut off valve. Turn the screwdriver slot until it is across the pipe. This should close the valve as much as possible. I presume this valve is between the circulator & the purge valve.
 
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Old 01-19-06, 07:20 PM
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Yes Grady it is. Can I ask a possibly dumb question?

The line that comes out of the circulator gets split into 3 separate lines, all with those cheap shut off valves, and then the purge valves. Two of the lines run upstairs, while the third seems to run into the downstairs basement. I do have 2 bathrooms upstairs. Am I looking at the right pipes for venting? What is your take?
 
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Old 01-20-06, 04:26 PM
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Rootin

It is easy to tell which pipe to bleed. It's the one that does not get hot when all zones are calling for heat. You might want to turn up one zone at a time simply so you can label each pipe individually.
 
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