Taco Zone Valve Problem
#1
09-16-10, 07:50 PM
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Taco Zone Valve Problem
I have a 3 wire Taco zone valve and I'm not getting heat on that zone. The t stat is a new Honeywell type that looks like the old round ones but has no mercury switch in it. With the t stat off Circulator and boiler are off, no power on terminals 1 &2 on zone valve, resistance on manual lever. Turn t stat all the way up, 24 volts on 1&2, after 2 minutes circulator turns on but no heat, pipe 2 ft above zone valve cold after 5 minutes. I removed the power head which looks new, others are much older. There is resistance on manual switch when no heat call. I tapped on the zone valve body but no effect, also opening valve with lever with circulator running didn't get heat going either. I think the body itself is bad, what do you guys think? Thanks.
#3
09-16-10, 08:00 PM
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Originally Posted by jgalak
If you manually short the limit switch contacts, does the heat come on? If it does, it's the switch. If it doesn't, it's the boiler or the wiring.
Hmm.. I'm not sure where the limit switch is on this thing. I know there are 3 other zones and they work fine, the boiler comes on and the heat works but for some reason this zone valve isn't opening even when it's getting power.
#4
09-16-10, 08:19 PM
Most likely the limit switch then.
The zone valve has the 2 wires that come from the thermostat and 2 wires that go to the boiler (one wire in each pair may be shared). These latter two are the limit switch wires. If there's a way to short them, you can test it that way.
Alternatively, you can disconnect the 2 wires from the boiler, manually open the valve, and test for continuity with a multimeter. If the resistance doesn't change from open to closed valve, the limit switch is bad.
I don't know if you can just replace the limit switch without replacing the whole valve...
The zone valve has the 2 wires that come from the thermostat and 2 wires that go to the boiler (one wire in each pair may be shared). These latter two are the limit switch wires. If there's a way to short them, you can test it that way.
Alternatively, you can disconnect the 2 wires from the boiler, manually open the valve, and test for continuity with a multimeter. If the resistance doesn't change from open to closed valve, the limit switch is bad.
I don't know if you can just replace the limit switch without replacing the whole valve...
#5
09-16-10, 08:28 PM
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Originally Posted by jgalak
Most likely the limit switch then.
The zone valve has the 2 wires that come from the thermostat and 2 wires that go to the boiler (one wire in each pair may be shared). These latter two are the limit switch wires. If there's a way to short them, you can test it that way.
Alternatively, you can disconnect the 2 wires from the boiler, manually open the valve, and test for continuity with a multimeter. If the resistance doesn't change from open to closed valve, the limit switch is bad.
I don't know if you can just replace the limit switch without replacing the whole valve...
The zone valve has the 2 wires that come from the thermostat and 2 wires that go to the boiler (one wire in each pair may be shared). These latter two are the limit switch wires. If there's a way to short them, you can test it that way.
Alternatively, you can disconnect the 2 wires from the boiler, manually open the valve, and test for continuity with a multimeter. If the resistance doesn't change from open to closed valve, the limit switch is bad.
I don't know if you can just replace the limit switch without replacing the whole valve...
The odd thing is, I turned one of the other t stats on and the boiler and circulator were running providing heat to the other zone, I then manually opened the problem zone valve to open and I still didn't get heat on that zone. Shouldn't I have gotten heat there with the manual switch opened and the boiler running? I only have one circulator pump for all zones.
#7
09-17-10, 05:42 AM
I'm down with the air block also. If the limit (commonly called an 'endswitch') were bad, the boiler wouldn't fire and the circ would not run.
Air blocks are COMMON causes of no heat calls.
Is this zone one of the higher (upper floor) zones?
What is the reading on the boiler pressure gauge?
Air blocks are COMMON causes of no heat calls.
Is this zone one of the higher (upper floor) zones?
What is the reading on the boiler pressure gauge?
#8
09-17-10, 11:37 AM
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I must be missing something. It seems that if the zone valve has 24 volts and the end switch is turning on the circulator but I don't have heat the zone, the valve body must be stuck or frozen closed. Is there a way to tell if I have air lock or confirm the actual valve body is opening? I have a shut off below all the zone valves as well as a hose drain do hicky above each zone valve. I can check the baseboards for a bleeder valve. The zone in question is on the 1st floor just above the boiler, there is one large zone for the 2nd floor. Thanks for all the advice and patience guys.
#9
09-17-10, 12:58 PM
I don't have heat the zone, the valve body must be stuck or frozen closed.
A bubble of air stuck in the pipe is as good as a cork, or a potato chip bag.
You didn't answer the question about the boiler pressure gauge. This question is part of the initial diagnosis. It needs an answer so we know where to go with the 'fix'.
#10
09-19-10, 07:03 PM
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Originally Posted by NJ Trooper
Assuming that to be true could cause you to waste time, energy, and more importantly, money.
A bubble of air stuck in the pipe is as good as a cork, or a potato chip bag.
You didn't answer the question about the boiler pressure gauge. This question is part of the initial diagnosis. It needs an answer so we know where to go with the 'fix'.
A bubble of air stuck in the pipe is as good as a cork, or a potato chip bag.
You didn't answer the question about the boiler pressure gauge. This question is part of the initial diagnosis. It needs an answer so we know where to go with the 'fix'.
#11
09-19-10, 07:23 PM
Sparks, yer confusing me... what you are saying now is that the circulator is running, but the burners aren't firing, right?
That's a different scenario than you initially described I think...
No, bleeding a zone is not difficult, but we need to have a look at your system to tell you which valves to turn, etc...
Got a camera? Can you take pics (clear ones please, so old dudes with bad eyes can see them), set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload the pics there. Come back here and drop a link to the album so we can view the pics.
Make sure to take pics from all angles so we can see everything, and take a few from further back so we can see the big picture.
You said 25 PSI... was the boiler already HOT ? If you've got 25 PSI and the boiler is COLD, and did not fire, then there's some other problem going on.
That's a different scenario than you initially described I think...
No, bleeding a zone is not difficult, but we need to have a look at your system to tell you which valves to turn, etc...
Got a camera? Can you take pics (clear ones please, so old dudes with bad eyes can see them), set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload the pics there. Come back here and drop a link to the album so we can view the pics.
Make sure to take pics from all angles so we can see everything, and take a few from further back so we can see the big picture.
You said 25 PSI... was the boiler already HOT ? If you've got 25 PSI and the boiler is COLD, and did not fire, then there's some other problem going on.
#12
09-19-10, 07:45 PM
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Trooper thanks! I'll get some pics after work tomorrow and post them. The boiler was hot, it has dom hot water and was running a few minutes earlier. The thing is a total POS and needs to be replaced but I just bought the place and will have to limp along with it till next year if it lasts. Yes, when I turned the tstat on, on the offending zone the circulator came on after about 2 minutes but the burner never kicked on. I have 2 other zones that work fine and they do turn the burner on. I did notice some sort on bleeder caps on two 90"s that made turns up from the basement to the baseboards, they are just 90's with little drain caps on them.
