I have 3-zone heating (w/ Taco 571 zone valves installed near the output of the gas furnace), and 3 times in the last 4 years the second zone (main floor) all of a sudden stays open and heat never shuts off to this one particular zone. The other 2 zones always work fine. I disconnect the thermostat wires for that zone it still stays open heats and heats. I have to disconnect terminal 1 on this valve to get the valve to close and stop heating this zone. When I connect back up terminal 1 the valve opens and heats again. When this issue occurs the temp goes from 68 (normal) to as high as 78 until I disconnect terminal 1, and wait till the temp comes down and then hook up terminal 1 again and it starts heating up again. What's most weird is eventually the valve closes on its own, sometimes 12 or 16 hours later than it should and the heat is really warm (I am in New England and the temp outside is in the 20s and 30s). This problem just happened 3 days ago (first time in 2 years) and fixed itself 2 days ago, and now it is back again so I am now having the problem again right now. Is this an intermittent stuck zone valve? It looks like all 3 taco 571 valves for my 3 valves have removable heads. Should I try to swap removeable heads to another valve to see if it is something on the valve head? Any ideas how to troubleshoot/resolve?

Your zone valve head is basically an electromagnet (solenoid), Swapping the head with a zone 1 or 3 should show you that there is an intermittent short. You should be able to buy a replacement power head (valve control) without the body. The valve itself, the brass body soldered into your manifold (the pipes that branch off the boiler) is working fine. It opens and closes. This should be an easy fix for you!

Scott- thank you for the quick response. I swapped the suspect zone head valve with #3, and now both are working properly (it's only been 15 minutes). This seems to confirm the 'intermittent short' you suggested. Zone 3 is my finished basement so I can set that thermostat at 60 degrees for the coming days and weeks and it won't be inconvenient to see if the suspect valve head connected to it will fail as it will turn on and off often, as the outside temp is 30 degrees. I will post a reply in a week to close and buy a new zone valve head if there are no more similar problems, or I will post in the next week if there is a different problem. Thanks!

I believe scott nailed it. Get that head and you should be all set.

PS. Scott, nice work here. Hope you stick around and help out at AMHD. We are always looking for folks like you with helpful advice, and of course the knowledge that you appear to hold. Take care.

Hello, unfortunately it appears the problem did not follow the zone valve head. All was fine for a couple days. However, the temperature on the main floor is now rising and up to 75 degrees. The temp outside is 31. I have disconnected and unattached the programmable thermostat from this zone to ensure the t-stat is not at fault.

I should mention there is one more variable that I probably should include. Let me mention when I installed this programmable t-stat on the main floor 10 years ago or so, it did not originally work with the Taco 571 zone valve head. I had a heating contractor come in and say it was not compatible and required a relay be installed between the new t-stat and the Taco 571 zone valve head. He installed White Rogers fan relay SPDT model 90-293Q and all was fine for 7 years or so, when this very intermittent issue started. When I first had this problem a few years ago I replaced this relay thinking it was the source of the problem but eventually the problem came back. I have the spec sheet for this if needed.

Any ideas for next steps?

Same problem here.
I figured out the actual valve is sticking open and therefore not pressing up within the power head to indicate a shut off to the boiler.
Need to replace the whole valve.
I took the head off and with a vise-grip worked the valve up and down and sprayed wd40 to loosen it up but it stuck open again today after about a month.

Quote:

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Originally Posted by ripple

Same problem here.
I figured out the actual valve is sticking open and therefore not pressing up within the power head to indicate a shut off to the boiler.
Need to replace the whole valve.
I took the head off and with a vise-grip worked the valve up and down and sprayed wd40 to loosen it up but it stuck open again today after about a month.

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Can't seem to edit my reply.
Wanted to add that the way these valves work is there is a small paraffin unit inside that heats up when the boiler calls for the zone.
It expands and presses down against the valve body, forcing it to open.

When the boiler ends the call, the paraffin heater stops, cools, and allows the valve to close with the built-in spring. (with no power it is normally closed).

Like I said, this happened to me about a month ago. I took the power head off and worked the valve up and down while spraying some WD40 in there.
It stuck open again today. 77 degrees in that zone.
Time to have the whole valve replaced.
Ugh.

Thank you for the help.

It does sound like a faulty zone might be the problem. However I think the other possible source of the problem might be the RELAY I discussed in an earlier post. Is it possible for a relay to 'go bad' ?

I have a question on this. When this problem occurs, it makes sense if the valve gets stuck open, that it would allow hot water from the boiler to rise upward (as heat rises), however, why would the circulating pump stay on (forever) ? I know the pump normally comes on if any of the zones calls for heat. However, when this problem occurs, neither of the other 2 thermostats are calling for heat. But the circulating pump stays on. That would lead me to believe that the problem for me might be in the Relay that I described in a previous post. If it was for whatever reason, malfunctioning, could it continuously result in calling for the pump to stay on?

It is 77 degrees on the main floor and 74 degrees on the top floor, and both thermostats are set at 68 degrees. So right now the problem has come back. The heat from the main floor has been rising all day into the top floor, hence why the top floor is 74 degrees. The top floor heating pipes are NOT HOT. The main floor heating pipes are boiling hot, and the circulator pump has been running all day.

So what I did was I disconnected the terminal 1 from the main floor valve head so the circulator pump stopped, then 1 waited 3 minutes, then I swapped the two zone valve heads BUT KEEPING THE WIRES CONNECTED TO THE ZONE VALVE HEADS. So, in effect, the thermostat located in the main floor is dictating the heat to the top floor, and visa versa.

What started happening soon is the circulating pump started up again, and the top floor heating is on, which hasn't been on all day.

This tells me that the problem followed the electrical connection which now is connected to the top floor valve, not the mechanical plumbing valve for the main floor. I took off the thermostat which is now responsible for heating the top floor so the RED and WHITE wires are not connected to anything, and the circulating pump is still on. As soon as I disconnected the #1 terminal on the top floor zone, the circulating pump stopped.

So I think the relay or the wiring is faulty. I don't see any wires disconnected so that would make me think it is the relay.

I am thinking of purchasing another RELAY and just replacing that as my next step.

Are there any voltage tests I can do? I do have a multi-meter however if there are tests you suggest, when you say 'measure the voltage', if you could be explicit of what I should be connecting the RED and BLACK leads to, that would be very helpful.

I welcome any feedback agreeing with me or disagreeing. I really would rather not have a plumber replace a zone valve if it is not at fault.

I'm not following the whole story here, really tired from all the snow!! But, relays do go bad. With the thermostat calling for heat (turn it way up), you can test for 24ish AC volts at the zone valve between terminals 1 and 2. Are wires connected to terminal 3? If you are not getting 24~28 volts AC your relay could be a problem. Your relay should cost you less than $10.00. Good luck. Hope I've been helpful.

OK thanks. Yes I am using all 3 terminal on the valve head. Before I did that voltage test, since I am experiencing the problem of heat always staying on on that valve 1, I had previously disconnected wire 1 from terminal 1 to get the circulator to stop, so wire 1 is NOT connected to terminal 1 right now. So, I tested the voltage between the wire that is normally connected to terminal 1, and terminal 2, and it is at 48 - 50 VAC (not 24 VAC). This is with the t-stat way down. So with this problem now in effect, terminal 1 stays at 48 VAC even though the t-stat is not calling for heat. I then connected wire 1 to terminal 1 and sure enough the pump started up again even though the t-stat was not calling for heat.

Then I was looking around near the Relay that is mounted high in between the floor joists in my basement above the boiler near the hot water heater with lots of pipes and wires to check the wiring at the Relay, I accidentally dislodged the wire that connects to terminal 1 but I dislodged it at the relay end by mistake. When I went to connect it back to the terminal end of the Relay, I noticed I had 2 choices right next to each other to connect it back (the relay is white rodgers model 90-293Q enclosed fan relay). If I connect it to the end closest to the end of the relay I noticed it was at 48 VAC with the t-stat off. So I instead connected it to the bottom center male connector (right next to the other one), and I noticed it was at 0 VAC.

Now when I turn up the t-stat it changes to 48 VAC between terminal 1 and 2, and the pump comes on as expected. I then did a bunch of tests turning the t-stat up and down and sure enough the VAC went to 48 when the t-stat was turned up, and then down to 0 when the t-stat was turned down, and the pump turned off as expected. So all is working fine now.

Could it have been that the wire 1 that is connected to valve head terminal 1 was connected to the wrong connection on the Relay all along? This problem I have, only has happened 15 times or so in the last 4 years so it was never repeatable so I am not sure what the function of that terminal lead near the bottom right corner of the Relay.

The spec sheet for the White Rogers relay family 90-290Q through 90-295Q (mine is 90-293Q) can be found at http://s3.pexsupply.com/product_file...20Brochure.pdf

So things are fine now but I've said that before and only time will tell.

Also, should I be concerned that I am reading 48 VAC on a relay that says is rated for 24 V ?

Thoughts?

As I remember your zone valve should be rated at 24 volts ac +-, I think you may be taping off the wrong screw of your transformer. Check it out. I doubt your transformer was improperly sized to start with. I didn't follow the part of terminal one being disconnected, then you connect it, and the pump turns on without the thermostat calling for heat? This sounds like a short in this thermostat or its wires. If this is helping, click the icon to give me props.

Scott, this info is very helpful - thanks for the timely help. When I have the issue, yes, the pump turns on even when the t-stat is disconnected. And also when I have the issue, the wire connected to terminal 1 on the valve head (the outermost terminal) is at 48 VAC in relation to terminal 2 (the middle terminal), even if the digital t-stat is disconnected (the analog multimeter is set at a 250 VAC scale and it reads about 50 V, which is about 20% of the way).

I haven't had the issue since our work last night, so I'll give it a week to see if we are good.

This brochure explains how the Taco valves work.
By reading this I figured out why my boiler and circulator would not turn off (valve stuck open).
I know your relay issue may be resolved but this is a good read anyway since you have the valve installed. Always helps to understand how they work :)

http://s3.pexsupply.com/manuals/1350..._PROD_FILE.pdf

Ripple - thanks for the document. This is super helpful! Something tells me I might not be done with my heating saga, so this will come in as extremely helpful. Thanks to both you and Scott.