No power to Taco Zone Valve

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Old 10-03-14, 05:35 PM
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No power to Taco Zone Valve

Hi all,

I have an interesting issue that is driving me crazy. I have an oil fire furnace for hydronic radiant heating. The setup also has a 50 gallon tank for DHW. About 3 months ago, the water heater stopped working. The water just wouldn't get hot but they hydronic heat worked fine. The water heater itself was fairly old and leaked. I ended up getting it replaced with an on-demand electric tankless water heater. I had been quoted about $2800 to replace the oil water heater vs $1000 for the new electric water heater. I had a concern with the old tank water heater since I didn't know whether or not it had anything to do with the hydronic heating. The person that installed the tankless water heater said that the hydronic heat would work just fine regardless without the old 50 gallon tank since it was just used for DHW.

Anyway, the cold weather is starting to get here and in preparation I turned on the heat. When I turned the heat on, the furnace would still try to heat the old tank, even though it was not used anymore. I ended up closing the valves that go from the furnace to the old water heater and disconnected the thermostat from the zone valve that went to the old water heater. I also unplugged all cables from the zone valve itself..

Here is the puzzling part... I have two zones in the home, one upstairs and one downstairs. After I removed the thermostat and disconnected the cables from the zone valve that controlled the old water heater, the furnace wouldn't come on. I went ahead and cable the zone valve again (minus the thermostat). The furnace now comes on just fine and the upstairs zone works great. However, I cannot get the zone valve for the bottom floor to come on. The 24v transformer is fine since the other zone works and it gives me a 24v reading when the upstairs thermostat calls for heat.

Here is the troubleshooting for the zone having issues:

1) Turned thermostat all the way up. I can hear the thermostat click but the zone valve wont open. I check voltage between terminals 1 & 2 on the zone valve and get nothing.

2) Turned thermostat all the way up and measured 24V reading on the thermostat

3) Turned thermostat all the way down and still reads 24V (no reading on the zone valve)

4) Replaced the thermostat, still no power to zone valve

5) Replaced zone valved, still no power between terminals 1 & 2

6) Ran new wires to zone valve, turned thermostat all the way up, no power on zone valve

7) Replaced 24v Transformer

8) I can manually open the zone valve and water flows

I am not sure what else to try, is there something I am possibly missing? I've done everything I could think of as eliminating the potential culprit but still no luck. Any advice or guidance is greatly appreciated! Also, I should mentioned that the zone valve would work just fine when the thermostat called for heat BEFORE I removed the cables from the water heater zone valve and thermostat.
 
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  #2  
Old 10-03-14, 06:31 PM
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Welcome to the forums.

I've moved your thread to the hot water systems forum as this is more of a zone valve issue than a thermostat issue. Trooper will take good care of you here.
 

Last edited by PJmax; 10-03-14 at 07:43 PM. Reason: typo
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Old 10-03-14, 07:22 PM
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Tell us the make/model of the zone valves for starters............

OOps! Never mind, I read through your message and didn't see it, but there it is in the TITLE!

OK, so they're Taco valves....

Take a look at this graphic.



Compare this to your valves. Is this what you've got wired?
 
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Old 10-04-14, 03:44 PM
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Hi,

I finally got a chance to trace the wiring and it looks more like this:

Name:  ZoneValveProblem.jpg
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Should I rewire to match what's on your diagram? That seems much cleaner. The zone valve labeled as "Unused" doesn't go anywhere, it has a short copper pipe with a cap on it. My guess it was intended to be another zone? The one labeled as "Old water heater" I disconnected the thermostat going to the water heater. I don't use the water heater anymore and didn't want it calling for heat. The zone labeled "Upstairs" works fine, the one labeled "Downstairs" is the one giving me the problem.

Let me know if I need to provide more info.
 
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Old 10-04-14, 04:21 PM
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If you look at the diagram FUNCTIONALLY, you will see that it is in fact the same.

One side of the transformer going to the "2" terminals, and to one of the boiler "T" terminals.

All the "3" terminals going to the other boiler "T" terminal.

Other side of the transformer going to one side of the thermostats.

Other thermostat going to the respective "1" terminal.

What you have should work.

Fuggeddabout the 'unused' and 'old water heater' valves. I don't think they're part of the problem.

Let's troubleshoot the other two valves...

1) Turned thermostat all the way up. I can hear the thermostat click but the zone valve wont open. I check voltage between terminals 1 & 2 on the zone valve and get nothing.

NJT: As you know, you SHOULD have 24VAC between 1 & 2 when a thermostat is calling for heat.
2) Turned thermostat all the way up and measured 24V reading on the thermostat

Your thermostats are HEAT ONLY? Meaning only 2 wires, correct? You should only see 24VAC across the thermostat when it is NOT calling for heat.
3) Turned thermostat all the way down and still reads 24V (no reading on the zone valve)

4) Replaced the thermostat, still no power to zone valve

Did you re-measure the wires at the thermostat?
So, bottom line is this:

If it is wired as you have shown, and you are not getting 24 VAC to terminals 1 & 2 on the zone valve when the thermostat is calling for heat, either the thermostat is bad, or there is a broken or misplaced wire.

Have someone else look at the wiring... I know it's happened to me so many times that I look and look and look and someone else comes over and says "There it is" ! right in front of my nose.
 
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Old 10-05-14, 07:06 AM
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Thanks for the reply.

Yes, I did measure the voltage on the new thermostat as well and it always read 24v. It doesn't matter if I turn the thermostat all the way down (off) or all the way to 90F, it still shows a voltage of 24v. With zero voltage measured on terminals 1 & 2 of the problematic zone valve.

Just for kicks, I disconnected the thermostat (both terminals, the one going to the transformer and the one going to the zone valve) and connected another thermostat in the basement. I figured if it is a broken wire within the walls this would eliminate it. I still had the same issue. I measure voltage on the thermostat regardless of whether is set to 40F or 90F. No voltage on terminals 1& 2 of the zone valve.

If I were to rewire it like this:Name:  ZoneValveProblem_modified.jpg
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Do you see a problem with it? I would disconnect the zone valves not in use (Unused and old water heater), I would then jumper terminals 2 & 3 across the two zone valves that I need. I think this cabling is simpler and would make it easier to troubleshoot. Right now, there are too many wires all over the place and some are WAY too long in my opinion. Would you think it would make sense to rewire as per the diagram just to make it easier to troubleshoot and isolate the problem?

Thanks in advanced!
 
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Old 10-05-14, 07:56 AM
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Remove the wires from 1 & 2 of the zone valve that's not working and set your meter to read OHMS and measure the resistance between those terminals.

I'm wondering if there's a short circuit on the zone head... but you did say that you replace the head, correct?
 
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Old 10-05-14, 08:04 AM
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The fact that you are reading 24VAC at the thermostat whether calling for heat or not means that at this point the thermostat itself may be 'hosed'.

If in fact the coil in the zone valve is shorted, or there is an undiscovered wiring error, and the 24VAC from the transformer was applied to the thermostat terminals directly, then the relay contacts in the thermostat are probably fried... never to close again...

I was going to suggest that you jumper the wires at the thermostat together, but I don't think that's a good idea based on what we know so far. If you do that, you will either burn out the transformer, or a wire.
 
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Old 10-05-14, 08:06 AM
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Do you see a problem with it?
No, not at all. Again, it's FUNCTIONALLY the exact same thing.

There's not much point to it unless you just wish to 'clean up' the wiring a bit.

In doing so, you might just discover your problem...
 
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Old 10-05-14, 08:09 AM
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Just for a quick sanity check...

What thermostats are you using? What terminals are you wiring to on the thermostat?

The thermostats are 'set up' correctly, that is for HEAT and not in the COOLING mode... right?
 
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Old 10-05-14, 10:08 AM
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the original thermostat was a heat only. the one I replaced it with is an ac/heat thermostat, but I did make sure that it was set to 'heat'.

I ended up re-wiring as per your original diagram just to clean things up a bit, it looks much better and it is much easier to troubleshoot and work with. I am now leaning toward a bad zone valve.

after I re-cabled everything as per the following diagram;
Name:  ZoneValveProblem_modified2.jpg
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I got zero power to the boiler, normally you can hear a 'click' when you flip the power switch on. I heard nothing. I then rewired like this;

Name:  ZoneValveProblem_modified3.jpg
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I got power back and boiler came on. I then replaced the zone valve labeled 'downstairs' with the one labeled 'old water heater' and rewired with jumpers going to the 'upstairs' zone. power came back to the boiler and upstairs zone works fine. still no power to downstairs zone. it doesn't surprise me because I think the 'old water heater' zone valve was bad.

I had replaced the problematic zone valve with a zone valve I found in the original box which I assumed it was new. for all I know, may be it was bad too and I just replaced a bad zone valve with another bad one.

i'll do you agree that it is pointing to a bad zone valve? I don't think it is a thermostat problem since I know one of the thermostats worked fine before and the fact that I got no power to the boiler when I wired to that zone valve, leads me to believe it is probably shorted.

i'll go ahead and order a zone valve and then report back the results.

thanks again for all your help!

the zone valve heads are pricey!! I have about 5 zone valve heads that I don't know if they work or not, is there a way to troubleshoot them and/or make a working one out of all of them?
 
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Old 10-05-14, 11:35 AM
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If you're sure that the thermostat was calling for heat and you read 24VAC across the contacts of the thermostat, then that thermostat is probably NFG at this point.
 
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Old 10-12-14, 08:38 AM
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Thanks for all your help! You were absolutely correct, it turned out to be a bad thermostat. I had removed the original thermostat and replaced it with a thermostat I had just decommissioned from one of the bedrooms. That thermostat used to work, but it seems it did not. I went a head and bought a new thermostat and now the zone valve has power as it should and it opens as well.

I still wonder why the boiler wouldn't come on when I wired it to other zone valves. I was only able to get it to come on with one out of the 4 spare zone valves I had. So at this point I am just going to assume they are all bad.

Anyway, my problem is solved and I really appreciate all your help!
 
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