Zone valve or something else?


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Old 02-13-11, 06:01 AM
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Zone valve or something else?

I have a problem with a 2 zone heating system. It was intermittingly supplying too much heat to one zone. I replaced the entire zone valve thinking that was the problem. Apparently I was wrong because after the valve was replaced the heat went up to 68 with the thermostat set on 62. I disconnected the wires from the valve and let it sit for the night. This morning I got up and the room for that zone was 59 degrees. I disconnected the wires from the thermostat and went downstairs and reconnected the zone valve. The zone valve then opened and started sending heat to the zone with the disconnected thermostat. The baseboards are now hot in the zone with the disconnected thermostat. The thermostat has a red wire and white wire running to it. The zone valves are Taco zone valves. The system is an oil fired hot water boiler, heat only system. My wife is ready to call in a professional but now it is becoming an issue of personal satisfaction for me to fix this thing. Id there a relay or something else I may be missing that is malfunctioning.
 
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Old 02-13-11, 08:19 AM
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If your zone valve is opening without the thermostat connected, there's most likely a problem with the wiring.

This is a very basic diagram of how the Taco valves are connected.



These valves open when there is 24VAC applied between 1 and 2. When the valve opens, there is a switch inside the valve that makes contact across 2 and 3. When that switch closes, the boiler fires.

The thermostat is a SWITCH. You see one side of the transformer going to #2. When the thermostat calls for heat, it closes it's switch and completes the circuit sending 24VAC to the valve.

Can you trace the wires?

Do you have a multimeter and know how to use it?
 
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Old 02-13-11, 08:56 AM
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Thank you for your reply. I have a multimeter but not that familiar with its use. The wireing is very visable but looks more like a rats nest. I am not sure why there are so many wires on my system? There is also two (what appear to be) relays wired into the system
with 4 wires going to them. I would just as well rewire the thermostats with the diagram you provided but I don't know what the purpose is of these relays.
 
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Old 02-13-11, 09:13 AM
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The problem zone is the one closest in the picture with the disconnected green wire.
 
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Old 02-13-11, 09:15 AM
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No, if you've got some other 'stuff' then you don't wanna start rewiring it.

That diagram is a 'basic' setup. Those other relay boxes might be for running circulators...

If you can get some clear pics of the setup, we might be able to help you sort things out.

Free account / Image hosting, free photo sharing & video sharing at Photobucket / upload pics there / come back here and put a link to your PUBLIC album.
 
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Old 02-13-11, 09:16 AM
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Wow... you are quick ! amazing... ask and you shall receive!
 
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Old 02-13-11, 09:20 AM
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Hang on a sec... you removed that green wire and the valve closed?

Is that the valve that was changed?

Taking that bottom wire off should only have stopped the boiler from firing. It should NOT have closed the valve.
 
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Old 02-13-11, 01:46 PM
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No, that picture was taken part way through put it back together. I can't remember if it closed when I removed the wire all the way to the left when looking at it or the one in the center. When I get back home in an hour or so I will seperate all the bundled wires and see what wires go where and repost.
 
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Old 02-13-11, 05:48 PM
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I managed to track down all the wires and attached a diagram to show wjere everything goes. I still can't figure out why the system would be wired this way. Please let me know if there is a simpeler way to run this. Other then the wireing or one of those relays I don't know why else this valve would stay open. (The problem zone is #1)


Also, the wireing seemed a little brittle so I suspect that may be part of the problem.
 
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Old 02-14-11, 05:20 AM
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Excellent... just what I needed!

I don't know why the installers felt the need to use those relays in between the zone valve and the boiler, but let's assume for the moment that they felt they had a reason...

Looking at the schematic, I'd like to clarify something first:

Is it safe to presume in the absence of terminal numbers on the valves that the GREEN wire on both valves is going to terminal #3 , and that they are drawn as 'mirror' images? In other words, Zone 1 is numbered L-R as 1,2,3 and Zone 2 is numbered L-R as 3,2,1 ?

(it really has to be so, wouldn't have worked otherwise... ever)

Here's what should happen:

When a thermostat calls for heat, the associated relay should energize and command the zone valve to open. It does this by completing the circuit to the relay coil on terminals 1 & 2. You should probably hear the relay 'click' when this happens. Compare the two zones and listen for this.

When the relay closes, it makes contact between pins 3 & 4 which energizes the zone valve.

When the zone valve opens, contact is made on ZV terminals 2 & 3 which commands the boiler to run.

-----------------

It's possible that the relay is 'sticking' closed.

To check, you can use your meter on the OHM scale.

Turn off power to the boiler, and set your meter to read OHMS. Remove wires from 3 and 4 on the relay and check across those relay terminals. When the thermostat is NOT calling for heat those terminals should be OPEN, infinte OHMS. When the T'stat calls for heat, they should go to ZERO (or very close) OHMS.

Compare Zone 1 to Zone 2 if unsure about the readings... obviously they should both be the same.

If there is NO CHANGE on zone 1 between 3 and 4 on the relay, then that relay is sticking closed.
 
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Old 02-14-11, 03:55 PM
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Thank you for helping me out with my zone valve problems.
I found out that one of the relays for the problem zone was bad. I went to several different supply stores but no one had the relay that I was looking for. I ended up just eliminating the relays now everything works great.

BTW, when did you retire from the State Police?
 
 

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