May I Install Any Brand/Type Zone Valve In 3-Zone Oil Boiler?


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Old 10-20-13, 01:31 PM
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May I Install Any Brand/Type Zone Valve In 3-Zone Oil Boiler?

I have an Oil Boiler with 3 zones (basement/1st floor/2nd floor) and the 2nd floor was 80 degrees with no circulator pump running. I guessed the zone valve was stuck open because the circulator pump was not running. Can a stuck open valve heat and entire floor to 80 degrees (45 outside) with no circulator running? The baseboards were hot with no circulator running ...not just warm.

Secondly, I installed a known good thermostat with no change and then I rotated the valve's teeth with a screwdriver and the teeth were either already rusted or I broke them. So I'm guessing I need to replace it.

The Zone Valve is an elusive "Thrush No. 91" zone valve with 6 screws for wiring on it. In my searches, I have found it's almost identical to a White-Rodgers 1311.

If I put a 3-wire Taco Zone Valve in, will that work with the wiring?

I cannot find any wiring conversion on the web, so I am thinking of sweating in the new valve myself then calling an HAVC company to wire it up correctly to save all of that labor. I just need to know if it's OK since I'd NEVER install a 3-wire Taco if it wouldn't work with the 6-wire system.

I have a photo or the zone valve I'll put up in an hour. Thank you in advance.

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Old 10-20-13, 01:37 PM
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Yes....if the valve is stuck open....the hot water will be gravity fed and keep that baseboard almost as hot as if the pump was running.

That should work in your system. The thrush is a 6 wire valve but are all 6 terminals in use ? Most likely not.
 
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Old 10-20-13, 04:53 PM
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This is a home I rent out, so I don't know if all terminals are used. I should have taken a photo.

Since the tenants don't have heat for the 2nd floor, I decided I'm going to sweat in the new zone valve tomorrow morning and then maybe call an HVAC co to wire it up, but I'd LOVE to know what to do myself.

Unfortunately, I don't know how the wires are set up to ask you all how to convert the 6-terminal Thrush to 3-teminal Taco. But what if we assume that the 1-2-3 wires are all passed from zone 1 (the 1st floor) and then passed on to the 3rd zone (the basement which was added later):

1.) How would I wire up the new 3-terminal Taco zone valve?
a.) I'm betting that one of the 3 T-stat wires would just go unused, like #4 in the diagram above (use red/white only).
b.) I know one of the T-stat wires goes to the Taco valve #1.


2.) IF there is a different zone valve, like a 5-wire Honeywell available at Lowe's, should I favor it over the Taco? ...would it be easier to wire up?
 
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Old 10-20-13, 05:20 PM
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What about this?
4-5-6 Thermostat Wires:
A) Remove #4 wire from current zone valve and do not use.
B) Take White wire #6 from T-stat and send it to the Taco #1 terminal.
C) Twist #5 T-sate wire to current #3 wires to give it 24 volts (the 24V wire that doesn't go to the T terminals).

1-2-3 Wires:
A) Attach #2 wires from current valve to #2 on Taco.
B) Attach #1 wires from current valve to #3 on Taco.

Without knowing the theory for all of this; that's my best shot. Would it work? I know this is asking a lot! Thanks so much! -Tony
 
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Old 10-20-13, 05:24 PM
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The three wire to the thermostat is needed if the boiler powers the thermostat clock. If you have a battery powered thermostat then only two wires are used.

Your zone valve connects the thermostat to the valve and outgoing lines inside one case. A new three wire valve will do the same thing but all wiring connections will be visible.
 
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Old 10-20-13, 05:52 PM
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I forgot to mention, it's a round Honeywell heat-only Thermostat (no batteries, just mercury).

Regretfully, I don't understand most of your reply PJ ...but thank you for responding.
 
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Old 10-20-13, 06:15 PM
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Since you have the old style t'stat then only two wires are needed like you thought. The third wire would be the power for the clock which you don't have or need.

You've described the way it needs to be wired. Thrush made those connections inside the case. That's why there are 6 terminals. Less customer error. The three wire valve works the same exact way.
 
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Old 10-21-13, 05:04 AM
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So you're confirming that my wiring is correct? WOW! ...that's be great!

It's the next morning and I'm going over to the house to plumb in the new zone valve. I will set up the wiring as described above and hopefully I will not need to call and HVAC Co. to correct my wiring. I may be back with another wiring question if it doesn't work. Thank you.
 
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Old 10-21-13, 11:53 AM
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I installed the zone valve with no leaks ...which is usually my first hurdle. Then I wired it up as described above (by me) and the circulator kicked on when I turned on the T-stat! But then it stopped 60 seconds later. Hmmm. I had an extra Honeywell round (mercury) T-stat I brought from my own home and replaced the old (I was so convinced my wiring was correct) and it started working!

So After spending about 8 hours(!) trying to understand how the wiring works, I did the entire repair myself in about 3 the next day. Thanks for the replies.

P.S. The old Thrush zone valve was in such a tight place with an elbow to boot, I decided to just leave it in with the valve permanently open. Man that saved me 1-2 hours of reconstructing everything.
 
 

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