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Taco Valve Diagnostic

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ljmadness
ljmadness Member Posts: 2
in Gas Heating
Hi,
I need a little help/instruction on how to diagnose the taco valve. I have a Gas Boiler with 2 taco zone valve. Recently I replaced one of the mercury thermostat with a battery operated one. Up until before I replaced the thermostats, I believe the boiler was still getting the heating call from the valve after I turn up the thermostat. However, right after the replacement. I noticed the boiler no longer turn on after I set the temperature up manually(using new thermostat).

Couple Things that I already check:
1. Using a multimeter, when the thermostats is set to turn on, there is 24v on the 1st and 2nd terminal on the Taco Valve. When thermostats is turn off there is 0v
2. When I did the continuity test on 2nd and 3rd terminal of the same valve, there is continuity even before the thermostats is turned on which leads me to believe that something is wrong. I think there should only be continuity after 1-2mins of 24v power on 1st and 2nd terminal. There is however no voltage in terminal 2nd and 3rd, which means it is shorting somewhere, but I don't know how that is possible since I never change any of the wiring configuration. The only thing I changed is just the thermostats.

Another piece of information, after I changed the thermostats on the second floor, it was cold outside and I needed heat on the second floor, what I did was I manually opened the Taco valve and use the thermstats on the 1st floor to turn on the boiler + circulator, so the hot water will flow through both zone. I think this tells me mechanic that is supposed to open the valve is still working because I read somewhere that if the lever has resistance when I try to manually open the valve, it means the wax mechanic in the valve is broken but that doesn't seem to be the case since I can move that lever.

I guess my question is what I should check next? I am almost convinced that the Taco Valve is bad, but I want to know if there is any other things I should check before buying a new valve.

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2016
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    Did you do your continuity test of terminals 2 & 3 with no wires connected to them? If so you are correct that you shouldnt have continuity. However, if you have continuity, and the zone valve is powered (open), you're circulator should be running. Could just be wired wrong.

    There was an error rendering this rich post.

    DanHolohan
  • billtwocase
    billtwocase Member Posts: 2,385
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    Usually if the head is getting power, and not opening, it will feel warm if not hot. You said the lever will not move? may be a base issue as well
    Mike
  • ljmadness
    ljmadness Member Posts: 2
    edited December 2016
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    Thank you for the tips, I figured out the problem. Since I just bought this house, I didn't understand the setup, but basically I have a master + slave setup for the zone valve #1 + #2. Only master-zone #1 can make the heat call to the boiler. Slave-zone #2 can only be used to open zone#2 valve when I turn on the thermostats for zone#2, it can not make a heat call to the boiler.

    I guess what I don't understand is assuming I have a master-slave system setup, why did the person who set this up previously even bother to connect the slave-zone-valve terminal #3 wire to the master-zone terminal #2(or 3 I don't remember exactly which one). Wouldn't it be easier to just ignore terminal 3 since no heat call is needed for slave-zone #2 anyway.

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