Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

switching to WiFi thermostat, need to attach C wire

tmeric7 Member Posts: 14
edited October 2019 in Thermostats and Controls

I moved to a new house with 5 heating zones (plus hot water tank) on a Weil McLain oil-fired water boiler with Argo ARM-6P controls. I want to replace 4 thermostats for consistency (almost all different now) and WiFi capability. In my last house I installed a Honeywell RTH6580WF and ran a new thermostat wire (old one had only two wires). We were very happy with that, so we want to use those units again.

I am 95% confident I know what to do, but I'm looking for confirmation. Each thermostat wire has only 2 wires hooked up. I can run (or simply connect) new wire as appropriate. I just want to verify that I know where the c-wire goes and confirm that I can run multiple wires into the terminal. It looks like I should run the common wires for each thermostat into the "common" terminal on the upper-right of the control panel. Is this correct, and can I run c-wires for all four thermostats to this point?

Thank you,


  • Wellness
    Wellness Member Posts: 127
    edited October 2019
    Have you looked at how your existing thermostats are wired? It should be a simple re-termination of the red and white wires to the appropriate terminals on the new thermostats. However if your home thermostats also controls AC, you will need to wires those terminals as well. Most likely you can simply connect the new thermostats to the W and RH terminals on your new thermostat.
  • tmeric7
    tmeric7 Member Posts: 14
    edited October 2019
    The existing thermostats are for heat only and they have 2 wires, R (or Rh) and W. I want to use a new WiFi enabled thermostat that requires a third c-wire. My question is about where/how to properly attach the c-wires on the control board.
  • tmeric7
    tmeric7 Member Posts: 14
    I know what a c-wire is. The link does not provide any new information. I want to verify that the place I plan to connect it on this control board is correct (99% sure) and confirm that I can connect multiple c-wires for multiple thermostats there.
  • Zman
    Zman Member Posts: 7,375
    Yes you can just run all of them to the common terminal. You may want to wire nut them together so the terminal does not get congested.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HVACNUT Member Posts: 4,663
    edited October 2019
    Yes, ^^^, the C terminal is correct.
    On a side note, your QB-180 burner is obsolete. They weren't on the market long and for good reason. You might not be able to find replacement parts for it. Look into replacing It with a Riello, Beckett, or Carlin.
    I got scared when I saw it.
  • tmeric7
    tmeric7 Member Posts: 14
    Thank you!

    I'll look to replace the burner after this winter. Too much going on with the new house now. The home has decent pellet stove backup if the burner tries to make a fool of me on that!
  • John Abbott
    John Abbott Member Posts: 355
    My hat is off to the burner tech that kept that QB 180 running they were a poor design and haven' been sold for many years.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,787
    Nothing wrong with that burner if you know what you’re doing. Still have probably a 1/2 dozen in my customer base.
    Agreed all the specialty parts are almost impossible to get, so I pick them clean when I replace one.
    I hate the boiler more than the burner.
  • HomerJSmith
    HomerJSmith Member Posts: 1,686
    edited November 2019
    To verify, I would use a volt meter and put one lead on the R connection on the thermostat wire and one lead on the Common connection and see if I have 24V, if yes, do as Zman suggests.
    Boy, that is sure clean. It would be a privilege to work on it.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,619
    edited December 2019
    I'm guessing that you have already completed the thermostat wiring without any problems.
    I'm guessing that you have already completed the thermostat wiring without any problems. BUT if you did not complete the wiring yet... you want to be sure the R on the thermostat is wired to to the R on the zone control thermostat post, other wise you won't get the power needed to operate the thermostat. The reason I mention this is the T-T terminals on zone 5 and 6 have a white wire on the T terminal that is designated as R and a red wire on the terminal designated as W. BELOW IS CORRECT DIAGRAM
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org

  • tmeric7
    tmeric7 Member Posts: 14
    Thanks for all the comments! I didn't catch the last few of them back in the fall because homeheatinghelp.com had a bad email for me.

    Anyway, I successfully worked this out back in October. I'm at work now and I can see what all 5 of my thermostats are doing! Ed, yes, I figured that out. It helps my OCD too, knowing that R goes to R and W goes to W now.

    I revisited this post to review the burner manufacturer recommendations because the QB-180 wasn't firing Monday. My neighbor, who is a serviceman for a local company, put a new Beckett 7505 burner control on to fix it. It cost me $140 total, so I'm not sure if I should have just gotten a whole new burner, but I'm open to recommendations for next time there is trouble.

    Thanks again!
    HVACNUT Member Posts: 4,663
    You can get a Weil McLain OEM spec'd Riello F5, Beckett AFG, Beckett NX, or Carlin EZ-1.

    Throw a dart and pick one. Any one. Please. Notice I left out Wayne.

    Consider yourself lucky with the QB-180. They huffed and they puffed and the blew, as oil burners.