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Wifi thermostat not working.

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on an older (20 year) Weil McLain standing pilot/w damper gas boiler-. 2 zones-Honeywell typical 4 wire zone valves run off dedicated transformer.
All works as should until I tried to add Honeywell T6 pro smart t-stat. I do have C wire and triple checked wiring is correct, even called Honeywell help and went over with them on phone from job. Told me to return T-stat and try a new one. I went home and connected t-stat to my home system and it works fine.
Anyone have any idea why it is not working on the Weil McLain

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited January 2023
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    Model number of boiler. CP number will help too. Picture of the thermostat wire connections. (they tell you take a picture of the wires before you disconnect them in the instructions when you DIY install). And a picture of your boiler to see the controls and zone valve wires, from 3 different angles in case a wire is blocked by pipe or another wire.

    EDIT

    also need to know it you are operating heating only or if you are operating a separate air conditioner with this T6 thermostat.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HomerJSmith
    HomerJSmith Member Posts: 2,511
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    What do you mean by not working? If it was wired correctly it would work, I think.
  • Brant Beach
    Brant Beach Member Posts: 23
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    I am not there to check cp# on boiler. I can never remember the designations of WM boilers CGa maybe?. It is nothing unusual. Not power vent. T-stat is for heat only no AC. My home boiler is even older. It is Burnham P204. I do have TACO zone center ZVC406 on my system with 6 zones. Heating only no AC both are natural gas. I ran a new thermostat wire to install the new wifi so i would have the C wire. There is no doubt the the wiring is correct. Red to R blue to C white to W. The slide on the T6 pro is in up position. I did try it in down position but that did not help. It is supposed to be up for one transformer system.
    Also, the T6 when connected takes us to the heat on icon but if flashes on/off and boiler never starts.
    I installed old t-stat for now and system works fine. Thank you for your input.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
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    I am not there to check cp# on boiler. I can never remember the designations of WM boilers CGa maybe?. It is nothing unusual. Not power vent. T-stat is for heat only no AC. My home boiler is even older. It is Burnham P204. I do have TACO zone center ZVC406 on my system with 6 zones. Heating only no AC both are natural gas. I ran a new thermostat wire to install the new wifi so i would have the C wire. There is no doubt the the wiring is correct. Red to R blue to C white to W. The slide on the T6 pro is in up position. I did try it in down position but that did not help. It is supposed to be up for one transformer system.
    Also, the T6 when connected takes us to the heat on icon but if flashes on/off and boiler never starts.
    I installed old t-stat for now and system works fine. Thank you for your input.

    Are you a contractor? You seem to be talking about 2 different systems here. Which one is having the problem? the Burnham or the WM?

    Since you stated WM in your initial post. lets go with that...
    What zone valves are on the problem job?
    Is there a Zone Valve Control?
    Is there a transformer only (No ZVC)?


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Brant Beach
    Brant Beach Member Posts: 23
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    Yes, 2 different systems. The Weil McLain is the one not responding to new T6. I used my home system to see if the T6 was the problem and it worked fine on my Burnham.
    Problem job has 2 typical Honeywell 4 wire zone valves. Transformer is only R & C. Operates the 2 t-stats and zone valves. They both work fine. When I tried to install T6 it went smooth until "heat on" icon never stops flashing and boiler doesn't respond. Even after waiting 5 minutes, nothing.
    I am a contractor, an old school one. I have installed the T6 on other similar boilers so I am not understanding what the problem can be. The T6 connected to my home system works fine.
    I must be missing something but I can't think of what it could be. Like I said, it all works fine with the original t-stat so????
  • HomerJSmith
    HomerJSmith Member Posts: 2,511
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    By 4 wire, you mean two wires to the end switch and two wires to the zone motor? Two yellow and two red wires? If you have a aux transformer driving the ZVs, you have it probably wired up incorrectly. Take some pics of the ZVs and transformer, etc and post them.
  • Brant Beach
    Brant Beach Member Posts: 23
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    Yes 2 red 2 yellow. Would they have to be wired differently to add T6? I never had to do that before.
    the reds are end switch to TT on boiler and yellows are t-stats to ZV motors. Have worked as wired for 20 years.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited January 2023
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    @HomerJSmith, This guy may have wired everything correctly but just reversed the W wire and the C wire connection to the Yellow Wires on the V8043E1012. (or the TH and TR terminals on the V8043F1036)

    When there is no Zone Valve Control you often get professional wiring that looks like this: which makes it very easy to select the wrong wire.
    Looking at this diagram, you would think that Z on the Aquastat relay is Common because internally B2, Z and the relay coil are all connected to the transformer while Tv is connected to the other side of the transformer, making that the assumed R terminal. when Tv is connected to T by the thermostat R and W terminals on a 2 wire thermostat the relay pulls in and operates the relay that closes the burner and circulator contacts to operate the boiler. Assuming that Z is the Common, the only way to wire the thermostat that needs a common would appear to be this way But that actually will not work. As far as the parts inside the control are concerned, Z is common; but for the thermostat to work the Z needs to act as the R as follows:Our professional tradesman here may just need to look at the wiring a little closer and perhaps need to do a complete rewire from scratch like this. I know I have done this in the past... more than once.

    I hope this helps @Brant Beach in solving this situation. Forget your assumptions and start from scratch is sometimes the best way to Get'Er Dun

    Mr Ed.



    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    HomerJSmith
  • Brant Beach
    Brant Beach Member Posts: 23
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    Thanks Mr. Ed. I will check the wiring carefully again to make sure it is correct. I just dont know how it operates properly except for when T6 is added. If I figure it out I will let you know what the bug is. I may just add a TACO zone control box to re-wire the whole thing and see if that solves the problem.
  • Brant Beach
    Brant Beach Member Posts: 23
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    Hi Mr. Ed. An update on t-stat saga. I ended up installing Taco zone control box, threw away all the old wiring for zones. Everything works including the new T6 wifi thermostat. Still dont know what the problem was though. ??? Thanks again for you help.
    SteveSan