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HW Vision-Pro question (How hard can it be?)

I recently installed a customer supplied thermostat (Honeywell VisionPro TH8110u1003) and found out it didn't work due to higher than expected voltage (32.8vac). Switched out the transformer and it worked. However, I'm still getting 29 volts. It doesn't seem likely that two transformers are having the same problem. Any thoughts? I also received a call this morning that the boiler fired, hit temp, shut down and the (indoor) temp dropped 5 degrees but boiler didn't re-fire. Could this be due to the 1 cylce an hour function?

Robert O'Connor/NJ


  • Charlie from wmassCharlie from wmass Member Posts: 4,130
    CHeck the line voltage going into the tranformer

    It could be an issue with the supply voltage. If you are getting 140 coming. Transformers only dropp what they get by a factor. If they get 120 they give 24 if they get 130 they give a bit more and so on.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Robert O'Connor_12Robert O'Connor_12 Member Posts: 724

    Charlie, thanks for the quick response!

    Where do think the voltage could be coming from? They recently (2years ago) had a new panel installed, is it possible to be getting "stray voltage" from something close to it or possibly a problem on/in the panel?

    Robert O'Connor/NJ
  • Tim McElwainTim McElwain Member Posts: 4,369
    Make sure the

    transformer is a NEMA (National Electrical Manufacturers Assoc) Class II standard DC20-92 transformer. Transformers which do not meet those standards tend to have high secondary voltages as high as 32 to 35 volts. Like Charlie says monitor you primary voltage and see if it is high. Watch out if recent changes due to bad weather were done on outside transmission lines by the electric company. I had that happen one winter after a transformer was changed on a pole and four different house had line voltages as high as 132 volts. 
  • Robert O'Connor_12Robert O'Connor_12 Member Posts: 724

    The transformer is a direct replacement for the one that was there. The boiler is a WM EG with the transformer mounted on electrical plate with the plug in for the relay (which isn't used) I'm not sure if its a NEMA. I'll go an check line voltage

    Thank You!

    Robert O'Connor/NJ
  • Tim McElwainTim McElwain Member Posts: 4,369
    That sounds like

    a control center, what are the numbers on the control center? The R and C terminals are the secondary of the transformer, are there any other wires connected as you may have another transformer wired in series with that one?
  • Robert O'Connor_12Robert O'Connor_12 Member Posts: 724

    Thanks for the help Tim. I just received a no heat call from them and went over and the first thing I checked was incoming line voltage. I got 134 volts! I removed the HW Vision-Pro and installed a T-87 mercury stat and the heat is on. I put in a call to the local utility about the over-voltage problem and they will be sending someone out today.

    Thanks again for your help!

    Robert O'Connor/NJ
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