Monday, June 20, 2011

Programmable Honeywell thermostat replacement for a Trane WeatherTron with auxillary/emergency heat

I replaced my old Trane WeatherTron thermostat with a new Honeywell programmable model to help save with the electricity and fuel bills.  The old WeatherTron was also really ugly. Having two heat sources, the electric heat pump and the furnace, seemed to complicate the setup and install of the new Thermostat. Since it took a lot research and verifying to find where all the wires from the old unit hooked into the new one, I thought it may be helpful to post the wire translation that worked for me.  Since this is a DIY project, and I have absolutely no authority on this subject, here's a disclaimer:

I AM NOT LICENSED, CERTIFIED OR IN ANY OTHER WAY QUALIFIED TO PROVIDE ANY HEATING OR AIR CONDITIONING SYSTEM ADVICE. USE OF ANY OF THIS INFORMATION MAY CAUSE SERIOUS DAMAGE. CONSULT WITH A PROFESSIONAL BEFORE USING ANY INFORMATION ON THIS PAGE.

Really, I have very little knowledge of these systems and following the information here could cause great harm to your system. I consider myself lucky that I didn't blow up my entire heating and cooling system or burn the house down. I did do a lot of research and in the end, ended up deductively determining the new wiring based on all the information I could find. To this day, I'm still not sure if it's really correct, but so far, it seems to be working with my equipment. Also, this isn't a trial and error situation. I have no idea what happens if the power is turned on with the incorrect wiring, but I assume everything would get destroyed. Also, be careful with the old WeatherTron thermostat since it contains a mercury switch.  Mercury is highly toxic and you don't ever want to be in contact with it.


Here's the setup:
  • Electric Air Conditioner with Heat Pump Converter
  • Emergency heat (furnace heat)
  • Thermostat with cooling, regular heat and emergency heat.
The old WeatherTron thermostat had a switch to toggle between "AUX." auxillary and "EMERG." emergency heat. AUX ran the electric heat pump and EMERG, the furnace (heating oil in my case). Once the outside temperature drops below about 50 degrees F. (10 deg. C), the heat pump can no longer keep up, so I switch to the furnace.






Honeywell Programmable Trane WeatherTron



I couldn't find a Honeywell Thermostat that could handle multiple multiple heat sources at the local hardware stores, so I got mine, the "Honeywell TH8320U1008 7day 3/h 2/c Vision PRO 8000 Touchscreen Programmable Thermostat" from Amazon. It's a very nice thermostat and does everything I need. I also got the external temperature sensor for mine so it can automatically switch between electric and furnace heat, but I haven't installed that yet.

Before I tried anything, I made sure to TURN OFF THE POWER AT THE BREAKER for all heating/cooling equipment and to verify that the power is off everywhere using a field tester. Leaving the power on for the swap may cause serious damage or risk of shock or electrocution. Be very careful whenever working around electricity, especially if you're like me and aren't sure what you're doing.

Here's the original wiring for WeatherTron thermostat:



And the wiring I ended up with for the Honeywell:



One last final notice before the translation table:

CALL A PROFESSIONAL.  DON'T TRY THIS YOURSELF.  I AM NOT RESPONSIBLE FOR ANY LOSSES OR DAMAGES RESULTING FROM THE USE OF THIS INFORMATION.




Wire Color WeatherTron
Terminals
Honeywell Terminals
(Heat Pump Codes)
Red R R
Brown/Tan T * - Leave disconnected
Orange O O/B
Green G G
Yellow Y Y
Black X2 E
Blue B C
White W AUX


* - I didn't hook the brown/tan wire up to anything. This wire should be taped or capped so it doesn't touch something else and cause a short.

Finally, if you get a new thermostat, don't just throw your old one in the garbage! The WeatherTron contains a mercury switch and needs to be disposed of properly. Find a place that can properly handle mercury disposal and let them take care of it. A lot of cities and counties have arrangements to take it for free and it's worth the trouble to not let mercury spill into the environment.

6 comments:

  1. Thanks for providing this. One question, why did you not utilize the respective heat pump terminal connections on your new thermostat (since your system is a heat pump), instead of the conventional terminal that I see used in the picture. I just wanted to understand all the reasons before tackling this on my own. Thanks.

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    1. The codes from the old thermostat more closely matched the heat pump codes. I don't know what all the codes or colors mean, so that's the best I could do.

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    2. Does emergency heat work with Honeywell ? We have the exact ugly old trane thermostat and looking to replace. Honeywell is pricey , any other options ? Thanks for your blog post and input you may have.

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    3. Yes, emergency heat works with this setup. There's even an option to use an external thermometer to have it automatically switch, but I never did finish hooking that up. You have make sure to get thermostat that supports dual heat though. I couldn't find one at my local hardware store, so I provided the link to the one I got from Amazon. I did see many other options, but I couldn't say how they work since I only had the Honeywell. Since this was something I figured would be stuck on my wall for many years to come, I figured the price would be worth it.

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  2. My Trane wiring system has a white wire that goes to the W terminal with a jumper to the U terminal. And a black wire that goes to the X2 terminal. Yet in the instructions the white wire goes to the E/AUX terminal and the black wire goes to the X2 or E terminal which is also called the E/AUX terminal. Do both black and white wires go to the E/AUX terminal? I have a Trane XE100 heat pump unit outside. I also have a tan wire which was not connected to anything. My old thermostat is a Trane and my new thermostat is a Honeywell Programmable digital WiFi touchscreen model RTH8580WF. Any help would be most appreciated.

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    Replies
    1. Please consult with a professional regarding your issue. It doesn't look like my scenario matches up with yours and I'd hate to see something bad happen to your system. Best wishes.

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