Trane XL80 furnace thermostat wiring questions

Hello all,

I have a Trane XL80, 2 stage furnace and am replacing the old thermostat with a new Honeywell 8580 Wi-Fi Thermostat. I have 4 wires connected to the old thermostat, W, R (jumpered with RC), C, & G. I also have 1 wire that is unused and not connected to anything.

During the setup of the new thermostat, it mentions the importance of configuring your your system if it is anything other than a traditional gas forced air system. It also states that if the furnace is a multistage unit, then the thermostat must be configured accordingly. Seems straightforward. But my old thermostat wasn't capable of operating a 2 stage furnace, but yet my furnace did indeed operate with both stages. So down to the furnace I go to verify the thermostat wires connected to the control board. And what I found has me confused as to how to connect my new thermostat.

At the control board, I have 4 wires connected. R, G, & C, but there are 2 terminals labeled W1 & W2, that is connected to the W wire from the thermostat, with a jumper between the two. Now I'm confused!

The furnace is using both stages to heat, because after about 5 minutes or so, the blower motor will kick into high until the set temperature is reached then shut off. All of this must be controlled by the furnace board, because my old thermostat couldn't operate the two stages function. So my questions with the new thermostat is 1) should I just leave it connected as is and let the control board control the 1 stage/2 stage heating? Or should I remove the jumper between W1 & W2, connect the unused wire to W2 on the control board and W2 on the new thermostat and configure it to control the multistage function of the furnace?

Sorry for the long post, but I'm a little confused as to what the proper way to proceed is. Thanks for the help!

 

Michael, Welcome to the forums.

You are correct in presuming the firing rate was controlled by the board on the furnace. Your new stat is able to control a two stage furnace & should be used to do so. Five minutes to go to high fire is way too fast. Two stage furnaces are most efficient at low fire.

If you don't have the installation manual for your furnace (just to confirm the W1/W2 connections) use your model number, usually on a sticker near the burners, to do a search for it.

I think you can configure that stat for the temperature difference in low & high fire. Most people use 2*. If the room temp is 2* or more below the setting on the stat, it will put the furnace into high fire.

 

Hi Grady. Thank you for the welcome, and the reply.

I have cross referenced the manual and verified this is the proper connections. But one thing I couldn't find mentioned is if I need to do anything else in terms of telling the control board that the single/two stage functionality has been passed to the thermostat. Is there a DIP switch that needs to be adjusted, or will the control board just know because w1 & w2 are no longer jumpered?

Thanks again for the help.

 

http://www.trane.com/content/dam/Tra...3_02012013.pdf

The dip switch settings are in the manual.
Is this your furnace?

 

Hi Houston204. Thank you.

Yes, this is my furnace. Weird, the manual I have (downloaded version) only shows the "Field Wiring" options and mentions (nor shows) nothing about the dip switches?

OK, I see the dip switches, but I'm feeling really stupid because I still can't see what the switches should be set at to allow the thermostat to control the 1st and 2nd stages?

Any help to point me in the right direction would be greatly appreciated.

 

S1-1 = off
S1-2 = off

 

You should also verify that the stat Y is connected to the furnace Y so the blower runs in the correct speed for cooling.

 

Houston,

Thank you for clarifying the DIP switch settings for my situation.

I don't have a cooling system installed, so the "Y" connection is unnecessary, correct? Or should I connect it anyway?

Thanks for all you help.

 

Y would not apply without cooling.

 

Thank you! Got everything wired correctly and now the thermostat is handling the single/two stage transitions. So far I've noticed the furnace not kicking into high gear for short periods of time (30 seconds) before turning off.

Thanks for your help!