Thermostat C wire connection on Trane

Reply

  #1  
Old 03-09-19, 02:14 PM
Member
Thread Starter
Join Date: Mar 2019
Location: United States
Posts: 7
Received 0 Votes on 0 Posts
Thermostat C wire connection on Trane

I purchased a Honeywell RTH6500 Wifi Thermostat, which requires a C wire. My old thermostat showed a connected blue wire to its C terminal. However, it was battery-powered. If I removed the battery, the thermostat screen would go dark. This is pretty close model of my old thermostat:
https://pro.luxproducts.com/wp-conte...NG_Manual1.pdf.
Below is a picture of my old thermostat wiring.



After I connected the RTH6500, I measured with a multimeter, which showed 0V on the C terminal. All the other connected terminals showed positive voltage. I went up to the air handler and saw there was a unconnected blue wire.



I'm guessing the three sets of wires are going to the (1) air handler, (2) heat pump, and (3) thermostat. You can see the green wire is also unconnected on a different set (branch). The green wire on the thermostat is connected to G terminal, which I think is the fan. I think that set of wires is probably going to the heat pump, since it doesn't have a fan?

After getting some help from another forum, I opened up the air handler, expecting to see a C terminal for common, but I only see the blue wire connected to a B terminal. I looked at the new Honeywell thermostat's wiring diagram, and it shows B can also go into its C terminal. I'm 90% ready to go ahead and strip the unconnected blue wire and add it to the wire nut connecting the other two blue wires. I just want to get some opinions before I do it.



FYI, I have two air handlers and two heat pumps. The air handlers are Trane TWE030C140F1 and Trane TWE 042C14FB1. The heat pumps are Trane TWR042C100B2 and Trane TWR030C100A4

Thanks for any guidance you can provide.
 
Sponsored Links
  #2  
Old 03-09-19, 02:55 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,219
Received 477 Votes on 447 Posts
Welcome to the forums.

On a Trane unit..... the B is the same as C. Connect all three blue wires together in that splice.
 
  #3  
Old 03-09-19, 07:17 PM
Member
Thread Starter
Join Date: Mar 2019
Location: United States
Posts: 7
Received 0 Votes on 0 Posts
Thanks PJmax. I did that and my new thermostat now has power.

I'm now trying to program my thermostat, and I originally set it to "Heat pump WITHOUT backup or auxiliary heat" because none of the W1/W2/W3 terminals at the air handler were connected. However, I just read this thread, https://www.doityourself.com/forum/t...tween-y-w.html. The original poster and I both had Y jumpered to W on our old thermostat, and the recommendation there was to select heat pump WITH backup or auxiliary heat, so now I'm not sure anymore.

Can anymore provide guidance here?

Thank you
 
  #4  
Old 03-09-19, 08:46 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,219
Received 477 Votes on 447 Posts
There is no jumper required and you do not have back up heat. You must be in a warmer climate where only minimal heat is needed.

Red ----> R/Rc
Blue ----> C
Green ----> G
White -----> O/B and programmed for O to cool.
Yellow ----> Y
 
  #5  
Old 03-10-19, 11:09 AM
Member
Thread Starter
Join Date: Mar 2019
Location: United States
Posts: 7
Received 0 Votes on 0 Posts
Yes, I live in Phoenix, Arizona. So, following your advice, I will set my thermostat to the function in the green box and not in the red box.



Can you please me your blessing? Thank you.
 
  #6  
Old 03-10-19, 12:13 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,219
Received 477 Votes on 447 Posts
Yes.....use choice #1 in the green box. Consider yourself blessed. Name:  smiley-thumb - S.gif
Views: 524
Size:  1.3 KB
 
  #7  
Old 03-10-19, 01:48 PM
Member
Thread Starter
Join Date: Mar 2019
Location: United States
Posts: 7
Received 0 Votes on 0 Posts
PJmax, thank you so much for your kindness and patience.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: