Unexpected wiring found on existing thermostat


  #1  
Old 03-20-10, 10:21 PM
M
Member
Thread Starter
Join Date: Mar 2010
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Unexpected wiring found on existing thermostat

Hi,

I am replacing my thermostat. The existing wiring: Furnace Wiring.

1. Why is the existing thermostat wired backwards (R --> W and W --> R)?

2. Why is G (fan) controlled by a relay and switch located in the basement rather than the thermostat? Is it for mechanical 2-wire thermostats?

3. Is the new wiring reasonable?
R --> R
W --> W
G --> G
C --> C

Thanks for any help!
Brian



Other details:
Trane XE80 natural gas forced air furnace with White Rodgers 50A65-475 ignition control board
Current thermostat is a LUX 1500
New thermostat is a HAI RC-80
My place is a townhouse condo built 1999 in Calgary, Canada
 
  #2  
Old 03-21-10, 05:42 AM
L
Member
Join Date: Mar 2010
Location: MD
Posts: 106
Upvotes: 0
Received 0 Upvotes on 0 Posts
I am replacing my thermostat. The existing wiring: Furnace Wiring.

1. Why is the existing thermostat wired backwards (R --> W and W --> R)?

They may have gotten the wires crossed,
It would have been a bigger issue if you had Y or cooling connected.


2. Why is G (fan) controlled by a relay and switch located in the basement rather than the thermostat? Is it for mechanical 2-wire thermostats?

I suspect that the way they miswired it they where unable to energize G for the energizing the fan

3. Is the new wiring reasonable?
R --> R
W --> W
G --> G
C --> C

Yes and it will be alot better .
 
  #3  
Old 03-23-10, 10:13 PM
user 10's Avatar
Member
Join Date: Mar 2004
Location: NA
Posts: 1,830
Received 57 Upvotes on 50 Posts
On heat only systems with no fan control it really doesn't matter if R and W are reversed.

When there's a demand for heat, the stat makes an internal connection between R and W. The G terminal isn't necessary unless you wish to switch between continuous and intermittent fan using the t-stat or you're planning on adding a/c. (On/auto)

C is common - if the t-stat isn't battery powered, don't bother connecting it.
 
 

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