Replacing old thermostat


Old 10-12-09, 12:40 PM
Thread Starter
Join Date: Oct 2009
Location: Vermont
Posts: 1
Received 0 Votes on 0 Posts
Replacing old thermostat

I am replacing an old Mears thermostat (from the early 70's) in my townhouse. When taking the old unit apart i found that none of the wires were labeled. i have a total of 6 wires. 4 large wires in the center (2 white, 2 black) and 2 small wires on the top of the unit (one red, one white) how do i tell what these wires are and where they should go in the new unit? The new electrical unit i bought has the following slots. RH, RC, Y, W, G and then O, B. i've done a lot of reading about what the letters mean but how do i determine which letters i actually have????

Any help would be greatly appreciated.
Sponsored Links
Old 10-12-09, 04:24 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Received 0 Votes on 0 Posts
Odd that you have different size wire. My guess is the red and white are for heat only (2-wires only, in the sheath). And the other 4 smaller wires are from inside another sheathed wire that they ran at a later date, for perhaps a retrofitted a/c-handler-fan on/auto system.

Never mess with disconnecting wires blindly without knowing what transfers to what based on your original set up. What did the original set up have that deviates from the new set up to confuse you?

If it's beyond any ones guess here, Jay11J, a moderator in the gas heating and thermostat controls forums down below, likes these sorts of questions, it seems. Post there. Or a mod here, can transfer your post there, maybe. ?
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:
Your question will be posted in: