Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I took the old thermostat off, and had G,Y,W,Rc and '4' terminals connected to the Green, Yellow, White, Red and Black wires respectively.

Voltage from Rc to G|Y|W was 24VAC as well '4' to G|Y|W was 24VAC

all other combos read less than one volt, so I'll assume that's just noise.

The new Thermostat requires GYW, Rc and Rh (or a wire to Rc and a jumper to Rh)

So, what's the Black wire for? Do I just tape it off and ignore it?

share|improve this question
up vote 7 down vote accepted

I found the manual for the old thermostat on the web.

Turns out '4' is an alternative label for Rh on some old models.

I guess I needed that.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.