I am removing a old (1987) Honeywell Mercury THermostat Q472L Base that has W, R, Y, G, B, O. The RTH230B has Rc (which I assume to be B), Rh (which I assume to be R), Y (to Y), W(to W), G (to G). I have no idea what to do with the O (which I read could be the Changeover.

Do I just tape it up and leave it? I would appreciate any suggestion. Thank you.

Do you have a heat pump system? What kind of heat and a/c system do you have?

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Originally Posted by russellhg13

I am removing a old (1987) Honeywell Mercury THermostat Q472L Base that has W, R, Y, G, B, O. The RTH230B has Rc (which I assume to be B), Rh (which I assume to be R), Y (to Y), W(to W), G (to G). I have no idea what to do with the O (which I read could be the Changeover.

Do I just tape it up and leave it? I would appreciate any suggestion. Thank you.

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I have a heat pump system. When I connect not using the O wire, the heat system works but the AC will not. I can hear the relay cut on but nothing else.

In the meantime, I am back on the old system until I figure this out.