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Do I connect old, unmarked thermostat wires to new thermostat?

Asked Nov 4, 2011, 07:00 PM — 2 Answers
Hi folks, I have an old mercury Honeywell thermostat with two unmarked wires sticking out of the wall. They almost look like thin audio cables, with one lighter in color than the other. I was planning on replacing it with a new Thermostat for the forced hot air gas furnace (which is probably about 10-20 years old now). Would it damage either unit if I connect the wrong wires (i.e. switched) to the W and RH connectors on the new thermostat? Sorry if this sounds stupid. I'm obviously a noob.

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mygirlsdad77's Avatar
mygirlsdad77 Posts: 5,539, Reputation: 1650
Plumbing Expert
  
#2

Nov 4, 2011, 07:45 PM
With your setup, just hook one wire to r and one to w and you will be fine. Doesnt matter which goes where. Hook er up, and you will be in heat. Take care, and please let us know how things work out.
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ipbrjt3's Avatar
ipbrjt3 Posts: 3, Reputation: 10
Junior Member
  
#3

Nov 4, 2011, 09:50 PM
Things worked beautifully! I also did some further research and read that this configuration is just an "interruption" in one line- so it doesn't really matter which is RH and W. Thanks for confirming it for me!
:-)
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