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View Full Version : Replacing old standard thermo w/new digital programmable thermostat


babygirl627627
Dec 12, 2009, 07:59 PM
I am removing an old stndard thermostat and replacing it with a honeywell programmable (RTH221B) thermostat. There are 4 wires red, blue, green, and yellow-There is a hook up for Y=, G=, Rh=, Rc=, W= can someone tell me what goes to what. I have tried and only the fan comes on... Pleeeaaassee help help help... thank you

wmproop
Dec 12, 2009, 09:30 PM
On the old tstat,, what tag did each color wire go to?you should have written down what each color wire went to,, if you didn`t you will need to go down to the furnace end and see what each color is hooked to

It should be red wire to rh with a jumper from rh to rc
Green wire to g post
Yellow wire to y post
White wire to w post ( but this is maybe what someone used the blue wire )

Be sure to kill the power to furnace (breaker ) before attempting change

Good luck and get back with us if needed