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greg0081
Jun 17, 2009, 01:24 PM
I have the honeywell rth221b thermostat and coming out of the wall i have red white green yellow and a blue they all match the thermostat except for the blue wire not sure ware to put it the thermostat has a rh rc white green and a yellow ports
wmproop
Jun 17, 2009, 07:55 PM
blue is probably common,,used to run the stat instead of needing batteries
isn`t realy needed if you have a battery operated tstat