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joe c 06-09-2008 06:48 PM

thermostat type needed with temp-a-trol MSC-3
Hi everyone.

I updated my thermostat's last fall to Honeywell RTH110B's (home depot)which have heat/off/cool switch and fan auto/on switch (non programable), previously I had the old style mercury dial thermostat's and in my basement I have a honeywell temp-a-trol MSC-3 switch that I can set the fan on or auto and heat/fan/off/cool. In the fall I was able to get the heat to work but now am unable to get the ac to work unless I put the white wire on the Y port, but when I do that it doesn't turn off when it reachs the desired temp set. Each zone has 3 wires, bedroom has red/white/ has red/white/blue. The new digital thermostat
has Rh RC (with jumper) W Y G. I had the red wire on Rh, white on W, and blue (bedroom)/black(kitchen) on G and the heat worked but now when I switched the MSC-3 to cool I get no ac. I'm thinking I need to get different thermostat's that just control temp and not the same functions as the MSC-3 but I'm stuck and not sure. Any help would be greatly appreciated!

Thanks, Joe

PS. its 86 in the house....HELP

geo fan 06-13-2008 06:12 PM

go to the air handler disconnect power open cabenit y is ac g is fan look to see what colors they used and match at t stat if you heat and cool are controlled by different system ie. hot water base board and a seperat ac system you need to look for what coler they used for r and remove the jumper rh heat rc cool 24 v supply

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