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tlb813 08-12-2012 10:17 PM

need help upgrading manual merc stat to new digital stat
hi to all, new here and need help upgrading old mercury stat to a new digital stat,,hate to start a new subject but i can`t find a wiring situation like mine. here is how my old merc stat is wired

red wire to r
green wire to g
orange wire to o
blue wire to x
nothing at e
nothing at b
white wire is stripped a little and looped around w1 screw and then ends at w2 screw
yellow wire is stripped a little and looped around y screw and ends at L screw
these last two have me confused as the new digitals don`t have a way of looping and continuing a wire I know i need jumpers but i`m not sure where. the new digital stat is a honeywell model RTH3100C it`s wire locations are such and nothing like what I have on the old stat

I`m not sure if I am even using the right digital stat,,and what good is 2 stage heating if the wire is the same white wire w1 and w2 just looped and why does the yellow wire go to y and then loop to L ,,

my house is in florida so need for emergency heat which explains why e is blank, house about 50 yrs old. was an old furnace in closet but was removed by previous owner, has heat pump out back and air handler in attic. system runs fine and always has on old merc stat but it`s sloppy and upgrading will surely help my electric bill out, I have done a good bit of this stuff, I have been a maint. engineer for about 20 years and can build a whole house from ground up, plumb it, lay the elect, etc, hvac certified, pool licensed, and licensed carpenter, but this thermostat has me whipped, I`ve done so much of this stuff trouble shooting a/c units- relays and appliances etc,, i`m gonna go hang my head down and kick the dirt now while I wait for help lol

scottmcd9999 08-13-2012 10:34 AM

You're dealing with a heat pump. The Honeywell instructions should be fairly clear ...

White wire should go to Aux with a jumper to the E terminal.
Yellow wire to Y, and no where else
Everything else color coded

Is your system capable of more than 2 stages of heat? Most heat pumps have only 2 (the "heat pump" stage, and the "auxilliary" stage). Some, however, might have multiple stages, like banked electric strips, or modulating gas furnace.

Also, some contractors would wire the system so that the strips would come on with the first stage of heating. This would significantly reduce the "My heat pump is blowing cold air" calls, but will also ratchet up your power bill. We found a lot of this with lower tier systems (like Goodman heat pumps, for example). Removing the jumper would reduce the electric load, but the customer would sometimes call back in with a "not heating good" complaint.

Aux = Auxillary heat, which is your second stage of heating. The stat will bring it on when needed. E = Emergency Heat, which you would only use if there's trouble with the heat pump. Emergency heat locks out the outdoor unit and runs your heating on electric strips only.

tlb813 08-13-2012 11:59 AM

thanks for the reply
the honeywell instructions were`nt very good it said if you have w1 w2 and y connections then stop and call a contractor,,i`m just afraid of burning out the transformer if i jumpered it wrong, and yes It`s a heat pump it`s a amana model number ASH130241AD and the inside parts are goodman CAUF3030B6AA the only info I can find on it is that it says a split system ,,I cannot even find this model number on the amana website,,and your explanation of the white and yellow wire makes sense and helps me. now i just have to figure out the blue wire on my oldstat that went to x,, on the new stat there is no x to connect to and there was nothing connected to b on my old stat it was empty even though the new stat has a b connection

scottmcd9999 08-13-2012 12:31 PM

Blue wire is often Common from the transformer. Some newer stats don't need it (if they're battery powered vs 24v powered). Try installing without the blue wire to see if it resolves things.

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