Howdy,
Thought Id try this out. I have a Duo-therm six wire thermostat that I am replacing due to the very common circuit board problem with these models. I have purchased a Honeywell RTH2300 digital with heat pump connections. I don't have a heat pump, I didn't realize that it had this when I bought it, got it on a whim. I am now trying to connect the Honeywell RTH2300 to the existing Duo-therm and need to know what to do with the black- GND wire? Can't I just ground it anywhere? Does this Honeywell have a spot on them where I can ground them? Why doesn't Honeywell include in the installation method what the letters are for, for instance, what is the G, is it ground or green, because some greens are fans some fans are blue wire but the B is for heat pump... etc. I have it pretty much figured out cept for the ground and the two fan speeds. This is what I know:

Duo-Therm: Honeywell:
Red = +7.5 O/B = ? Im guessing Heat Pump
Yellow = Cool Y = ? Im guessing Cool
White = Furnace R = ? Im guessing Power, +7.5
Blue = High Fan G = ? Im guessing Ground, but thinking fan, while I have my black GND connected
Orange = Fan to it.
Black = Ground W = ? Im guessing Furnace

As you can imagine, I have the Y and the yellow wire connected properly, as well as the W is furnace. I have the +7.5 red wire connected to the R on the Honeywell. I then have the Black or GND connected to the G terminal on the Honeywell. I do not currently have the blue or orange wires connected as for I do not know where to put them. I believe they go to the G terminal except only one of them can be connected which means I need to choose if I want hi fan or fan. Unless I can use the O/B terminal for the fan operations? If not, I can live with one fan speed. So, I need to know if I can ground this black GND wire to the honeywell, if not, can I just ground it any ol place? Then the fans, am I correct in assuming that I will only have one fan speed? If so, then I think I need to put the Orange Fan wire to the G terminal, which means I would have to remove my current setting of the black one in the G terminal and then that would stop the functioning of my furnace which would leave me in the cold, literally. Oh, why is the unit half way working with the black hooked to the G terminal if the G terminal is fan because my black is my ground wire, I don't get it? I mean obviously its grounding but not frying anything? Hrm. I hope some one can help me with my "situation". Thanks in advanced!

Mike WhoRu??

This is not an answer, is there a way to edit my question? This is how the chart should read in my question above:

Duo-Therm:------------------------- Honeywell:
Red = +7.5 ------------------------R = ? Im guessing Power
Yellow = Cool ---------------------Y = ? Im guessing Cool
Black = Ground ----------------O/B = ? Im guessing Heat Pump
Blue = High Fan ----------------G = ? Im guessing Ground, but thinking fan, while I have my black GND connected
Orange = Fan --------------------to it.
White = Furnace -----------------W = ? Im guessing Furnace

o.k,not a pro,but first things first.. I assume its an r.v. tstat you are replacing.so,the honeywell,is it battery powered?it has to be to do the modification you want,if it isn't,go get a tstat that is.now,the wire marked +7.5,disconnect from old duo therm and cap it or tape it,you will not need it.Any connection points on the new stat related to heat pump are not needed either.now make a choice,do you want hi or low fan operation,if you want both,you will have to hard wire your own switch to make that happen,and that's a whole other animal,so I would just go with the low speed,its usually enuf and quite.so you can just tape or cap off the hi fan wire on the old stat... now look at what's left,things just got a whole lot easier.so lets see,you have heat wire,cool wire,fan wire,and a ground... now just go to instructions for new stat,mine isn't a honeywell,but most are similar... G is fan relay,R is ground,Y is cool,and W is heat... just look at instructions and diagram that came with you new tstat to see what your letters are and what they stand for,hope this helps,and remember,don't overcomplicate it by worrying about all the colors and letters,just lable the old wires what they are before you unhook them,and match to new tstat... BE SURE TO DISCONNCT R.V. FROM SHORE POWER AND DISCONNECT BATTERY BEFORE YOU DO THIS TO AVOID FRYING SOMETHING,NAMELY THE MOTHERBOARD IN YOUR Furnace OR A/C,VERY PRICEY FIX THEN... good luck

Thank you Good Sir. My problem was with G. I thought it was the ground so I connected my ground to it. Then I thought R was power because red is usually. Man was I ever turned around. To answer your question above, yes, it is battery powered. Thanks again. My new digi thermometer is working splendidly. Good day!

Thank you so much for your most valuable and useful information! I was informed by a local RV dealer that the parts alone to replace my analog Dometic thermostat would cost about $120 plus installation. With your information I was able to install a Honeywell thermostat for the price of less than $20 and it works fine. I can do without the "hi" fan setting. Thanks again!