Wiring a programable thermostat

[OkieDavid]

I messed up and left my schematic at home but I'm going to try from recall. Old thermostat (central heat/air heat pump) in one of the mercury kind with the following wires- Green wire to terminal "G", Red wire to terminal "R", Yellow wire to terminal "Y", Blue wire to terminal "B", White wire to terminal "W", Orange wire to terminal "O"... Also contains a tan wire, can't recall other color and a disconnected black wire for a total connected wire set of 7.
New programable thermostat (Hunter brand) only contains 5 terminals total (instructions state that if you're using a 4 wire system you leave a jumper in. Terminals are labled in two letter combinations (example: RC, RH, YO). Instructions ask you to locate specific terminals on the old unit and mark the wires attached to them. The problem I had is the old thermostat terminal markings are single letter (see above) and don't match ANY of the two letter terminals on the drawing.
Anyone got experience with this system? I'm assuming one of the terminals on the old thermostat is used to activate the "emergency heat" function which the new thermostat doesn't appear to have. Another terminal on the old thermostat is for the ground circuit which won't be used on the new "self powered) thermostat. Ended up just reinstalling the old one to have AC last night. I can figure out the "cold" circuit and the "fan" circuit but I'm lost on the heat circuit? Confusing I know but I'll check back later to answer any followup questions.
Thanks

[agmantoo]

There is no specific single standard for the wiring a heatpump. Wiring can and will vary from brand to brand. If you make an error you are likely at least to burn the transformer or at worst damage the circuit board. Either call someone at home and get them to read to you your notes or let it go until another time.

[cfabe]

If your new thermostat doesn't have the emergency heat terminal I think it's probably not the right type of thermostat for a heat pump system.

[tyusclan]

Thermostats come with the schematics and info for the varying brands of heat pumps. Definitely get that before you try to wire it. The chances of you doing it blind and getting it correct are very slim.

[Ross]

I'm not going to second guess the installer either. You can only hope he/she followed the common colour coding. I will give you this site.
http://www.toad.net/~jsmeenen/wiring.html

[pred]

The new therm will handle 2 transformers....
Jumper can be used btwn RC and RH,
RC= red cool
RH= red heat
Your old therm did not acept 2 transformers, So you will need a jumper btwn RC+RH
The other colors should match up.
The Blue is to reverse the refridgerant flow for heat pump.
Red is HOT
Yellow turns on AC outside
white is back up heat (Not Heat pump)
Green is fan.
Hope this makes sense to you and may the force be with you!
Peter

[OkieDavid]

Thanks for the help guys. Cfab- I was able to determine that I had in fact purchased the wrong thermostat for a heat pump system so I just wired the old one back in.
I called the original installer to see what brand he recommended as the thermos for a heat pump system are quite a bit more expensive ($90.00 vs $25). After looking at the schematic for a heat pump installation I'll have to break out the multi meter since it's not as simple as red-red, blue-blue etc..
Thanks again,
David

[Ross]

Can you not just track back from the appliance to determine which wire is controling what?

[OkieDavid]

Yes Ross, that's what I will have to do once I aquire the correct thermostat. Hence "break out the multi meter". I'll have to locate the defrost circuit and freon reversing valve and see which "color" is controlling that circuit. The remaining circuits are pretty straight forward. Pulled up the install schematic on the installer's "preferred model" and saw that there are about 5 different configurations depending on what brand heat pump you are using.