I am looking to change my thermostat to a digital one. Propblem is, I don't know what to get. I don't know to get one for a heat pump, or central heat and air, If they both heat and cool with indoor and outdoor units, how do you know what I have? I have seen some thermostats for 2 stage systems, what is that? What I have is a Trane, there is an outdoor unit, and an indoor unit. The thermostat is mechanical and when its on heat there is two lights, if its cold enough out the blue "aux heat" light comes on, then there is a red "emergency heat" light. Does that mean it's a 2 stage heat system? I have seen a lot of digital thermostats on eBay, but some say they won't work for heat pumps, and some are for 2 stage, I just don't know what to get. Any help would be greatly appreciated.

You have a heat pump. That "aux" light is telling you it's too cold for the H/P to operate efficiently, so it bypasses it and gives you heat from the furnace only.

Beyond making sure to get one for a heat pump system, the rest of the decision is on features and price.

My experience: The most expensive ones are packed with features that most people would never use.

First you must be commended to be asking the question BEFORE you go and buy the wrong thermostat, and then try to figure out how to wire the unit, all while not having heat. Look at all the previous posts here about needing help to connect a thermostat, and it is getting cold in the house, and you will see what I mean.

The following links are some general help regarding thermostats, the third as a sample of how complicated the wiring can be, esp. for heat pumps:

http://toad.net/~jsmeenen/tranewire.html

http://toad.net/~jsmeenen/wiring.html

http://www.columbustemp.com/pdf/products/honeywell/T7350_datasheet.pdf

Sure sounds as if you have a heat pump, with two auxiliary stages of heat, this being referred to as 'Multi-stage".

And as you already know, there are many thermostats to choose from. Now I am a proponent of hiring professionals to consult and do work that a homeowner is not able to do on his own. Should you decide to tackle this job yourself, there is some prep work you must do.

First, you really need to understand exactly what type of system you have, for several reasons. One is obvious, know how your system is working, what is working when. Once you know what and how your system works, then you will know when it is not working properly to be able to take advantage of it's proper operation for your comfort, and perhaps realize some energy savings, along with the proper maintenance of the system.

You need to get as much information off your system, along with the model number of your exisitng thermostat, and both the indoor and outdoor units, along with any wiring diagrams that should be in the units.

You mention Trane, here is the link to Trane Residential systems (http://www.trane.com/residential/traneowners/traneowners.aspx), that includes the topics of operation and maintenance that I mention, along with manuals for many of their systems.

Look through this information to learn as much as you can, perhaps you may be able to determine the exact thermostat you need to install and wire. If not, then get back with the details of your equipment and we can go from there.

Ok, I am retarded, I walked outside and looked at my outdoor unit and it says heat pump right on it. LOL. It is a Trane XE 800 High effinciency Weathertron heat pump. I have attached some pics of the outdoor unit, and the thermostat, one with the cover on and one uncovered showing the wire set up. Most of the digital thermostats I see mention a four wire set up, mine has 8. I am not a complete idiot, I used to do electrical work, so I can do wiring, I just never messed with AC units. I am wondering If I find a digital thermostat that works with my system, will it just be a wire swap the matching terminals, or will I have to figure out what wire is what to put it in the correct terminal for the new stat? If someone can point me in an inexpensive direction of the type of digital stat I need, that would be great!! Thanks

I need to suggest that you contact Trane, have the model numbers of the heat pump and the thermostat ready, so that they can suggest the correct thermostat for your system.

You can find a dealer at this link:
http://www.trane.com/Residential/DealerInfo/DealerInfo.aspx

I believe you need their tstat # TCONT802, but since you have not provided and model numbers, and the Series XE 800 number is not acknowledged at Trane, it is probably an older system, no longer sold and supported.

Trane does not provide any of the wiring diagrams for their equipment on their web site. If you open your unit you should be able to find the units wiring diagram. You need to review this to determine the purpose of each wire between the unit and the thermostat.

You will definitely need an 8 wire thermostat, however, you cannot choose one only based on the quantity of wires, as each stat is designed for the specific unit, since you seem to have a three stage heat, and 1 stage cooling, this is not a plain vanilla unit.