[KISS]

Are you at all interested in fixing this the BEST way?

I'd like to try to scrap the TAY103A and use a better, although more complicated thermostat to set up, but you have to run two wires to an outdoor sensor someplace. My favorite spot is under a telco NID. Shady and free air. Is that difficult for your to do? Or want to do?

Take a look here which backs me up: Is fossil fuel kit needed with Honeywell VP IAQ stat? - Heating & Air Conditioning Forum - GardenWeb


The 8320 or the 8321 (dehumidification) would work nicely. honeywell dual fuel - iaqsource.com

See the install guides.

I liked the pics. You could have moved the wires out of the way so one could see the terminals.

With this setup, you can choose if you want to use a HP and when the gas furnace is used. By using emergency heat, you can force the system to use gas.

You'll need an outdoor sensor.

Meanwhile back to the current problem.

Can you go outside and take some pictures. Remember to disconenct the outside unit. There should be a schematic there on the removed door or somewhere. There should also be a circuit board domewhere. Take a pic of this. Also find the model # on the outside unit and look for any documentation that should have been left with the homeowner.

OK, so far.

What I'm really worried about in your current setup, is what the temperature is when the heat pump is turned off.

I found the TAYPLUS wiring diagram here: http://hvac.amickracing.com/Heat%20P...Tayplus103.pdf

X2 is really E; a TRANE exclusive and B is really C (Common).
"T" is probably used to measure outside temperature and can be discarded. It looks as if the ODT locks out the gas furnace at it's setpoint. If you wanted to operate the system better you would need a stat that utilizes the "T" terminal. That would be a thermister that would measure outdoor temperature and lock out the heat pump.

If I'm reading this correctly, it does appear that a dual fuel stat would be a better option. Since this is living space, dehumidification would be a good option.

So, you have a wiring diagram: 2H/1C with emg/aux heat. Heat pump. The heat pump will act stupid at low outside temperatures.

Make sense? B is not the complement of O in a trane system. X2 is E. Fun, isn't it?

I'm still suggesting the 8321 VP stat with an outdoor sensor. eBay sometimes is a good source for the stat.

[KISS]

I have now wired the Honeywell as follows:
Black - E
Blue - C
Green - G
Yellow - Y
Orange - O/B
Red - R (jumpered to RC)
Brown - Taped Off
White - Aux

I generally like those connections EXCEPT, you probably need a jumper from E to AUX.

Also brown doesn't match your original data of joined.

[KISS]

Your questions:

I don't know if you missed this part of my story, but I am able to heat my home now with the thermostat wiring I gave in my first post. The trick to getting it to use the gas furnace and not the heat pump is to set the thermostat to Emergency Heat. That has worked for me today.

I don't think I want to going doing temporary rewiring in the state I have described.

What I'm now trying to figure out is:
1. Why is my heat pump trying to heat my house (if I don't have emergency heat enabled) when it is 25º outside?
2. Is my TAYPLUS unit supposed to stop it from doing that?
3a. I'm under that understanding that it is never okay to run the heat pump and the gas furnace at the same time. Is this true?
3b. What can I do to fix it? Is this something that the thermostat should correct, aor the TAYPLUS unit?
(now that KeepItSimpleStupid raises the questions)
4. Do I have a multistage furnace?
5. Do I have a multistage heatpump?

You probably need to jump E to Aux. Putting it in emg heat causes the furnace to provide heat.

Now your questions:
1. The tstat doesn't know the outside temp. Some Honeywell Visionpro tstats have dual fuel versions. Some also have dehumidification. In order to use that stat, you need to run two wires to a sensor outside. Good spot, under a telephone NID. Using a propreitary thermostat that used the "t" terminal. It would accomplish that too. See the TAYPLUS manual.
2. No. The Tayplus unit prevents the HP and gas Furnace to be on at the same time. It CAN be jumpered to lockout the gas furnace ABOVE a certain temperature.

3a - true

3b - that's the job of the TAYPLUS unit or a duel fuel thermostat with an outdoor sensor which CAN replace the TAYPLUS unit

4. No. You only have a W terminal

5. Not likely. You would need Y,Y1 or Y1,Y2 terminals

Conclusion:

Jump E to Aux

In order to fix the heatpump running at 25 deg outside, you need a dual fuel tstat with an outdoor sensor. 2 or 3 Honeywell VP models will work. One model, I think uses 3 or 4 wires.

Setting system to E heat will make it use the gas furnace,

The TAYPLUS unit can stay (be redundant) or be replaced with a dual-fuel stat and sensor.