Installing ECOBEE 3lite with dual fuel and possible issue

[Sw0226]

Hello, I want to upgrade my thermostat to an ecobee 3lite I picked up, but, have a few concerns.  My current set up is dual with heat pump, and propane.  On the heat pump is a temperature sensor with dial switch that I guess it uses to determine whether to use propane or heat pump based on the outside temperature.  For the most part it seems to work, I adjusted it down  a little so it wouldn't use propane so much, but as far as I know, I cannot choose at the inside thermostat whether it uses propane or heat pump, AND, some times when it is a little colder outside, but hot inside from cooking or something and we turn the ac, it actually turns the furnace on running heat nonstop instead of cool..   I think this is because of how it's wired to work for dual fuel... 

So how would I change my setup when installing the ecobee to make it work correctly for dual fuel?  Would I completely go around/remove the out side sensor and change the wiring around?

I mapped out the current wiring the best I could as changes colors some mid wire and attached my diagram.  I also tried to post pics in order from thermostat, to furnace, to heat pump.

Any help would be greatly appreciated!  Would love to get this working correctly!

[rmuntz]

It's taken a bit to sort through that diagram, but I probably would have wired it differently. Its been a few years since I've installed a heat pump, but W2 should really be your fossil fuel, stage 2, the OD stat should only lock out the HP. They're using the switch as a changeover switch.
The OD stat should be set somewhere around 28'F, that's where the heat pump can't get enough heat out of the air to match the homes heat loss.
Now for the EcoBee, I would need more of a wiring diagram to steer you correctly. The diagram that I pulled up from the installation manual really doesn't give enough info. Truth is, if you wire it the same but lower the OD stat temp you should be ok. I really don't think the Ecobee is going to give you the capability to adjust the OD temp at the stat.