Hello,

I am looking to get an Ecobee3 thermostat, but I looked at my wires to my existing one and was a bit confused as one is just marked as data. I saw a post saying it was best to get a listing of all the equipment I have so I that is below. I am not sure if I would need a new EIM or would need to chance some wiring. I know very little about HVAC systems, but the EIM's wires are easy enough to add so changing them around wouldn't be hard if needed. Wasn't sure if only having 3 wires would limit the Ecobee3's functionality at all. Attached is a picture of the wiring into my EIM and just the top left wires for 1, 2, and 3 go to the existing thermostat. I do have 2 wires that are run in that bundle that are not in use so I have them available if 2 more wires would be helpful. Very grateful for feedback on this.

Here is the equipment that I have:
Lennox 14HPX-024-230-18 - Outside unit
Lennox CX34-25A-6F-1 - Heat pump/ air handler (inside)
Lennox EL195UH045XE36B-02 - Gas Furance
Honeywell THM5421C - Equipment Interface Module

 

You will need to lose the EIM.

 

Do I need to get a different one or just connect the wires manually and run some up to the thermostat? A bit unsure on if I ditch it entirely what would need to be run to the thermostat and what just needs to be connected together in the basement.

 

You need 6 orange wire nuts and at least 6 conductors in the wire bundle to the thermostat.

Connect thermostat blue to the two blue wire that were on C.
Connect stat red to the 2red wires on the R terminals.
Connect stat orange to the 2 wires that were on O/B.
Connect stat white to the 2wires that we're not Aux1
Connect stat yellow to the yellow wire that was on Y1.
Connect stat green to the green wire that was on G.

At the thermostat...
Red is RC
Green is G
Blue is C
Yellow is Y1
White is W1(Aux1)
Orange is O/B.

Reversing valve is energized to cool.

Omit the 2outdoor sensor wires black and brown.