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I'll start by saying I'm a complete novice when it comes to HVAC, so anything I'm saying here has been learned from the interwebz in the last 2 days.
We just moved into a new house (new to us - built around 4 years ago) and want to replace our existing Honeywell thermostats with Ecobee4s (already bought).
Upon removing the existing thermostats from the wall, there were only 3 wires (labelled 1, 2 and 3 on the wallplate. Data, R and C on the back of the thermostat itself).
After some googling, it seems that we have EIMs installed on the furnaces in the attic.
We have 2 separate units (upstairs and downstairs, both in the attic).
From what I've read, it would seem that we will need to bypass the EIMs and wire directly from the thermostats to the units. The wires are all there in the wall, so that shouldn't be TOO hard (I think).
The two systems seem to be identical with the exception of a box on the ducting on the one on the left (as you enter the attic), which has wires going into it. I have no idea what this is, whether it complicates things or if it's something we'd lose the functionality of with an Ecobee?)
I have taken pictures of the wiring as best I can and would appreciate if you guys/gals could give me any assistance in getting this working (or just tell me that I need to return the Ecobees or call a pro).