I'm trying to install Ecobee, and like many others, I do not have C wire at the thermostat, thus need to find it on my air handler. My air handler is from Allstyle and the model number is HFD36-42840G-10KW (with heating). Below are pictures of the original wiring diagram on the unit and the newer wiring diagram on the company's website. Comparing the two, they are exactly the same. The only difference is the Thermostat connection part. (???)
On the original one, the "purple" wire is the Y wire, it will go to the outdoor compressor and come back to the thermostat, which seems reasonable, as Y wire controls cooling (right?). This match my current connection, the wires are connect to W G R Y on my current thermostat.
But on their new website version, the diagram connects the "purple" wire to "C" on Thermostat without any mention of cooling. (???so that the air handler works as standalone heater and air blower?)
So, in my case, is both Y wire and C wire the same wire (the purple wire) in my case? Is it right/ok for me add one extra wire to connect the 'purple' wire to Ecobee C wire socket?