Is the air immediately behind the humidifier panel more humid than the air 5ft away from it?
I'm planning on running a wire from the C furnace panel to the humidifier then the acc+ from ecobee
Did you jump C and acc - behind the thermostat or do you have a powered fan humidifier?
I'm guessing your Ecobee question might be directed at me? I have an Aprilaire 760, so it's a powered fan model. It's plugged into an outlet in the furnace room. I don't remember the details exactly, I just followed the included directions for a two wire install. We had an existing humidistat mounted near the thermostat already, so I just moved the wires over to the Ecobee.
The internet is full of debate over supply vs. return side. Sorta like Pennzoil vs Valvoline. I'm no pro, so won't jump in the argument. I'm pretty sure my humidifier would be more efficient on the return side - just because of the negative pressure differential, vs fighting the positive pressure on the supply side. And I don't think the air going into the heat exchanger would be moist enough to make any difference. It's a small amount of air blown through a pad, which is then mixed with a lot of incoming dry air. Just my 2 cents based on internet reading.
I'm excited to try to humidity programming on the Ecobee that varies humidity based on outside temp. That's something I've forgotten to do before when the temp dropped, and had the iced up windows to prove it. But overall, I really like the whole house humidifier. Hope you do too!