Thank you so very much! Since there are 2 positive terminals on the i3, I assume it doesn’t really matter which one I use?
Google said Ademco was acquired by Honeywell, so I called them and they suggested this i3 model should work, but their support could only send me the wiring diagram, which didn’t help a newb like me.
I will try it and respond here - might be a little while though. Thanks again!