Note: this post has nothing to do with the dreaded "C-wire" that is required to run an ecobee. If you're looking for that, go elsewhere.
One of the more frustrating items for a heating/cooling system is the
sheer number of possible ways to set it up. Sure, there are "standard"
ways, but there are also always other ways.
My previous post on a missing G (fan) wire was not my only issue; in fact, it wasn't even the hardest issue. The actual problem I had - the one I called ecobee about - was that my humidifier wasn't working.
For anyone who may not know, a whole-home furnace-mounteded humidifier is de rigueur in Canada and the northern parts of the USA. The cheapest and most common kind is the "evaporative" kind which uses hot furnace air to work - hence, it only runs when the furnace runs.
There are undoubtedly many ways to wire such a system, most of which the ecobee3 will support. But it sure helps to know what the ecobee3 does.
ecobee3 supports two types: a "one-wire" accessory, and a "two-wire" accessory. According to ecobee support, the thermostat works thusly:
- In "one wire" mode, the thermostat supplies +24V to ACC+.
- In "two wire" mode, the thermostat presents a dry contact across ACC+ and ACC-.
If you put this information together with how your system is currently wired, I bet you can figure out of how to wire and configure the ecobee to run your humidifier (or other accessory).
If, on the other hand, you don't know what a "dry contact" is, this job is likely not for you. Best get a pro to help.