Configuring the ACC+/- Terminals on Ecobee as Dry Contacts to energize AprilAire Steam Humidifier

Welcome to my channel! In today’s video, I walk you through how I wired my Ecobee Thermostat’s ACC+ and ACC- terminals to function as a dry contact signal for my AprilAire Model 800 Steam Humidifier. This setup allows the Ecobee to seamlessly control humidification calls without sending a continuous 24V signal—perfect for systems that require a “dry” switch to engage the humidifier.

I start by showing you the wiring connections at the Ecobee Thermostat, focusing on the ACC+ and ACC- terminals, and then move to the carrier board inside the Carrier Crossover Air Handler (Model 40MUAAQ24XA3) to illustrate which terminals are engaged. Because this system is using Scenario #1—the standard 24V thermostat control to manage the overall system—I also demonstrate the dip switch setting that must be changed at the indoor unit for it to function as a “communicating” system when paired with the Carrier Crossover Heat Pump (Model 38MURAQ24AB3).

One of the unique features of this Carrier Crossover system is how the indoor and outdoor units communicate using only a two-wire (16-gauge stranded) connection. Despite having just two leads running between the units, they still exchange information needed for optimal performance. You’ll see the exact location on the air handler control board for these wires and how everything is integrated with the Ecobee’s humidifier control terminals.

By the end of this tutorial, you’ll have a clear understanding of:

1) How to wire the Ecobee Thermostat’s ACC+ and ACC- for a dry contact signal

2) Which terminals on the Carrier Crossover Air Handler board to use

3) How the Carrier system communicates with only two leads

4) Which dip switch to change for Scenario #1 with a 24V thermostat (I.e., Ecobee) #hvac #hvactechniques #copperwork #efficiency #hvactools

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Thanks for watching, and feel free to leave any questions in the comments section below!