What can the Z terminal on the Smart Thermostat be used to control? Follow The Z terminal of the Smart Thermostat can currently control a third heating stage, a humidifier, or a dehumidifier. Facebook Twitter LinkedIn Submit feedback Comments 0 comments Article is closed for comments. Articles in this section What kind of batteries does my Smart Thermostat Use? Smart Thermostat Battery Replacement Guide My Smart Thermostat buttons flash amber and screen does not illuminate What can the Z terminal on the Smart Thermostat be used to control? My system has an external air baffle for fresh air. Can the Smart Thermostat work with my system? Does the Smart Thermostat support systems with multiple zones? Does the Smart Thermostat support multistage systems? Which HVAC systems are compatible with the Smart Thermostat?