Can Mysa Smart Thermostat control a heat pump with a humidifier wire?

Last updated: August 17, 2026

Overview

Mysa Smart Thermostat can be compatible with many low-voltage heat pump systems, but the current thermostat does not provide a dedicated humidifier accessory terminal.

If the existing thermostat wiring includes a humidifier wire, often labeled H, Mysa cannot control that humidifier connection. The heating and cooling equipment may still be compatible if the rest of the system wiring matches a supported Mysa Smart Thermostat configuration.

What this means during installation

  • Do not connect the humidifier wire to an unsupported terminal.

  • The heat pump can still be reviewed for compatibility using the standard Mysa Smart Thermostat wiring requirements.

  • Temperature sensor wires, such as T/T wires on some systems, are separate from humidifier control and should not be treated as an H accessory connection.

  • If the customer needs Mysa to control the humidifier directly, the current Mysa Smart Thermostat is not the right fit for that accessory control requirement.

What to ask the customer for

  1. A clear photo of the current thermostat wiring.

  2. The heating/cooling equipment type, including whether it is a heat pump.

  3. Confirmation of any accessory wires, such as H, HUM, or dehumidifier terminals.

  4. A photo of the HVAC control board if the thermostat wiring is unclear.

If the wiring includes a humidifier accessory wire, let the customer know Mysa can review the main HVAC compatibility, but it cannot control that humidifier accessory wire.