How can I be sure that Sensi thermostat will work with my HVAC system?

Combined Heating and Cooling Systems

The Sensi Wi-Fi Programmable Thermostat works on most combined heating and cooling systems without a common wire, or “c-wire.”

The Sensi smart thermostat also works on most combined heating and cooling systems without a c-wire, however, will require a c-wire for Apple HomeKit functionality.

The Sensi Touch smart thermostat always requires a c-wire.

Heat-only or Cool-only Systems

On heat-only or cool-only systems, Sensi thermostats require a c-wire. A heat-only or cool-only system without a c-wire installed will cause the Wi-Fi connection to drop out after about two hours of operation. The Sensi Touch smart thermostat requires a common wire for basic operation.

If you need a c-wire, there are a few main options:

• Using an extra, unused wire as a c-wire
• Using your thermostat’s g-wire (fan wire) as a c-wire
• Installing an Add-a-Wire Kit (These kits can be purchased from another manufacturer and used with Sensi.)

If you would like to understand what a c-wire is and learn more about these three options, watch our helpful videos on our c-wire page.

If you have a 2-wire, heat-only system, you could also install a 24VAC power transformer to supply constant power to your Sensi thermostat.

Incompatible system types include:

• Line Voltage Systems (generally 110V/220V baseboard heating)
• Systems with remote sensors - While the Sensi thermostat may be compatible with this system type, it will not be able to gather data from existing remote sensors
• Proprietary or Communicating Systems - The Sensi thermostat can’t communicate with serial protocols, although some proprietary HVAC equipment can be wired with standard HVAC wires
• Stranded wiring – Wiring at the thermostat should be the standard 18 gauge thermostat wiring for best performance.