Will Sensi thermostats work with my HVAC system?
Sensi thermostats work with most combined heating and cooling systems, however, the need for a common wire or “c-wire” is different based on the Sensi thermostat model. Please see the chart below for full compatibility information.
| System Type | Sensi Lite smart thermostat | Sensi smart thermostat | Sensi Touch smart thermostat | Sensi Touch 2 smart thermostat |
|---|---|---|---|---|
 |  |  |  | |
| Conventional Heating and Cooling - Gas/Oil/Propane Furnace - Air Conditioner - Electric Furnace - Boiler/Radiant | Yes1 | Yes2 | Yes3 | Yes3 |
| Heat Only - Gas/Oil/Propane Furnace - Electric Furnace - Boiler/Radiant | Yes3 | Yes3 | Yes3 | Yes3 |
| Cool Only - Air Conditioner | Yes3 | Yes3 | Yes3 | |
| Heat Pump/Geothermal | Yes1,3 | Yes3 | Yes3 | Yes3 |
| Whole Home Humidifiers / Dehumidifiers | Yes | Yes | ||
| Communicating/Proprietary System | No | No | No | No |
| Line Voltage | No | No | No | No |
| Millivolt | No | No | No | No |
| RV/Camper 12VDC Applications | No | No | No | No |
1 Compatible with multi-stage systems up to 1H/2C or 2H/1C
2 Common wire required for HomeKit compatibility
3 Common wire required
Combined Heating and Cooling Systems
The Sensi Lite and Sensi smart thermostat work on most conventional heating and cooling systems without a common wire, or “c-wire.” Heat pump systems do require a c-wire.
The Sensi Touch and Sensi Touch 2 smart thermostats always require 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 and Touch 2 smart thermostats require 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) - Sensi is only compatible with low voltage. Consult an HVAC professional regarding step down transformers.
- 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.
- 12VDC (RV/campers) - Sensi requires 20-30VAC. You can make modifications to your system to be compatible with Sensi, but it's best to involve a professional to add the needed transformer and relays.
Remote Sensors
If you have remote sensors, the Sensi thermostats may still be compatible with your system. They will just be incompatible with the sensors, and you will not install the sensor wires to the thermostat.
If you have a Sensi Touch 2 smart thermostat, it is compatible with the wireless Sensi Room Sensors only. Any outdoor or wired sensors are not compatible.
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