Installation

When I use the wire picker in the Sensi mobile app, what if my wire is not listed or my configuration is invalid?

If you entered your wires into the wire picker and it said to select a valid configuration or your wires were not listed, Sensi may not be compatible with your current system. See below for common wiring issues.

"C"/Common Wire

C Wire Required

Depending on the Sensi model you're installing and your system type, you may need to install a C wire. Learn more about which applications require a “C” wire on our compatibility page.

Common wire with uncommon label

• B Wire without a C terminal - If you do not have a heat pump then this wire is typically used for C. Please research your current thermostat manual for information. 
• X - The X wire could be a C wire please research your current thermostat manual for more information. 

Incompatible wire labels

Some systems are not compatible with Sensi.

• Line voltage – If you have thick gauge wires or have no wire labels you many have a line voltage HVAC system. Sensi thermostats are not compatible with line voltage systems.
• Communicating systems – Sensi thermostats are not compatible with this type of wiring. Contact your current thermostat manufacturer for compatible replacement thermostats.
  • A, B, C
  • 1, 2, 3
  • V+, V-

Remote indoor/outdoor sensors

Sensi thermostats are not compatible with wired or other manufacturer sensors. You can potentially install Sensi without your current sensor wires but removing them may affect your system performance.

• S1, S2
• RS +/-
• RS1, RS2
• T

Zone panel control

If you have more than one thermostat in your home, but only one HVAC system, you may have a zone control system. If you have O and B wires on your original thermostat, but don’t have a heat pump, you may have a zone control system.

If you have separate O and B wires with a zone control system, Sensi will not be compatible with your system. To make Sensi compatible you will need to combine your O and B wires at your zone panel. Refer to your zone control manufacturer for options.

Honeywell Wire Saver Module

If you have a “K” wire on your Honeywell thermostat, you likely have a Honeywell Wire Saver Module installed at your HVAC system. Label the “K” wire as “Y” on Sensi.

Note that you may lose the ability to independently control the fan on your HVAC system.

Modulating furnaces

If your original thermostat controlled the modulation on your furnace, you may have a “V” wire. Sensi thermostats do not control modulation. If you install the Sensi, you will lose the modulating function of your HVAC system, which may affect system performance.

If you still want to install Sensi, tape off the “V” wire, push it back in the wall, and do not enter it in the wire picker.

Humidity control

If your original thermostat had wired humidification or dehumidification controls, you may have wire labels like:

• HUM
• DEHUM
• ACC+/-
• H1/H2
• DH1/DH2

While some Sensi models are compatible with wired humidity control, you should refer to a HVAC professional for setup. After installation, a professional can test to make sure the humidity control is operating as expected.

Auxiliary/Emergency heating systems

A heat pump with back-up auxiliary/emergency heat may have two wires for the same function (“AUX” and “E” or “W” and “E”).

Depending on your system wiring, these may control the same single stage furnace. Alternatively, one may be for first stage auxiliary heating, and the other may be for second stage auxiliary heating. Refer to your original thermostat’s manual to determine the difference between the two terminals. If you aren’t sure, you may want to have a professional HVAC technician install the thermostat to ensure proper system performance.

Other wire labels

If your wire is labelled something different from the other labels listed here and not available in the wire picker in the Sensi app, you may need to identify the wire's purpose by referring to your thermostat installer manual. Compare the terminal output designation to the Sensi wiring diagram's output designations to see if they match.

Find a Pro

If you're not comfortable installing, contact an HVAC professional to trace the wire and determine the function. If you install the wires improperly your system could be damaged or not function as expected.