Using a Wired Temperature Sensor with Your Mysa Smart Thermostat

Last updated: July 6, 2026

Your Mysa Smart Thermostat for Central HVAC has a wired temperature sensor input, so you can measure temperature somewhere other than where the thermostat is mounted. This is useful when the wall the thermostat sits on isn't the best place to read the temperature — for example, reading the air in a different part of the room, or reading floor temperature with an in-floor probe.

This feature is only on the Mysa Smart Thermostat for Central HVAC. Mysa Baseboard and Smart Thermostat for AC models do not support a wired temperature sensor.

What You'll Need

  • A Mysa Smart Thermostat for Central HVAC, installed and connected in the Mysa app.

  • A compatible 2-wire NTC thermistor probe with a nominal resistance between 5 kΩ and 40 kΩ. The probe wires connect to the thermostat's S1 and S2 sensor inputs.

  • Your thermostat on a recent firmware version. If your thermostat is up to date, the wired-sensor options appear automatically in the app. If you don't see them, update your thermostat's firmware and check again.

How the Wired Sensor Is Used

The wired sensor reads the temperature at wherever you place it. You can use it two ways:

  • As a room (ambient) sensor — place the probe where you want the thermostat to measure room temperature.

  • As a floor sensor — for in-floor heating, the probe reads floor temperature. This works when the sensor's resistance is set correctly in the app (see below).

Note: The Smart Thermostat for Central HVAC does not use separate "Ambient" and "Floor" modes the way the Mysa Smart Thermostat for In-Floor Heating does. The wired sensor simply reports a temperature; how you use that reading is set with the steps below.

Setting It Up in the Mysa App

  1. Connect your probe's two wires to the thermostat's S1 and S2 inputs.

  2. In the Mysa app, open your thermostat and go to settings -> Thermostat Preferences.

  3. Select Yes for Are you using a wired sensor.

  4. Set the resistance rating to match your probe (any value from 5 kΩ to 40 kΩ). Matching this correctly is what lets the thermostat read your probe accurately.

Choosing Which Sensor Controls Your Heating & Cooling

Connecting a wired sensor lets the thermostat read a second temperature. A separate setting decides which sensor the thermostat actually regulates from:

  • Use as Primary Sensor turned off — the thermostat's built-in sensor controls heating and cooling.

  • Use as Primary Sensor turned on — the wired sensor controls everything. All temperature control and your schedules follow the wired sensor's reading.

Note: This is an all-or-nothing setting — the thermostat regulates from one sensor at a time. For an in-floor setup, turn Use as Primary Sensor on so the thermostat controls from the floor probe.

Troubleshooting

No reading, or the temperature looks far too high or low

This usually points to the probe wiring or the resistance setting. Check that both wires are firmly connected to S1 and S2, and confirm the resistance rating in the app matches your probe (5 kΩ–40 kΩ).

The wired-sensor options don't appear in the app

Your thermostat likely needs a firmware update. Once it's up to date, the options appear automatically.

The reading is off by a few degrees

Some variation is normal and depends on where the probe is placed. Try repositioning the probe to a spot that better represents the temperature you want to measure.

If readings are still wrong after checking the connection and resistance setting, contact Mysa Support.

FAQ

Which sensors are compatible?

Any 2-wire NTC thermistor with a nominal resistance between 5 kΩ and 40 kΩ, connected to the S1/S2 inputs.

Is the wired sensor the same as a wireless room sensor?

No. The wired S1/S2 input is a separate feature from any wireless room/climate sensor. Don't confuse the two — this article covers the wired probe only.

What happens to my sensor settings if I reset or re-pair the thermostat?

Your wired-sensor selection resets. After re-pairing the thermostat, set the wired sensor up again.

Is this available on Mysa Baseboard or AC thermostats?

No. The wired temperature sensor is supported on the Mysa Smart Thermostat for Central HVAC only.