Error Codes — Mysa for In-Floor Heating
2 min read
Updated February 1, 2026
If your Mysa for In-Floor Heating displays an error code, use this guide to identify the issue and resolve it.
Error Code Reference
| Code | Meaning | Cause |
|---|---|---|
| H2 | Open heating circuit | No heater load detected |
| H3 | GFCI trip | Ground fault detected |
| I3 | Floor sensor issue | Sensor loose, disconnected, or out of range |
H2
MeaningOpen heating circuit
CauseNo heater load detected
H3
MeaningGFCI trip
CauseGround fault detected
I3
MeaningFloor sensor issue
CauseSensor loose, disconnected, or out of range
H2 — Open Heating Circuit
The thermostat detects no heater load on the circuit.
Possible causes:
- Heating mat not connected
- Loose wire connection
- Damaged heating element
How to fix:
- Turn off power at the breaker
- Check that the heating mat wires are securely connected to the LOAD terminals
- Verify the heating mat is not damaged
- Restore power and test
Warning Turn off power at the breaker before checking any wiring connections.
H3 — GFCI Trip
The built-in GFCI detected a ground fault and tripped for safety.
Possible causes:
- Ground fault in the heating mat
- Moisture in the electrical connections
- Damaged wiring
How to fix:
- Press the Reset button on the side of the thermostat
- If it trips again immediately, there may be a ground fault in the system
- Check for moisture or damage in connections
- Contact an electrician if the issue persists
Caution Repeated GFCI trips indicate a potential electrical fault. Do not bypass the GFCI. Have the system inspected by a qualified electrician.
I3 — Floor Sensor Issue
The floor sensor is not reading correctly.
Possible causes:
- Sensor wire disconnected
- Sensor damaged or broken
- Sensor resistance outside the 5K–40K Ohm range
How to fix:
- Turn off power at the breaker
- Check that the floor sensor wires are connected to the sensor terminals
- Verify the sensor wire is not damaged
- If using an existing sensor, confirm it's within the 5K–40K Ohm range
- Recalibrate the sensor in app settings if needed
Tip If you installed a backup sensor during initial setup, you can switch to it without needing to access the floor.
Need Help?
Contact our support team at support@getmysa.com