Installation & Wiring Troubleshooting

Last updated: October 27, 2026

This article helps you solve problems after you install Mysa for Electric Baseboard Heaters. Find the problem that you see, then do the steps.

Warning: Installing this product involves handling high voltage wiring. To avoid personal injury, or death, turn off your circuit breakers and follow the proper safety precautions before proceeding.

Turn off the power before completing any electrical installation. Use a voltage tester to make sure that the power is off. We strongly recommend a voltage tester. It is the only reliable proof that the power is off. If you are unsure that the power to your heaters is off, stop work and call an electrician.

The thermostat does not come on

  1. Remove the front plate. Look for the green LED.
  2. If you do not see the green LED: Turn off the circuit breaker. Make sure that the line wire from the breaker is tightly connected to the Mysa L1 lead.
  3. If you see the green LED: Mysa receives power. Keep the front plate off for 3 to 5 minutes. Then put the front plate back on Mysa.

If the display does not come on, contact support.

The heat does not stop

Usually, the cause is a heater wire on the L1 lead instead of the Load lead.

  • The line wire from the breaker connects to the Mysa L1 lead.
  • The heater wires connect to the Mysa Load lead and the Mysa L2/N lead. Do not connect a heater wire to the L1 lead.

Turn off the circuit breaker. Examine your wiring and correct each wrong connection. If the heat does not stop, contact support.

There is no heat

Usually, the cause is a bad connection between the heater wire and the Mysa Load lead.

  1. Turn off the circuit breaker.
  2. Make sure that the heater wire is tightly connected to the Mysa Load lead.
  3. Pull the wire nut gently to make sure that it is tight.

The house wire colours are opposite to usual

In some homes, the house wire colours are opposite to usual. The red or white wires connect to the old thermostat. One wire nut in the gang box holds the black wires together.

Connect each Mysa lead to the house wire by its function, not by its colour:

  • L1 lead: the line wire from the breaker.
  • Load lead: the wire that goes to the heater.
  • L2/N lead: the black wires in that wire nut. Keep these wires together in one wire nut.

The colours of the Mysa leads will not match the colours of your house wires. This is correct. For a picture of this wiring, use the step-by-step installation guide.

If you separated the black wires and you cannot identify each wire, stop work. Send a photo of your wiring to install@getmysa.com.

H2 error code (Gen3, V2 and V1)

Mysa did not detect a heater between Load and L2/N. Lite does not display H2.

  1. Turn off the circuit breaker.
  2. Make sure that the Mysa Load lead connects to the heater wire. The colour of the heater wire is not important.
  3. Make sure that each wire is tight in its wire nut. When a wire nut holds more wires, the wires can become loose.
  4. Turn on the circuit breaker. Make sure that the error code goes away.

Restart Mysa

Hard reboot (all models): Turn off the circuit breaker. Wait 30 seconds. Then turn on the circuit breaker.

Do not hold the up arrow and the down arrow to restart Mysa. This hold resets Mysa:

  • V2, Lite and V1: A hold for 10 seconds resets Mysa. Mysa removes its Wi-Fi, its Apple Home (HomeKit) pairing, its schedule and its settings. Then you must set up Mysa again in the Mysa app.
  • Gen3: On Gen3, the same hold starts a countdown on the screen. When the countdown ends, Gen3 resets its Wi-Fi and removes all its smart home (Matter) connections. Then you must set up Gen3 again in the Mysa app, and add it to your smart home app again.

Get support

Send a photo of your wiring and a photo of the rating plate on your heater. These photos help us give you a fast answer.

Before you remove Mysa from the wall for the wiring photo, turn off the circuit breaker. Make sure that the power is off.