Wiring Requirements

Gen3 has different electrical ratings from V2 and Lite. Read the ratings below and the Gen3: Electrical ratings and breaker size article before you install.

Mysa for Electric Baseboard Heaters works with 120/208/240 VAC line-voltage systems. The line-voltage wiring must go to the thermostat location first. A complete circuit must be in the gang box, not only at the heater.

Electrical ratings

Mysa sells Gen3 in Canada. V2 and Lite are the current models in the United States.

Model	Maximum current	120 V	208 V	240 V
Gen3	16.7 A	2,000 W	3,400 W	4,000 W
V2 and Lite	16 A	1,900 W	3,300 W	3,800 W

Wire count

You need 4 wires in your gang box: two cables with two wires in each cable, not counting the ground wire. One cable brings power in. One cable goes out to the heater. Usually, wire nuts join the wires in two groups.

• 240 V systems: 2 wires bring power from the breaker (L1 and L2). 2 wires go to the heater.
• 120 V systems: 2 wires bring power from the breaker (line and neutral). 2 wires go to the heater.

Wire type

Use copper wire only. Mysa can't be used with aluminum wiring.

Do not change the existing wiring. If you are not sure about your wiring, call an electrician.

Only see 2 wires?

Remove the old thermostat. Look inside the gang box for more wires. Often, extra wires with wire nuts on their ends are inside the box.

If your gang box has only 2 wires, the thermostat location only breaks the circuit. That location cannot supply power to a smart thermostat. Read When You Only Have 2 Wires for your options, or send an email to install@getmysa.com.

Important: Count all the wires in your gang box, not only the wires on your current thermostat. Many thermostats use only 2 wires, but the box can have more wires.

About 240 V circuits

A 240 V circuit has no neutral. Each wire carries 120 V to ground, including a white wire. A double-pole breaker shows it's 240 V.

How to connect the wires

Mysa has three wire leads: L1 (black), L2/N (red) and Load (black). Connect each lead to the house wires by their function, not by their colour:

1. L1 lead (black): Connect it to the line wire from the breaker.
2. Load lead (black): Connect it to the wire that goes to the heater.
3. L2/N lead (red): Connect it to the second wire from the breaker and the matching wire to the heater. On a 120 V system, these are the neutral wires. On a 240 V system, these are the L2 wires.
4. Ground wire: Mysa doesn't connect to ground. Leave the box's ground wires joined as they are. Don't cut or remove them.

Wire colours are not the same in all homes. Compare your wires with the picture in the install guide. If you are not sure, send a photo of your wires to install@getmysa.com.

Single-pole and double-pole

Mysa for Electric Baseboard Heaters is a single-pole thermostat that can replace many single-pole and double-pole thermostats.

A double-pole thermostat disconnects both legs of a 240 V circuit when it is off. A single-pole thermostat disconnects only one leg.

When Mysa is off, one leg of a 240 V circuit stays live at the heater, at 120 V to ground. Turn off the breaker before you work on the heater. Some regions require double-pole, so check your local code.

Get support

Take a photo of your wiring and send it to install@getmysa.com.