How to Wire a Line-Voltage Thermostat for a Baseboard Heater

Baseboard heaters provide supplemental heating for rooms. Unlike a central furnace, baseboard heaters use line voltage electricity to generate heat. To control baseboard heaters, you need a line voltage thermostat. Wiring a line voltage thermostat allows you to adjust the temperature and turn the heater on and off automatically. With the right materials and basic electrical skills, you can wire a line voltage thermostat for a baseboard heater.

What You’ll Need

Before wiring the thermostat, make sure you have the necessary materials:

  • Line voltage thermostat compatible with baseboard heaters
  • Screwdriver
  • Wire strippers
  • Electrical tape
  • Baseboard heater junction box

The line voltage thermostat should be rated for at least 15 amps at 120-240 volts. Check the electrical specs of your baseboard heater to match the thermostat voltage. The junction box provides access to the wiring connections for the baseboard heater.

Turn Off Power to the Circuit

The first step is to turn off power to the baseboard heater circuit. Locate the circuit breaker that controls the power to the baseboard heater and switch it to the OFF position. Verify power is off by testing with a non-contact voltage tester. Turning off power prevents electric shock while wiring the thermostat.

Remove Old Thermostat (If Applicable)

If there is an existing manual thermostat or thermostat wiring, remove it from the junction box before wiring the new line voltage thermostat. The line voltage thermostat will have its own wiring that needs to connect to the heater wires.

Connect Thermostat Wires

There are typically only two connections needed for a line voltage thermostat:

  • Line/Hot wire
  • Load/Switched wire

The line wire brings power from the circuit breaker to the thermostat. This is usually a black wire. The load wire carries power from the thermostat to the heater itself. The load wire acts as a switch to turn the heater on and off.

Strip 1/2 inch of insulation from the ends of the thermostat wires. Connect the wires to the matching terminals on the baseboard heater junction box using a screwdriver. Attach the line wire to the power input terminal and the load wire to the output terminal that leads to the heater. Consult the thermostat wiring diagram for details.

Use wire nuts to secure the connections. Wrap electrical tape around the wire nuts to prevent them coming loose.

Mount the Thermostat

Mount the thermostat on the wall near the baseboard heater according to the manufacturer instructions. Many line voltage thermostats mount directly to a standard electrical box. Pass the wiring through the electrical box and secure it with the included screws.

Turn Power Back On

With all the wiring complete, turn the circuit breaker back on to restore power. Make sure the thermostat installation works by raising the temperature setting and verifying the baseboard heater turns on. Adjust the temperature lower and check that the heater turns off accordingly.

Set Thermostat Schedule

Program the thermostat schedule for automatic temperature adjustments. Set different temperatures for morning, day, evening and night settings. The thermostat will turn the heater on and off automatically based on the programmed schedule.

Testing and Troubleshooting

If the baseboard heater does not turn on when raising the thermostat setting, recheck the wiring:

  • Confirm the line and load wires are securely connected
  • Verify the line wire is connected to the power input terminal
  • Check that the load wire runs between the thermostat and heater
  • Inspect for any loose wire connections
  • Test the thermostat and heater separately to isolate the issue

Wiring a line voltage thermostat provides convenient control over a baseboard heater. Follow basic safety procedures and use the correct gauge thermostat wiring to avoid overheating and electrical hazards. With the proper wiring in place, the thermostat will regulate the baseboard heater for years of comfortable supplemental heating.

Frequently Asked Questions

What wire gauge should be used to wire a line voltage thermostat?

Use 16 or 18 gauge thermostat wire to connect a line voltage thermostat to a baseboard heater. The wiring needs to be heavy enough gauge to carry 15-20 amp electrical loads safely.

Can I put multiple baseboard heaters on one thermostat?

You can wire multiple baseboard heaters to one line voltage thermostat, but the combined amp load of the heaters should not exceed the thermostat rating. Consult an electrician if wiring multiple heaters on one circuit.

Where should I mount the line voltage thermostat for a baseboard heater?

Mount the thermostat about 5 feet above the floor on an interior wall around 10 feet away from the heater itself. Avoid exterior walls or walls next to air vents or drafts.

How do I adjust the temperature range on my baseboard heater thermostat?

There are dials or switches on most line voltage thermostats to adjust the minimum, maximum, and cycle temperature range in degrees Fahrenheit. Consult the manufacturer instructions.

Can I use a battery-powered thermostat for a 240-volt baseboard heater?

No, battery thermostats only switch low voltage, like in an HVAC system. For line voltage heaters, you need a thermostat rated for 240 volts.

How do I set a programmable schedule on a baseboard heater thermostat?

Refer to the manufacturer instructions for your model. Typically you can set at least 4 time and temperature settings for different periods like morning, day, evening, and night.


Installing a line voltage thermostat provides temperature control for electric baseboard heaters. Following basic wiring safety such as turning off circuit power and using heavy gauge wire allows for proper installation. Programming custom heating schedules maximizes efficiency. With a line voltage thermostat installed, you can enjoy convenient heating automation using your existing baseboard heaters. Just be sure to size the thermostat properly for the electric load and confirm safe, secure wiring.