Line-voltage thermostats operate at either 120 or 240 volts and control gable vent fans, electric baseboard heaters, and similar appliances. Replacing them is different but no harder than replacing a furnace thermostat. There is one important—and potentially dangerous—difference between the two, however. A conventional low-voltage thermostat operates at 24 volts. An electric baseboard heater may operate at 240 volts. Always make sure the power is off when working on either type of thermostat, but be doubly cautious with a line-voltage thermostat. Warning: Before you begin, turn off power to the circuit.
