The Model FTA2A thermostat manufactured by Fahrenheat/Marley conforms with U.S. electrical code. It is a double-pole thermostat, which means it has two temperature-controlled circuit interrupters. It regulates both lines that feed power to a heater. Installing a thermostat to a baseboard heater is energy-efficient and convenient because you can turn it on selectively. Installation time may vary from 30 to 45 minutes.
Turn off electrical power to the baseboard heater at the main circuit breaker box.
Choose which end of the baseboard heater you want to install the FTA2A thermostat. Each end of a baseboard heater has a metal plate cover for the exact size of the FTA2A thermostat. Use a six-in-one screwdriver to remove the screw holding one of the metal plates.
Verify that the heater receives no electrical power by using a 220-volt light tester. Connect the light tester's two probe wires to L1 and L2, romex wire at the back of the heater that supplies the main electrical power to the heater. If the light tester shows no light, then the electrical power is off.
Familiarize yourself with the FTA2A thermostat. Check the diagram that came with the thermostat; it shows how the thermostat works. The "housing" is the frame of the heater, identified in the diagram with a point, and it is labeled as a ground. Power is identified as wires L1 and L2 (referring to power in), with a ground identified with two lines and a dot (a bare wire). Two wires are drawn like circular lines; they represent the heater core and are classified as the load or the heating element of the heater. The thermostat has five wires; two wires are red, two wires are black and one wire is green.
Twist one of the thermostat's two red wires with the L1 wire. Connect the second red wire with one heater core wire. Twist one of the thermostat's two black wires with the L2 wire. Twist the second black wire with the remaining heater core wire. Cover each of the four connections you just made with a wire connector. Screw the green wire to the housing of the heater. This process grounds the cover plate.
Fasten the loose cover plate to the heater with the screw provided. Turn on the circuit breaker, and test the heater.