Baseboard heaters are simple electrical units consisting of a heating element with attached metal fins for transferring heat, and a limit control- a switch that prevents the element from overheating. To control the temperature, some models have a built-in thermostat; others are controlled by a line voltage, or zone thermostat-a wall -mounted thermostat that is wired directly to the heater.
Most heaters are wired to a 240-volt circuit, which means both the black and white circuit wires are hot and carry voltage. Others use 120 volts and are wired to a circuit or plugged into a standard receptacle. The tests for all three types are nearly the same.
If the heater is wired to a household circuit, shut off the power at the main service panel, and test for power before proceeding.
Note: Wiring for heaters and thermostats varies. For the best- and safest- results, check the manufacturer’s wiring instructions, and label all wires before disconnecting.
How to Test for Power Before Making Repairs
Turn off the power to the heater at the main service panel. Remove the heater’s control box cover, and label the black hot circuit wire. Insert one probe of a neon circuit tester or multimeter into the wire connector at the end of the circuit wire, and touch the other probe to the grounding screw on the heater casing. Then, label the other circuit wire (with a 240-volt heater, this wire will also carry voltage). Insert the tester probe into its wire connector, and touch the other probe to the grounding screw. Finally, insert one probe into each of the wire connectors you’ve just tested. If the tester shows current for any of the tests, the power is still on. Return to the service panel, and turn off the correct circuit.
How to Test & Service an Electric Baseboard Heater
1. Begin by testing the limit control. Shut off the power at the main service panel, and confirm it is off by testing the unit (page 534) Pull a limit control lead from its terminal. Set multimeter to test continuity Touch one probe to each limit control terminal. If the tester shows continuity, it means the limit control is working correctly, and you should move on to testing the thermostat (step 2). If the tester does not show continuity, remove the limit control and thermal conductor from the unit and replace it with a duplicate part from the manufacturer.
2. To test the thermostat, start by labeling each thermostat lead and wire connected to it giving both wires the same name. Designate circuit wires and their respective leads as HOT, and heater wires and their respective leads as UNIT.
3. Disconnect wires, and remove thermostat. Turn thermostat dial to highest (hottest) setting. Set multimeter to test continuity. Touch one probe to a HOT wire lead and the other to each UNIT wire. The tester should indicate continuity in one of the connections. Repeat test for the other HOT wire lead and each UNIT wire. If there is continuity for both HOT wires, move on to step 4. If the thermostat fails either test, replace with duplicate part from manufacturer.
4. Test the heating element. Find the heating element wire that connects to a thermostat lead. (This wire may come from the far end of the element.) Unscrew wire connector, and separate wires. Set a multimeter to test continuity. Touch one probe to the free heating element wire and the other to the wire running from limit control to the other end of the element. Multitester should indicate continuity, meaning element is sound and the problem may lie in the circuit. If not the element is bad, and the entire unit should be replaced
Learn how to Test & Service an Electric Baseboard Heater