WiremanWireman · Baseboard or wall heater not working: troubleshooting for electricians · 2023 NEC ·
Baseboard or wall heater not working
Breaker and both legs, voltage at the heater, the line-voltage thermostat, then the element and limit.
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How it works
Electric baseboard and wall heaters are resistance elements, usually 240 V (some are 120 V). They’re controlled by a line-voltage thermostat, on the heater or on the wall, that switches the full heater current. A single-pole thermostat opens one leg; a double-pole one opens both and has a true off position. Each heater has an automatic-reset high limit that opens if it overheats, often because furniture or drapes block it. Wall heaters add a fan.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What’s happening?
- One heater gives no heatTest: Measure voltage at the heaterExpect: The heater’s rated voltage: about 240 V (or 208 V or 120 V).
- Full voltage, no heatTest: Test the element and limitExpect: About R = V² ÷ W: 57.6 Ω for 1,000 W at 240 V, 38.4 Ω for 1,500 W. Limit closed when cool.
- Element reads OLBurned-out element
- Limit open when coolFailed high limit
- Both normalLoose or burned connection in the heater
- 0 V, or only one legTest: Check the thermostatExpect: Full voltage on the line side and on the load side.
- Voltage in, none outFailed line-voltage thermostat
- No voltage in, or one leg missingOpen wiring or a lost leg
- Full voltage, no heatTest: Test the element and limitExpect: About R = V² ÷ W: 57.6 Ω for 1,000 W at 240 V, 38.4 Ω for 1,500 W. Limit closed when cool.
- All heaters on a circuit are outCheck the 2-pole breaker for the heaters. What do you find?
- Tripped, and it trips againShort, ground fault or overloaded circuit
- Was off or tripped, works nowBreaker was off or tripped
- On and not trippedTest: Measure voltage at the heaterExpect: The heater’s rated voltage: about 240 V (or 208 V or 120 V).
- Full voltage, no heatTest: Test the element and limitExpect: About R = V² ÷ W: 57.6 Ω for 1,000 W at 240 V, 38.4 Ω for 1,500 W. Limit closed when cool.
- Element reads OLBurned-out element
- Limit open when coolFailed high limit
- Both normalLoose or burned connection in the heater
- 0 V, or only one legTest: Check the thermostatExpect: Full voltage on the line side and on the load side.
- Voltage in, none outFailed line-voltage thermostat
- No voltage in, or one leg missingOpen wiring or a lost leg
- Full voltage, no heatTest: Test the element and limitExpect: About R = V² ÷ W: 57.6 Ω for 1,000 W at 240 V, 38.4 Ω for 1,500 W. Limit closed when cool.
- Heats, but weaklyWrong voltage or blocked airflow
- Won’t shut offThermostat contacts stuck closed
- Cycles on and off, or smells hotHeater overheating and cycling on its limit
- One heater gives no heatTest: Measure voltage at the heaterExpect: The heater’s rated voltage: about 240 V (or 208 V or 120 V).