WiremanWireman · Hot tub heater or GFCI trips: troubleshooting for electricians · 2023 NEC ·
Hot tub heater or GFCI trips
Wiring the GFCI, failed heater elements, wet components, and heaters that won’t heat.
Before you start
How much electrical experience do you have?
This sets how much detail each step shows. You can change it any time.
Showing detail
How it works
A hot tub runs pumps, a heater, lights and controls from one GFCI-protected supply, usually 240 V with a neutral for the 120 V parts. The GFCI compares the current on the hots and the neutral, so the neutral has to pass through it and must never touch ground after it. The most common cause of trips when the heater comes on is a heater element whose sheath has cracked, letting current leak to the water and ground.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What is happening?
- GFCI trips the instant it’s resetTest: Check the GFCI wiring and the neutral
- Neutral miswired or touching groundNeutral miswired at the GFCI or spa
- Holds with spa disconnectedTest: Unplug spa components one at a time
- Clears with the heater outTest: Test the heater elementExpect: Insulation in the hundreds of megohms or more. Resistance close to the calculated value (about 10.5 Ω for a 5.5 kW element at 240 V).
- Low insulation readingLeaking heater element
- Open across the terminalsBurned-out element
- Both normalControl pack fault or wet pack
- Clears with another part outLeaking pump, light, ozonator or blower
- Never clearsControl pack fault or wet pack
- Clears with the heater outTest: Test the heater elementExpect: Insulation in the hundreds of megohms or more. Resistance close to the calculated value (about 10.5 Ω for a 5.5 kW element at 240 V).
- Trips even with no loadBad GFCI
- Trips when the heater comes onTest: Test the heater elementExpect: Insulation in the hundreds of megohms or more. Resistance close to the calculated value (about 10.5 Ω for a 5.5 kW element at 240 V).
- Low insulation readingLeaking heater element
- Open across the terminalsBurned-out element
- Both normalControl pack fault or wet pack
- Trips when a pump or the light comes onLeaking pump, light, ozonator or blower
- No trip, but it won’t heatHeater not called or locked out
- GFCI trips the instant it’s resetTest: Check the GFCI wiring and the neutral