WiremanWireman · Fire alarm panel trouble: ground fault: troubleshooting for electricians · 2023 NEC ·
Fire alarm panel trouble: ground fault
Notify first, then isolate circuits at the panel and split the faulted circuit to find where it touches ground.
Before you start
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How it works
Fire alarm circuits are not connected to ground at all. The panel watches for any current leaking from a circuit conductor to ground, and when it finds one it shows a ground fault trouble. A single ground fault usually doesn’t stop the system, but a second one can create a false path or kill a circuit. In many places this work requires licensed fire alarm personnel, and the monitoring company and the authority having jurisdiction (AHJ) must be told before anything is taken offline or tested.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- Are you licensed or authorized to work on this system, and have the monitoring company and owner been notified?
- Yes, notified and in testDid the trouble start after recent work, rain, or a new device install?
- After work in a known areaDamage from recent work
- After rain or a leakTest: Isolate circuits at the panel
- Clears with one circuit offTest: Measure the circuit to groundExpect: Open (OL) or very high resistance on every conductor.
- A reading to ground on a conductorTest: Split the circuit to find the section
- At a device or boxFaulted device or box
- In the cable between devicesDamaged cable between devices
- Shield or drain wire to groundShield or drain grounded in the wrong place
- All open nowFault that comes and goes
- A reading to ground on a conductorTest: Split the circuit to find the section
- Never clears with all field wiring offFault in the panel or its power wiring
- Clears with one circuit offTest: Measure the circuit to groundExpect: Open (OL) or very high resistance on every conductor.
- No clear triggerTest: Isolate circuits at the panel
- Clears with one circuit offTest: Measure the circuit to groundExpect: Open (OL) or very high resistance on every conductor.
- A reading to ground on a conductorTest: Split the circuit to find the section
- At a device or boxFaulted device or box
- In the cable between devicesDamaged cable between devices
- Shield or drain wire to groundShield or drain grounded in the wrong place
- All open nowFault that comes and goes
- A reading to ground on a conductorTest: Split the circuit to find the section
- Never clears with all field wiring offFault in the panel or its power wiring
- Clears with one circuit offTest: Measure the circuit to groundExpect: Open (OL) or very high resistance on every conductor.
- NoNotify first, or bring in the licensed fire alarm technician
- Yes, notified and in testDid the trouble start after recent work, rain, or a new device install?