WiremanWireman · Surges and electronics keep failing: troubleshooting for electricians · 2023 NEC ·
Surges and electronics keep failing
TVs, routers, boards and drivers dying. Sort out surges, high voltage, a bad neutral and grounding differences between systems.
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How it works
A surge is a very short voltage spike, from lightning, utility switching or motors and compressors shutting off inside the building. A surge protective device (SPD) clamps the spike and sends the surge current to the neutral and ground, so it works best with short, straight leads at the panel. Type 1 SPDs can go on the line side of the service disconnect, Type 2 on the load side, and Type 3 at the point of use. Not every “surge” failure is a surge: a loose neutral that pushes a leg high for minutes, or cable and phone systems grounded separately from the power system, kill electronics too.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- When does equipment fail?
- After stormsTest: Check the service SPD
- No SPD installedNo surge protection at the service
- SPD shows failed, or the leads are longA spent or poorly installed SPD
- SPD installed and goodTest: Check how other systems are groundedExpect: All systems bonded together at the service, and near 0 V between the shield and the equipment ground.
- Separate grounds, or volts between themCommunications not bonded to the power grounding system
- Bonded together, about 0 VSurges from inside or reaching through other wiring
- Randomly, no stormTest: Record voltage over several daysExpect: Both legs within 114 to 126 V on a 120 V system, staying close to each other.
- One leg goes high when the other is loadedA loose or open neutral
- Both legs run highService voltage running high
- Steady and in rangeTest: Check how other systems are groundedExpect: All systems bonded together at the service, and near 0 V between the shield and the equipment ground.
- Separate grounds, or volts between themCommunications not bonded to the power grounding system
- Bonded together, about 0 VSurges from inside or reaching through other wiring
- Network, cable or phone ports blownTest: Check how other systems are groundedExpect: All systems bonded together at the service, and near 0 V between the shield and the equipment ground.
- Separate grounds, or volts between themCommunications not bonded to the power grounding system
- Bonded together, about 0 VSurges from inside or reaching through other wiring
- When big motors or compressors cycleSurges from loads inside the building
- After stormsTest: Check the service SPD