Voltage Troubleshooting
Enter expected and measured voltages to surface likely faults.
Measurements
Nominal: 120, 208, 240, 277, 347, 480
Healthy: < 2 V under load
Line-to-neutral at the device
Voltage within normal range (-1.7%)
Common causes
- System appears healthy. CEC allows ±5% at the outlet under normal conditions.
- Re-check under full load — voltage sag only shows up when current flows.
Common suggestions to fix
- No action needed — document the reading for the service record.
- Re-test under full operating load to confirm voltage holds.
Always lock out, tag out, and verify dead before opening enclosures or making repairs.
Quick reference
Voltage tolerance (CEC)
±5% at the outlet is acceptable for most equipment.
Open neutral signature
One leg high, the other low, total still ≈ 240 V.
Neutral-to-ground
Should be near 0 V at no load and < 2 V under load.
Safety
Always lock out and verify dead before opening enclosures.