Electrician Red Seal · Question
A technician is troubleshooting nuisance tripping of a ground fault circuit interrupter (GFCI) protecting an outdoor receptacle. Using a clamp-on ammeter around the phase and neutral conductors feeding the GFCI, they measure 0.5 A flowing through phase and 0.45 A flowing through neutral. What is the MOST likely cause of the nuisance tripping?
A clamp-on ammeter reading of 0.5 A on phase and 0.45 A on neutral indicates a difference of 0.05 A (50 mA) between the two conductors. GFCIs typically trip at
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Question: A technician is troubleshooting nuisance tripping of a ground fault circuit interrupter (GFCI) protecting an outdoor receptacle. Using a clamp-on ammeter around the phase and neutral conductors feeding the GFCI, they measure 0.5 A flowing through phase and 0.45 A flowing through neutral. What is the MOST likely cause of the nuisance tripping?
Answer options: ✅ A small leakage current to ground downstream of the GFCI.
- An overload condition on the protected circuit.
- Voltage fluctuations on the incoming power supply.
- A faulty GFCI receptacle that needs replacement.
Correct answer: A small leakage current to ground downstream of the GFCI.
Explanation: A clamp-on ammeter reading of 0.5 A on phase and 0.45 A on neutral indicates a difference of 0.05 A (50 mA) between the two conductors. GFCIs typically trip at 4-6mA of differential current. This difference suggests that current is leaving the phase conductor and returning to ground through an unintended path downstream of the GFCI, which is exactly what a GFCI is designed to detect and trip on. Overloads or voltage fluctuations do not typically cause this type of current imbalance.
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