LVQ Panel Questions - GFCI

Explain the function of a Ground Fault Circuit Interrupter.

To detect current imbalance between hot & neutral and open the circuit.

Identify the current trip threshold for a GFCI designed for personnel protection.

5 mA

Describe the current trip threshold of a GFCI breaker for equipment protection. Explain what would happen if this device were installed to provide personnel protection.

30 mA

People could receive a potentially fatal shock without the GFCI tripping

Using a hand sketch of a GFCI circuit diagram, explain the theory of operation for a GFCI breaker or receptacle.

Hand sketch of two conductors with current transformer around BOTH phases.

If the same amount of current flowing to the load on the hot wire does NOT come back on the neutral, the GFCI will trip.

Explain how the test circuit in a GFCI works. Determine if a GFCI can be tested de-energized.

Test circuit drains a small amount of current (> 5 mA) from the circuit and trips the GFCI.

GFCI cannot be tested de-energized.

Identify the physical locations requiring a GFCI according to the National Electrical Code (include residential, commercial, and industrial settings).

Garages, Outdoors, Kitchens, Bathrooms, Hot Tubs, Pools, (anywhere within 10 ft of water source). Commercial and Industrial areas where portable cord-connected devices are used (except for office areas)

Identify the tasks requiring a GFCI according to NFPA 70E.

Testing of GFCI’s required by 70E.

Installation Requirements set by NEC.

Required In areas that have high risk of water, moisture, or earth ground contact

Explain why a GFCI will trip on a ground fault but not a short circuit.

Short circuit has all the current going to the load on the hot wire and returning from the load on the neutral – so NO current imbalance.

A ground fault lets current out of the normal circuit path – so Current Imbalance trips the unit.

Determine if any of your department substation breakers have Ground Fault protection. If so, explain the sensing mechanism for the ground fault and determine if this is for personnel or equipment protection.

No

Explain why a GFCI receptacle will function properly to provide personnel protection, even if a dedicated ground conductor is wired to the receptacle.

The ground wire is not in the sensing circuit. [Sensing circuit only uses the Hot & Neutral.] Doesn’t matter if ground is there or not for the GFCI to work.

Explain the testing requirements for a GFCI and why testing is important.

Test every month.

Legally required.

Explain what a Arc Fault Circuit Interrupter is and how it works.

Arc Fault interrupter senses the varying current spikes and trips based on a threshold set by the manufacturer.