You've raised a good point about GFCI protection for remote buildings. Here's a breakdown of the issues and why you have reason for concern

Key Concerns Regarding GFCI Functionality and Distance:
Increased Ground Fault Path Impedance

The fundamental problem with long runs of UF cable to outbuildings and GFCI protection is the increased impedance of the ground fault path. 200 feet of conductor significantly increases the resistance and inductance of the ground path.

GFCI Trip Threshold

A GFCI device is designed to trip when it detects a difference in current between the ungrounded (hot) and grounded (neutral) conductors of 5mA (milliAmps) or greater. This difference indicates that current is leaking to ground – a potential shock hazard.

Impact of Impedance

With a long run, if a ground fault occurs at the outbuilding, the impedance of the ground fault path might be high enough that the current flowing back to the GFCI receptacle at the main house is less than the 5mA trip threshold. In this scenario, the GFCI will not trip, leaving the outbuilding circuit unprotected during a ground fault.

Nuisance Tripping

Conversely, long runs of UF cable are more susceptible to induced currents and stray voltage. These can sometimes cause nuisance tripping of the GFCI, even when there isn't a true ground fault.

Voltage Drop exacerbates the issue

The 200 foot run using 10 AWG wire suggests that the homeowner is very concerned about voltage drop. Voltage drop will also effect the efficiency of a ground fault if one should occur.

Why a Standard Circuit Breaker is Insufficient

A standard 20-amp circuit breaker provides overcurrent protection. It will trip if the circuit is overloaded (drawing more than 20 amps) or if there's a short circuit (a direct connection between the hot and neutral wires). However, a standard breaker will not trip for a low-level ground fault current that is below its tripping threshold. This is the critical difference between overcurrent protection and ground fault protection.

Specific Answer to Your Questions


Distance and GFCI Capability

There isn't a specific, hard-coded distance limit in the NEC where a GFCI guaranteed to fail. However, the NEC does recognize the impact of impedance on ground fault protection. The effectiveness of a GFCI decreases as the length of the circuit increases due to the factors mentioned above. The longer the run, the higher the impedance, and the greater the risk that a ground fault will not cause the GFCI to trip.2.

Circuit Breaker Protection

As stated above, a standard circuit breaker is not a substitute for GFCI protection. It protects against overcurrent and short circuits, but not against low-level ground faults.

Relevant Code Considerations (NEC - Consult the latest edition)



NEC 250.32 (Grounding and Bonding of Detached Buildings)

This section outlines the requirements for grounding and bonding at detached buildings. It's crucial to ensure proper grounding at the outbuilding to provide a low-impedance ground fault path back to the main service. Depending on the specific installation, this may require a grounding electrode system (ground rod) at the outbuilding.

NEC 250.4(A)(5) (Impedance)

"The earth shall not be considered as an effective ground-fault current path." While a ground rod at the outbuilding is required, it's not intended to be the sole path for ground fault current. The equipment grounding conductor (the ground wire in the UF cable) must be run with the circuit conductors.

NEC 210.8(A) and (B) (GFCI Protection)

These sections dictate where GFCI protection is required. While the receptacle on the outside of the house needs to be GFCI protected, it doesn't necessarily mean it's the best method for protecting the entire circuit to the outbuilding.

Inspection Concerns and Recommendations



Evaluate the Ground Fault Path

Carefully inspect the grounding and bonding at both the main house and the outbuilding. Ensure a proper equipment grounding conductor is run with the circuit. Verify the connection to the grounding electrode system (if required) at the outbuilding.

Voltage Drop

Verify the voltage drop calculation to ensure compliance. While the homeowner is attempting to mitigate voltage drop, it's good practice to verify the values.*

Consider Alternatives for GFCI Protection

While not code advice, consider this from an inspection stand point. Due to the distance of the run, ask your self if the installation could have been done differently and if that alternative would have made more sense.

Important Disclaimer: I am an AI chatbot and cannot provide official electrical code interpretations. Always consult the latest edition of the NEC and consult with qualified electrical professionals for specific installation requirements. Flag for review