Ground-Fault Protection of Equipment: 230.95 Rules and Testing

Ground-fault protection of equipment, or GFPE, is required by the National Electrical Code on every solidly grounded wye service disconnect rated 1,000 amperes or more where voltage to ground exceeds 150 volts and phase-to-phase voltage stays at or below 600 volts. In practice that means 480Y/277-volt commercial and industrial services. The same thresholds extend to feeders and to branch-circuit disconnects at that rating, and to the main disconnect of a separate building served by a qualifying system. The protection must pick up at no more than 1,200 amperes, must clear a fault of 3,000 amperes or more within one second, and must be performance-tested on site when it is first installed.¹

Those are the headline rules. The details below walk through where in a distribution system GFPE applies, where the Code excludes or prohibits it, the specific settings and coordination requirements, and the testing and documentation an authority having jurisdiction will expect to see.

The Core Threshold Under NEC 230.95

Article 230.95 is the anchor rule. It applies when four conditions are met together: the system is solidly grounded wye, voltage to ground is more than 150 volts, phase-to-phase voltage is 600 volts or less, and the disconnect is rated 1,000 amperes or more.¹

A 480Y/277-volt service at 1,200 amperes meets all four, so GFPE is required. A 208Y/120-volt service at the same amperage does not, because voltage to ground is only 120 volts. A delta service, grounded or not, is excluded because it isn’t wye. A resistance- or impedance-grounded system is excluded because it isn’t solidly grounded. These are not technicalities; they are the four facts to confirm before deciding whether GFPE is in scope at all.

Where GFPE Is Required Downstream of the Service

The requirement doesn’t stop at the service entrance. Article 215.10 extends the same voltage and ampere thresholds to feeders, and Article 210.13 does the same for branch-circuit disconnects rated 1,000 amperes or more on qualifying systems.² Article 240.13 adds a separate requirement for any disconnect rated 1,000 amperes or more on a 480Y/277-volt system that acts as the main disconnect for a separate building or structure.¹

A 1,200-ampere feeder running to a warehouse across a parking lot carries the same GFPE obligation as the service that feeds it. The thresholds travel with the current rating and the voltage class, not with the location.

Where GFPE Is Not Required, or Is Prohibited

The Code carves out a meaningful set of situations. Installing GFPE where it isn’t needed invites nuisance trips; omitting it where it is needed fails inspection.

Fire pumps. NEC 695.6(G) prohibits GFPE on fire pump circuits. A fire pump that trips during a ground fault could leave sprinklers without pressure during a fire.
Emergency and legally required standby systems. The alternate power source for emergency systems (NEC 700.27) and legally required standby systems (NEC 701.26) does not need automatic ground-fault disconnection. Emergency sources must provide ground-fault indication when automatic disconnection isn’t used.
Continuous industrial processes. Where an abrupt power loss would create a greater hazard than the fault itself, automatic disconnection may be omitted and replaced with a ground-fault alarm so operators can manage a controlled shutdown. Facilities relying on this exception should document the specific hazard that an unplanned shutdown would create, because inspectors frequently challenge it.¹
Services split into smaller disconnects. A 4,000-ampere service split into five 800-ampere disconnects under NEC 230.71 keeps every individual disconnect below the 1,000-ampere threshold, so none of them triggers the rule.
Delta and non-solidly-grounded systems. Delta configurations and resistance- or impedance-grounded systems fall outside Article 230.95 entirely.
208Y/120-volt systems. Even at high amperage, voltage to ground stays at 120 volts, below the 150-volt trigger.
Temporary generator connections. Feeders temporarily connecting a generator during repairs or emergencies can skip GFPE for up to 90 days.

Second-Level Protection in Health Care Facilities

Hospitals and other health care facilities have a layered rule under NEC 517.17. When GFPE is installed on the main service or feeder of a health care facility, a second level of ground-fault protection must also be installed on the next downstream level of feeders, and the two must be selectively coordinated so a fault on a downstream feeder trips only the downstream device.³ The minimum separation between the time bands of the feeder and main ground-fault relays must be at least six cycles, roughly 100 milliseconds at 60 Hz.

The intent is to keep a single fault from blacking out an entire wing. If the service or feeder doesn’t meet the thresholds that would trigger mandatory GFPE in the first place, 517.17 doesn’t apply, and no downstream ground-fault protection is required either.³

Pickup, Time Delay, and Coordination

Two settings govern how a GFPE system responds. Pickup is the ground-fault current level at which the relay operates. NEC 230.95 caps pickup at 1,200 amperes. Time delay is how long the relay waits after detecting a fault before commanding the breaker open. For faults at or above 3,000 amperes, the maximum delay is one second.¹

The time delay exists so that downstream devices can clear a fault before the upstream main trips. In a building with GFPE on both the service and a feeder, the feeder is given a shorter delay and trips first, isolating the fault without killing power to the rest of the building. The main waits slightly longer and acts as backup if the feeder’s protection fails. The manufacturer’s time-current curves are the working tool for setting these intervals so they don’t overlap.

Settings that are too sensitive cause nuisance trips, which in a commercial building can corrupt data, strand elevators, and shut down ventilation. Settings that are too loose defeat the point of the protection. The correct values depend on the system’s normal leakage current, the available fault current, and the coordination requirements with devices above and below in the chain.

Lower-Threshold Requirements for Heating and De-Icing

Beyond service disconnects and feeders, the Code requires ground-fault protection at much lower current levels for specific equipment. NEC 426.28 mandates GFPE for fixed outdoor electric de-icing and snow-melting equipment, and NEC 427.22 requires it for fixed electric heating and heat-tracing systems. These operate in the milliampere range because the heating cables themselves are what the protection is guarding, against insulation degradation and leakage that can start a fire in a roof, gutter, or pipe chase.

The NEC doesn’t fix a specific milliampere threshold for these applications. Industry practice has settled on 30 milliamperes as a common factory default, with adjustable devices sometimes set higher on long cable runs that have inherently higher leakage.

Required Performance Testing at Installation

NEC 230.95(C) requires every GFPE system to be performance-tested on site when first installed, following the manufacturer’s instructions.⁴ This is not paperwork. Sensors can be damaged in shipping, wiring can be landed with reversed polarity, and neutral-to-ground bonds can end up in the wrong place. None of those defects are visible without a live test.

Primary current injection is the accepted method. A test set pushes controlled current through the sensors, verifies that the relay picks up at the correct threshold, and confirms that the breaker opens within the required delay. The test exercises the full chain: sensor, relay, wiring, shunt-trip coil, and breaker mechanism. Some trip units offer a built-in secondary test that checks relay logic without injecting current; that function is useful for quick verification, but it does not confirm sensor accuracy or breaker operation and does not satisfy initial commissioning.

A written record of the test must be made available to the authority having jurisdiction.⁴ Many jurisdictions will not issue a certificate of occupancy or authorize the utility to energize the service without that documentation. The report should list the date, the technician’s name and qualifications, the relay settings, the test current applied, and the measured trip time. The same record becomes the baseline for every future maintenance test.

Who Can Perform the Testing

The NEC requires performance testing but does not specify who may perform it. Inspectors and owners typically expect demonstrated competence in power-system testing. The InterNational Electrical Testing Association’s four-tier certification under ANSI/NETA ETT is the common industry benchmark.⁵

Level 1, Trainee: entry-level, works under direct supervision of a Level 3 or Level 4 technician.
Level 2, Certified Assistant: performs limited testing under supervision; two years of experience and 200 hours of combined safety and electrical training.
Level 3, Certified Technician: supervises others and evaluates test data; five years of experience and 464 hours of training.
Level 4, Certified Senior Technician: manages large projects independently and prepares written reports; ten years of experience and 704 hours of training.

For commissioning on a major 480-volt service entrance, a Level 3 or Level 4 technician is the practical floor.

Keeping the System Compliant Over Time

The NEC requires performance testing at installation but does not prescribe a recurring interval. That silence is not permission to skip ongoing testing. NETA’s Maintenance Testing Specifications (ANSI/NETA MTS) lay out detailed procedures for periodic GFPE maintenance, and many insurers and facility operators adopt them as their standard.⁶

A thorough periodic inspection covers both visual-mechanical and electrical work: verifying sensor polarity, confirming that grounding conductors do not pass through zero-sequence sensors, checking that neutral connections sit on the source side of any ground-fault sensor, inspecting bolted connections for high resistance, performing primary current injection to verify pickup, measuring the time delay at 150 percent or more of pickup, verifying neutral-to-ground insulation resistance with the neutral disconnect link temporarily removed, and confirming reduced-voltage tripping.

OSHA’s requirements under 29 CFR 1910.304 reinforce the documentation obligation. The regulation primarily addresses assured equipment grounding conductor programs rather than GFPE specifically, but it establishes the principle that test records must identify the equipment and the date and must be available for inspection.⁷ A facility that cannot produce GFPE test records after an electrical fire is in a difficult position with both regulators and insurers, regardless of whether the system was in fact working at the time.

1
Eaton. Ground-Fault Protection of Equipment
2
Electrical Contractor Magazine. Performance Testing and the NEC
3
Eaton. NEC 517.17 Selectivity
4
Eaton. Performance Testing for Ground Fault Circuit Breakers
5
InterNational Electrical Testing Association (NETA). Technician Certification
6
InterNational Electrical Testing Association (NETA). ANSI/NETA MTS-2007 Standard for Maintenance Testing Specifications
7
Occupational Safety and Health Administration. 1910.304 – Wiring Design and Protection