How to Wire a 3-Phase, 3-Pole GFCI Breaker in a 3-Φ Panel

Electrical Technology

How to Install a Three-Phase, 3-Pole GFCI Breaker with and without Neutral

A 3-phase, 3-pole Ground-Fault Circuit Interrupter (GFCI) breaker is used to provide ground-fault protection for three-phase loads supplied from a 120/208V, 3-phase, 4-wire wye (Y) o any other three-phase supply system. These breakers are commonly installed in commercial and industrial distribution panels to protect equipment such as motors, HVAC units, commercial kitchen appliances, pumps, and specialty receptacles located in wet or hazardous environments.

Unlike standard 3-pole circuit breakers, a 3-pole GFCI breaker continuously monitors the vector sum of current in all phase conductors (and neutral, if present). If an imbalance exceeding the GFCI trip threshold is detected, it indicates leakage current to the ground, hence, the GFCI breaker trips and disconnects all ungrounded conductors simultaneously.

Characteristics:

Number of Poles: 3-pole – connects to three lines (L1, L2 & L3), i.e. all hot conductors Hot 1, Hot 2 & Hot 3 (black, red & blue). All lines are mechanically and electrically linked together.
Voltage: Operates on and protects 208V, 240V, 480V, or 600V, three-phase branch circuits. (Line-to-Line).
Amperage Rating: Commonly available in 15A to 100A with 65kA of interrupting rating and 5mA to 30mA protection in NEMA 1 & NEMA 3R outdoor enclosures.
Wiring: Three hot conductors from the breaker, a ground wire (+ a neutral if required) from ground/neutral busbar connects to the three-phase branch circuit in a 120V or 240V supply. The built-in white pigtail on the GFCI breaker always connects to the neutral busbar in the main panel.
Operation: Trips when there is an overload, short circuit, or ground-fault even on a single line and trips all ungrounded conductor(s) at once.
Application: Used as per NEC requirement for heavy loads i.e. motors, HVAC, commercial countertops, welders, air-compressors, outlets/receptacles and industrial appliances, especially located in outdoor or wet areas.

NEC Requirements for GFCI Installation

NEC 210.8(A) requires ground-fault circuit-interrupter (GFCI) protection for branch circuits and receptacles installed in specific locations. These locations include, but are not limited to, bathrooms, garages, outdoor areas, basements, kitchens, laundry areas, pools, spas and other similar spaces as identified by the Code.

As per NEC 210.8(B) for non-dwelling units, all receptacles supplied by three-phase branch circuits rated 150V or less to ground and 100A or less must have GFCI protection.

Moreover, per NEC 210.8(D) for specific appliances, GFCI protection is required for branch circuits or outlets (including hardwired equipment) supplying specific appliances rated 150V or less to ground and 60A or less, whether they are single-phase or three-phase.

In addition, the NEC requires GFCI protection for various occupancies, equipment, and special installations throughout the Code. Relevant sections include, but are not limited to, Articles 210.8, 406.3, 424.44, 426.28, 427.22, 511.12, 517.17, 517.20, 525.23, 530.44, 547.28, 555.35, 620.6, 625.54, 680.5, 680.21, 680.22, 680.23, 680.27, 680.32, 680.43, 680.44, 680.51 through 680.59, 680.62, and 680.71.

Wiring a 3-Phase, 3-Pole GFCI Breaker

To install or replace a 3-Phase, 3-Pole GFCI breaker in a three-phase panelboard, follow the following simple steps.

Step 1: Disconnect the Main Power Supply

De-energize the panel and apply lockout/tagout before working. Verify absence of voltage on all bus bars using non-contact tester. Never touch incoming service lugs; they remain energized unless upstream disconnect is open.

Step 2: Verify Panel Configuration

Confirm that the panel is rated for 120/208V, 3-phase, 4-wire wye, 120/208/240V (High Leg) or any other three-phase supply systems such as 480V or 600V.

The three phase load center is equipped with three phase bus bars (A-B-C) viz L1, L2 & L3 and a neutral/ground bus bar where it is grounded and bonded at the service disconnect (not at subpanels).

Step 3: Install the 3-Pole GFCI Breaker

3-Pole GFCI breakers snap over 3 busbars and draw Hot from each busbar. Mount the breaker onto the A-B-C phase bus bars. Ensure the breaker seats fully and locks into place.

Step 4: Connect Phase Conductors (Load Side)

Connect the load conductors as follows:

Phase A (L1) to the breaker terminal A
Phase B (L2) to the breaker terminal B
Phase C (L3) to the breaker terminal C

Tighten all terminals to the manufacturer’s specified torque.

Step 5: Ground & Neutral Connection (If Required)

For 208V, 3-phase loads, 3-pole, 3-wire without neutral, the neutral conductor does not run to the load.

For 208/240V, 3-phase, 3-pole, 4-wire loads with neutral, the neutral conductor from the breaker terminal (not from the neutral busbar) run to the load.

The bulti-in white or gray neutral pigtail in the GFCI is not a load neutral, it powers the GFCI electronics, hence, it must connects to the neutral busbar.

As a last wire connection, connect the Equipment Grounding Conductor (EGC) from the load to the ground bus bar in the 3-phase main panel.

Step 6: Test / Rest & Verify

Restore power and switch the breaker ON. Press the TEST button on the GFCI breaker to verify proper operation as it must trip immediately. Reset the breaker after successful testing.

Wiring Diagram of 3-Phase, 3-Pole, 3-Wire GFCI Breaker in a 3-Φ, 120/208V Panel

The following wiring diagram shows a 20A, 208V, 3-pole, 3-phase GFCI breaker without Neutral in a 120/208V panel used to protect a 208V three-phase appliance.

In a 120/208V system, the neutral pigtail wire must still be connected to panel neutral. If not required, load neutral does not have to be connected on a 208V circuit.

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A 120/208V, 3-Phase 3-Wire Y panel offers:

L1 to L2 = 208V – 1-Phase
L2 to L3 = 208V – 1-Phase
L1 to L3 = 208V – 1-Phase
L1, L2 or L3 (Any 1 Hot) to Neutral = 120V – 1-Phase
L1, L2 & L3 = 208V – Three-Phase

The color codes used for hot conductors in 120/208V are as follows:

L1 = Black
L2 = Red
L3 = Blue
Neutral = White / Grey
Ground = Bare or Green/ with yellow stripe

Wiring Diagram of 3-Phase, 3-Pole, 4-Wire GFCI Breaker in a 3-Φ, 120/208V Panel

The following wiring diagram shows a 100A, 208V, 3-pole, 3-phase GFCI breaker with Neutral used to protect a 208V three-phase branch circuit.

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The same wiring configuration is used for connecting a NEMA 18-60 receptacle rated for 3-phase, 208Y/120V operation. The non-grounding receptacle is supplied through a 3-pole GFCI circuit breaker with a neutral conductor, as shown below.

Wiring Diagram of 3-Phase, 3-Pole, 4-Wire GFCI Breaker in a 3-Φ, 120/208/240V (High Leg Delta) Panel

The following wiring diagram shows a 80A, 3-pole, 3-phase GFCI breaker with Neutral used in 120/208/240V (High Leg Delta) panel to protect a 240V three-phase load circuit.

In a 120/240V system, the neutral pigtail wire must still be connected to panel neutral busbar. If not required, load neutral does not have to be connected on a 240V circuit.

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A High-Leg Delta (120/208/240V, 3-Phase 4-Wire) system offers:

L1 to L2 = 240V – 1-Phase
L2 to L3 = 240V – 1-Phase
L1 to L3 = 240V – 1-Phase
L1 or L3 to Neutral = 120V – 1-Phase
L1, L2 & L3 = 240V – Three-Phase
L2 (High Leg) to Neutral ≈ 208V – 1-Phase

The color codes used for hot conductors in 120/208/240V high leg delta are as follows:

L1 = Black
L2 = Orange (High or Wild Leg)
L3 = Blue
Neutral = White / Grey
Ground = Bare or Green/ with yellow stripe

In addition, the following wiring configuration illustrates the connection of a NEMA 15-60 receptacle rated for three-phase, 120/208/240V operation. The receptacle is supplied through a three-pole GFCI circuit breaker, with no neutral conductor, as shown below.

Good to Know:

Wiring a three-pole breaker in a High-Leg Delta (120/208/240V) panel requires careful attention because of the high leg (wild leg), which carries a higher voltage (208V to neutral).
Do not use L2 (High Leg or Power Leg) for 120V circuits because power leg to neutral measure 208V – single phase)
High leg marking must be clear. The high leg (L2) must be orange and placed on the center phase in the panel per NEC 110.15 and 408.3(E).

Instructions, Precautions & Codes

The suitable wire size for phase conductors is determined using NEC Table – 310.16.
The equipment grounding conductor (EGC) is sized based on NEC Table 250.122.
The breaker rating and size must match or exceed calculated load or receptacles per NEC Article 210.21(B)(2) & 430 (if motor circuits).
With a 3-pole breaker/GFCI, the appropriate cable types include THHN/THWN-2 (Copper, Aluminum or Copper-Clad Aluminum). Use THHN/THWN-2 for indoor (conduit), THWN-2 or XHHW-2 for outdoor or wet locations, or SOOW flexible cord (indoor/outdoor), Type SER or MC cable for feeder cable and Type UF-B or USE-2 for underground feeder.

Warning:

Make sure to disconnect the power supply by switching OFF the breaker in the main panel before doing any electrical work.
If you are unsure, contact a licensed electrician to do it according to the local area codes.
The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in wrong format. So please! Be careful because electricity is too dangerous.