Home > Electrical Wiring > How to Wire a 3-Phase, 3-Pole Breaker in a Three-Phase Panel

Electrical Design Electrical Wiring How To Protection

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

0 9 minutes read

How to Install a 3-Pole, Three-Phase Breaker in a 120/208Y & 120V/208V/240V High Leg Delta Load Center

A three-pole (3-pole) breaker is a type of circuit breaker designed to simultaneously protect and disconnect three live (hot) conductors in a 3-Φ circuit. It contains three internally linked switches, which trip together if any phase experiences an overload, short circuit, or fault.

A 3P breaker is basically a single unit of three connected circuit breakers with a common internal trip mechanism. The internal trip is mechanically and electrically bonded together and simultaneously disconnects all three hot conductors if a fault occurs on any single phase to protect three-phase electrical systems.

Three-pole breakers are used in three-phase panels and load centers for commercial and industrial applications, such as large three-phase motors, machinery and control panels, welders, pumps and compressors, specific HVAC systems and 3-phase outlets and receptacles.

In other words, three-pole breakers cannot be used in 120V/240V residential applications. This is because 120V/240V panels only provide 120V (line to neutral) and 240V (L1 to L2), making it impossible to install a three-pole breaker in a panel with only two hot legs. Moreover, there is no need to do so, as single-pole and double-pole breakers are sufficient for small-load appliances.

Characteristics:

Number of Poles: 3 – Poles – Connect each phase (L1, L2, L3) to one pole of the breaker.
Voltage: Operates and protects 208V, 240V, 480V, or 600V Three-phase supply (depending on the system). (Three Phases i.e. L1 L2, and L3).
Amperage Rating: 10A to 6000A – Based on NEC Table 240.6(A)
Wiring: 3 hot conductors from the breaker + 1 ground wire (+ 1 neutral (if required) from the ground/neutral busbar connect to the three-phase branch circuit.
Operation: Trips when there is an overload, short circuit, or fault even on a single hot (or phase) wire(s) and trips the breaker to disconnect all hot conductors.
Application: 3-phase loads such as motors, welders, air compressors, and heavy industrial equipment.

Table of Contents

Wiring a Three-Pole Breaker

In the following example wiring diagram, we have wired a 3-phase outlet (NEMA 15-60) protected by a 3-pole, 60A – 250V 3-phase breaker in a 120V/208V/240V high leg delta panel.

Good to Know:

A High-Leg Delta (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

Warning (⚠️ Do not use L2 (High Leg) for 120V circuits because power leg to neutral measure 208V – single phase)

In such a panel:

Single-Pole breakers supply single phase 120V loads (L1 – N or L3 – N).
Single-Pole breakers supply single-phase 120 V loads (L2 (High Leg – N ).
Double-Pole breakers supply 240V single-phase loads (L1 – L2, L2 – L3, or L1 – L3).
Three-Pole breakers supply 240V three-phase loads (L1 – L2 – L3).

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).

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).

To wire a 3-pole breaker in a high leg-leg delta panel, follow the following simple steps:

Before wiring, identify the Terminals as follow:

Line Side (Top): Connects to incoming 3-phase supply (A, B, C).
Load Side (Bottom): Connects to the outgoing 3-phase load.

Wiring Steps:

Turn OFF the main breaker and verify no power using a multimeter.
In the High-Leg Delta panel, locate the three-phase bus bars:
- Left Bus = A-phase (120V to neutral)
- Center Bus = B-phase (High leg, 208V to Neutral)
- Right Bus = C-phase (120V to neutral)
Snap the 3-pole breaker into place so that it connects across all three bus bars (A, B, and C).
Connect the load conductors (from NEMA 15-60 receptacle) to the breaker terminals:
- Load 1 → Phase A terminal – Black Color
- Load 2 → Phase B terminal (High leg) – Orange Color
- Load 3 → Phase C terminal – Blue Color
Connect the equipment grounding conductor (EGC) to the panel ground bus.
If the load needs a Neutral (for control circuit or 120V component), connect the neutral wire from the panel neutral bus (not used in our case i.e. for NEMA 15-60).

Click image or open in a new tab to enlarge

To wire a 3-phase outlet such as NEMA 15-60 to the 3-pole breaker load side terminals, follow the following steps:

Connects Phase A (Black) to the X Terminal of outlet
Connect Phase B (Orange) to the Y Terminal of outlet.
Connect Phase C (Blue) to the Z Terminal of outlet.
Connect Ground (Green / Bare) to the G Terminal of outlet.

Since NEMA 15 series is a 3-pole, 4-wire grounding & without neutral, hence, no load neutral is required.

Similarly, the following wiring diagram shows the connection of a NEMA 18-60 receptacle via 3-pole breaker both rated for 120/208Y – three-phase supply. The non-grounding receptacle is supplied through a 3-pole circuit breaker with neutral and no EGC, as shown below.

Click image or open in a new tab to enlarge

In the example load shown in the fig, we have used to control and wire 60A – (240V and 208Y/120V) receptacles (NEMA 15-60 and NEMA 18-60) with the help of 3-P breaker rated for 60A – 240V and 120/208V Y. For this circuit, we have used #6 AWG copper (THHN) or #4 AWG aluminum (based on 60A and 75 °C rating per NEC Table 310.16, which is the suitable conductor size for 60A circuit and the associated NEMA 15-60R and 18-60R. In addition, use 10 AWG for equipment ground conductor (EGC) per NEC Table 250.122 for a 60A grounding circuits.

Wiring 3-Pole GFCI Breakers

Wiring a 3-pole GFCI breaker is similar to wiring a standard 3-pole breaker, except for the white (built-in pigtail) wire. This pigtail must be connected to the neutral busbar in the main service panel.

In most three-phase circuits, a neutral wire is not required. However, if the circuit does require a neutral, connect the neutral wire from the GFCI breaker directly to the load instead of the neutral busbar. If a neutral connection is not available from the GFCI load terminal, connect it from the neutral busbar to the load point.

The following wiring diagram shows a 20A, 208V, 3-pole, 3-phase GFCI breaker used to protect a 208V three-phase appliance.

Click image or open in a new tab to enlarge

Instructions, Precautions & Codes

The suitable wire size is 6 AWG copper (or #4 AWG aluminum) to use with a 60A outlet and circuit breaker – NEC Table – 310.16, Table – 210.24(1) and NEC 240.4(D)(4). Therefore, use #12/3 cable (three hot wires and one ground (and one neutral if required) for a 60A-240V 3-P breaker and associated load circuits.
For a 60A circuit , the equipment grounding conductor (EGC) can be #10 AWG copper. NEC Table 250.122.
The correct size of breaker is 3-pole, 60A circuit breaker or GFCI for a 60A-240V three-phase outlet – NEC 210.21(B)(2).
With a 3-pole, 60A breaker, 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.
A three-pole 60A breaker can be used for 48A continuous load (which lasts 3 or more hours) and maximum 60A non-continuous load – 210.19(A), 210.20(A), 215.2(A), 215.3, and 230.42(A).
A 3-pole, 60-amp breaker at 240 volt can handle non-continuous load of 14,400 watts (60A × 240V). For continuous use, limit the load to about 11,520 watts (80% of 14,400W).

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.

Resources:

Standard Breakers & GFCI Breakers Wiring Installations

How to Wire a 1-Pole Breaker
How to Wire a 2-Pole Breaker
How to Wire a 3-Phase, 3-Pole Breaker … You Are Here
How to Wire a Tandem Breaker
How to Wire a 1-Pole GFCI
How to Wire a 2-Pole GFCI
How to Wire a 3-Phase, 3-Pole GFCI Breaker
How to Wire GFCI Circuit Breakers
How to Wire an AFCI Breaker

Sizing Breakers, Wires, and Panels

General Outlets and GFCI/AFCI Receptacles Wiring

Switches Wiring

Finding the Number of Breakers/Outlets in a Circuit

Main Panels Wiring Tutorials

General Wiring Installation Tutorials:

Related Posts:

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