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How to Wire a Two-Pole Circuit Breaker in a 120/240V Panel

Electrical Technology
0 9 minutes read

How to Install a Standard 2-P, 20A – 240V Breaker for Branch Circuits

Two-Pole Breakers:

A Two-pole breaker (also known as double-pole or 2-pole breaker) is a type of circuit breaker that connects to both hot wires (phase conductors) in a 240-volt circuit. It provides simultaneous protection for both conductors, meaning if an overload or short circuit occurs on either leg, both poles trip together, and shut-off the power to the entire circuit.

A double-pole breaker is essentially two single-pole breakers combined into one unit and occupies two slots in a breaker panel. It is commonly used in both residential and commercial applications for small to heavy-duty load appliances and equipment that need both hot legs for full voltage operation.

In residential applications, double-pole breakers (typically rated 15A to 60A) are used for 240V air-conditioners, water heaters, compressor, pumps, subpanel, EV charging and general-purpose outlets and receptacles. In commercial applications, double-pole breakers with ratings ranging from 15A up to 100A+ are used for heavier-duty circuits, such as HVAC, commercial kitchen appliances, industrial machinery, heavy-duty utility loads, subpanels and main switches, multi-wire branch circuits and specialized outlets.

Characteristics:

  • Number of Poles: 2 poles for hot terminals (mechanically and electrically linked) which connects to both lines (L1 & L2) i.e. hot wires (red and black in the US followed by NEC).
  • Voltage: Operates on and protects 240V branch circuits. (Two phases i.e. L1 and L2).
  • Amperage Rating: Mostly used in 15A to 100A+. Standard Rating in NEC Table 240.6(A) is 10A – 6kA.
  • Wiring: 2 hot wires from the breaker + 1 ground wire (+ 1 shared neutral (if required) from ground/neutral busbar connect to the branch circuit in a 240V supply.
  • Operation: Trips when there is an overload, short circuit, or fault on the single or both hot (or phase) wire(s).
  • Application: Used for standard lighting, outlets, receptacles, sockets and small to medium load appliances.

Wiring a Double-Pole Breaker

1. Before working inside the panel, switch off the main breaker to cut power to all branch circuits. Verify there’s no voltage using a non-contact voltage tester.

2. Identify the cable in 120V/240V main panel. For a 240V-only circuit, use 2-conductor cable with ground i.e.

  • Black wire (Hot 1)
  • Red wire (Hot 2)
  • Bare/green wire (Ground)

3. Strip about ½ inch (≈12 mm) of insulation from both hot wires (black & red). Expose the ground wire for connection to the grounding bar. If using a neutral wire (white), strip it and connect it to the neutral bar.

4. Connect the Hot Wires to the Breaker:

  • Insert the black wire into one terminal of the double-pole breaker.
  • Insert the red wire into the other terminal.

Tighten both screws securely. These two wires will carry 120V each from opposite phases, totaling 240V between them.

5. Connect the Ground (and Neutral if applicable). Attach the bare/green wire to the grounding bar in the panel. If the circuit or appliance requires a neutral, connect the white wire to the neutral bar

6. Install the breaker into the panel. Align the breaker’s clips with the bus bars in the panel. Firmly press the breaker into place, so it should snap onto both bus bars (L1 & L2) to provide 240V.

7. Label the Breaker i.e. mark the breaker’s panel slot with a clear description, e.g., “Water Heater – 240V, 20A”.

8. Restore power and test. To do that, turn the main breaker back ON. Switch ON the new double-pole breaker. Test voltage at the appliance receptacle or connection:

  • Between Hot 1 and Hot 2: ≈ 240V
  • Between Hot 1 or Hot 2 and Ground: ≈ 120V each

How to Wire a Two-Pole Breaker in 120-240V Panel

In the example load shown in the fig, we have used to control and wire 20A – 240V receptacle (NEMA 6-20) with the help of 2-P breaker rated for 20A – 240V. For this circuit, we have used #12 AWG copper wire (Based on NEC Table 310.16), which is the correct size for a 20A circuit and the associated NEMA 5-15R outlet. In addition, Similar wire size i.e. 12AWG should be used for equipment ground conductor (EGC) per NEC Table 250.122.

Good to Know:

As we know that 2-pole breakers are used for standard 240V circuits, therefore, two-pole breakers cannot be used in place of 1-pole breakers, which are designed for 120V circuits where only one pole (i.e., 1 hot wire either L1 or L2) are wired, control and protected.

Expect the 20A outlet, the double pole breaker can be wired for different ratings and NEMA outlets used in 240V supply systems such as.

Wiring 2-Pole GFCI Breakers

Wiring a 2-pole GFCI breaker is similar to wiring a standard 2-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 240V circuits, a neutral wire is not required. However, if the circuit does require a neutral, connect the neutral wire from the GFCI load side directly to the load instead of wiring it to the neutral busbar.

The following wiring diagram illustrates a 20A, 240V standard outlet protected by a 2-pole GFCI breaker rated for 20A at 240V.

How to Wire a Two-Pole Breaker in 120-240V Panel

Similarly, the given wiring diagrams shows the installation of 2-Pole GFI breakers with neutral and without neutral for 20A to 50A outlets etc. In addition, the wiring diagrams shows the installation of 2-Pole breakers with 15A, 20A and 30A GFCI outlets.

Instructions, Precautions & Codes

  • The suitable wire size is 12 AWG copper (or #10 AWG aluminum) to use with a 20A outlet and circuit breaker – NEC Table – 310.16, Table – 210.24(1) and NEC 240.4(D)(4). Therefore, use #12/2 cable (two hot wires and one ground (and one neutral if required) for a 20A-240V breaker and associated load circuits.
  • For a 20A circuit , the equipment grounding conductor (EGC) can be #12 AWG copper. NEC Table 250.122.
  • The correct size of breaker is 2-pole, 20A circuit breaker or GFCI for a 20A-240V outlet – NEC 210.21(B)(2).
  • With a 2-pole, 20A breaker, the appropriate cable types include NM-B (Non-Metallic Sheathed Cable) for indoor/dry locations, THHN / THWN-2 for conduit wiring (indoor/outdoor or wet locations), UF-B for outdoor or underground wiring, SOOW or SJTW (Flexible Cord) for industrial or flexible wiring.
  • A double-pole 20A breaker can be used for 16A continuous load (which lasts 3 or more hours) and maximum 20A non-continuous load – 210.19(A), 210.20(A), 215.2(A), 215.3, and 230.42(A).
  • A 2-pole, 20-amp breaker at 240 volt can handle non-continuous load of 4,800 watts (20A × 240V). For continuous use, limit the load to about 3,840 watts (80% of 4,800W).
  • If more than one receptacle on the same circuit, you may allowed to use 15A outlet on 20A circuit breaker, otherwise, do not use 20A outlet on 15A circuit breaker. In short, It is code to use 15A outlet on 20A breaker (NEC 210.21(B)(2)), but it is not allowed to use 20A outlet on 15A breaker.

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

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:

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0 9 minutes read

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