How to Wire a 20A, 125V/250V – NEMA 14-20 Receptacle

Electrical Technology

How to Install a 20A – 125/250V Grounding Receptacle with Neutral – Wiring NEMA 14-20 with 2-P Breaker & GFCI Protection

A NEMA 14-20 receptacle is a 3P, 4W, 20A, 125/250V grounding receptacle designed for applications that require separate neutral, ground and two hot wires. It is part of the NEMA 14 series, which includes modern grounding-type configurations for medium-duty circuits.

While the NEMA 14-20R receptacle is not very common in use, it is still available from various manufacturers such as Hubbell, Leviton, and Legrand. The following wiring guide provides an overview of its application in case you encounter a situation that requires a 4-wire setup for 20-amp circuits.

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The NEMA 14-20 Receptacles

A NEMA 14-20 receptacle is a 20A, 125/250V, 3-pole, 4-wire receptacle used for connecting medium-power equipment like portable generators and certain large appliances. The “14” indicates it’s a 4-wire, single-phase receptacle, the “20” is for 20 amps, and the “125/250V” is the voltage rating. Its locking versions i.e. L14-20 (R & P) are designed for a secure, “locking” connection that prevents accidental unplugging.

The NEMA 14-20R receptacle features two vertical slots (X and Y) for the hot wires (Hot 1 and Hot 2), one horizontal slot for the neutral wire, and a U-shaped slot for the ground pin. Do not confuse it with NEMA 14-60 having neutral, or older NEMA 10-20 or NEMA 6-20 types, which lack a dedicated neutral or ground.

Warning: NEMA 14-20 and NEMA 14-60 receptacles have almost identical slot configurations. Be careful not to confuse them when plugging in 14-20P or 14-60P plugs. Always verify nameplate marking of the current and voltage rating on the outlet before use.

While not very common in residential use, the NEMA 14-20 is used in specialized equipment setups that need both 120V and 240V circuits, under 20 amps. For instance, dual voltage ovens & laundry units, commercial and industrial lighting equipment, power distribution panels, generators, electric ranges or welders, RVs, campers, and trailers.

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Terminals

There are three terminals in a 14-20R receptacle.

Hot 1 (L1): Black Wire → Right Side Brass Screw – Vertical Slot (I)
Hot 2 (L2): Red Wire → Left Side Brass Screw – Vertical Slot (I)
Neutral (N): White Wire → Silver Screw – Horizontal Slot (➖)
Ground (G) for EGC (⏚): Green or Bare wire → Green Screw – (U) Shaped Terminal.

Electrical Ratings & Specifications

NEMA: NEMA 14-20R – Straight-Blade Receptacle
Poles: 3-Poles, 4 Wires – Grounding with Neutral
Wires: Four Wires – 2-hot i.e. (Hot 1 & Hot 2), 1 Neutral and 1 Ground
Voltage: 125V – 250V Single-Phase AC Supply – 60 Hz
Breaker / GFCI: 20A
Current: 20A – 16A
Wattage: 4,800 W
Wire Size: #12AWG Copper
Temp. Rating: -40°C to 75°C (-40°F to 167°F)
Grade & Material: Industrial Grade – Phenolic & Nylon, PBT – with Nickel Plated Steel
Termination: Back & Side Wired
Mounting: Flush / Screw Mounting
Wiring: Hardwired / Dedicated Circuit

Wiring NEMA 14-20R Receptacle

Wiring 20A – 120V/250V Receptacle using 2-P Breaker

The following wiring diagram illustrates the wiring connections of a 20A, 125V/250V receptacle (NEMA 14-20R) to a two-pole, 240V – 20A circuit breaker in a 120/240V main panel.

Wiring Instructions for NEMA 14-20R receptacle:

Strip the Insulation: Remove about 3/4 inch (19 mm or 1.9 cm) of insulation from the side wire, and about 1/2 inch (12.7 mm or 1.27 cm) from the back wire.
Connect the ground wire: Attach the bare or green wire to the green screw, which is the centered, round, or U-shaped “G” terminal.
Connect Neutral (White): Secure the white wire to the silver screw on the lower horizontal slot (W) terminal.
Connect Hot 1 (Black): Secure the black wire to the brass screw on the left vertical slot (X) terminal.
Connect Hot 2 (Red): Secure the red wire to the brass screw on the right vertical slot (Y) terminal.
Tighten all terminal screws: Torque each screw to approximately 14-18 lb-in (1.6-2 N·m) to ensure a solid electrical connection.

For this installation, use #12 AWG copper wire, which is the correct conductor size for a 20A circuit and compatible with the NEMA 14-20R receptacle.

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Wiring 20A – 120V/250V Receptacle with GFCI

According to NEC 210.8, GFCI protection is required for receptacles installed in garages, basements, outdoor areas, laundry spaces, and other wet or damp locations. Specifically, NEC 210.8(A)(1) through (A)(11) mandates that all outdoor receptacles must be installed downstream of GFCI protection, in accordance with Articles 426.28 and 427.22.

Currently, only 15A and 20A GFCI receptacles rated for 120V are available, typically in NEMA 5-15 and NEMA 5-20 configurations. For 125V/250V circuits, GFCI protection must be provided using two-pole (2-P) GFCI circuit breakers, as 240V GFCI receptacles are not yet available.

To install a 20A, 120V/250V receptacle in any location where GFCI protection is required by code, simply replace the standard two-pole 20A breaker with a two-pole, 20A GFCI circuit breaker (240V rated). Be sure to connect the built-in white pigtail lead from the GFCI breaker to the neutral bus bar in the main panel. The rest of the wiring remains unchanged, as illustrated in the following wiring diagram.

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FAQs:

How Many Amps Can a NEMA 14-20 Receptacle Handle Safely?

A 20A – 125/250V receptacle is rated to safely handle up to 20 amperes of current continuously. However, per NEC Articles 210.19(A), 210.20(A), 215.2(A), 215.3, and 230.42(A), the continuous load should not exceed 80% of the outlet’s rating, which equals 16 amps for long-duration use (3 hours or more).

How Many Watts Can a 20A – 125/250V Receptacle Hold?

The maximum wattage depends on the operating voltage:

At 120V, the receptacle can supply up to 2,400 watts (120V × 20A).
At 240V, it can supply up to 4,800 watts (240V × 20A).

For continuous loads, use only 80% of these values – 1,920W at 120V and 3,840W at 240V.

Which Breaker Size is Suitable for a NEMA 14-20 Receptacle?

The correct breaker size is 20A – 240V, 2-pole circuit breaker or GFCI for a 20A – 125/250V receptacle . The double-pole breaker ensures both hot legs are simultaneously disconnected during faults or maintenance.

What is the Correct Wire Size and Cable Type to Use with NEMA 14-20 Receptacle?

Based on NEC Table 310.16, Table 210.24(1), and NEC 240.4(D)(6), the minimum recommended wire size is 12 AWG copper for a 20A receptacle. Similarly, the size of equipment grounding conductor (EGC) can be #12 AWG as per NEC Table 250.122 to protect the 20A circuit (Breaker, Outlet & Connected Load).

Suitable cable types include:

NM-B (Romex) for fixed indoor residential use.
UF-B for underground or outdoor applications.
SOOW/SJTW for flexible cord applications
THHN/THWN conductors in conduit for commercial or exposed installations.

Can You Install a NEMA 14-20R in a 120V AC Circuit?

No. The NEMA 14-20R is a 4-wire, 120/240V receptacle that requires two hot wires, one neutral, and one ground. Installing it on a single-phase 120V circuit would result in improper wiring and unsafe operation. Always connect NEMA 14-20R to a 120/240V split-phase circuit using a two-pole 20A breaker as required by NEC 210.21(B).

Can You Plug a NEMA 14-20 Plug into a NEMA 14-60 Receptacle?

No. Although NEMA 14-20 and NEMA 14-60 look similar, their current ratings (20A vs. 60A) are different, and their plug blades are sized differently to prevent interconnection. For safety and NEC compliance, always match the plug and receptacle type and rating exactly.

Warning

Always turn off the power supply by switching OFF the circuit breaker in the main electrical panel before performing any electrical work.
If you are unsure or inexperienced, it is strongly recommended to contact a licensed electrician to perform the work in accordance with local electrical codes and safety regulations.
The author assumes no responsibility or liability for any losses, injuries, or damages resulting from the use, misuse, or improper application of the information provided. Please be safe because playing with electricity is extremely dangerous.

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