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How to Wire a 30A, 125V/250V – NEMA 14-30 Receptacle

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How to Install a 30A – 125/250V Grounding Receptacle with Neutral – Wiring NEMA 14-30 with Breaker & GFCI Protection for Heavy-Duty EV Chargers, RVs, Electric Ranges & Dryers

A NEMA 14-30R is a common type of receptacle (outlet) found in homes and industrial equipment. They are most often used to power clothes dryers, electric ranges, welders, cooktops, compressors, generators and Level 2 electric vehicle (EV) charging.

NEMA 14-30 is a 3P, 4W receptacle which is capable to handle 30-amps at 125/250 volts of single phase power supply. The industrial grade 30-amp receptacle is suitable for high-wattage residential equipment and charging electric vehicles (EVs) which runs for hours.

In the following wiring tutorial, we will demonstrate how to wire a NEMA 14-30 receptacle using both standard and GFCI breakers. The wring diagrams also shows the correct breaker and wire size used with 30-amp receptacle for high-wattage appliances and charging EVs.

Table of Contents

The NEMA 14-30 Receptacle

The NEMA 14-30R is a 125/250V receptacle with grounded neutral used with 14-30P plug. As the name suggests, the “30” in the 14-30R indicates the maximum amperes of current, while the “R” stands for “Receptacle (outlet). Similarly, the “P” in the NEMA-14-30P indicates “Plug”, with “30” denoting the maximum current in amperes.

NEMA 14-30 comes in a 3-pole, 4-wire configuration which means it requires a neutral wire. It has two hot slots (prongs) for Hot 1 and Hot 2, a neutral slot (in shape of half “T”, and a grounding slot for EGC.

Terminals

There are four terminals in a 14-30R receptacle in accordance with UL 498 and CSA:

G terminal (green screw): For equipment grounding conductor (EGC) – Bare or Green wire.
X terminal (brass screw): For HOT 1 (Line 1) – Black Wire
Y terminal (brass screw): For HOT 2 (Line 2) – Red Wire
W (silver screw): For Neutral wire (grounded conductor) – White or Grey wire.

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Electrical Ratings & Specifications

NEMA: NEMA 14-30R – Straight-Blade Receptacle
Poles: 3-Poles, 4 Wires – Grounding with Neutral
Wires: Four Wires – Hot 1, Hot 2, Neutral and Ground
Voltage: 125V – 250V Single-Phase AC Supply – 60 Hz
Breaker / GFCI: 30A
Current: 24A – 30A
Wattage: 7,200 W
Wire Size: #10 AWG (Copper Only)
Temp. Rating: -40°C to 75°C (-40°F to 167°F)
Dielectric-strength: Withstand 2kV
Grade & Material: Industrial Grade & Weather-resistant (WR) with Reinforced Thermoplastic Polyester
Mounting: Flush / Screw Mounting
Outdoor Box: 2-gang outdoor box – NEMA 3R rainproof enclosure
Wiring: Hardwired / Dedicated Circuit

Good to Know:

For EV charging, It is advisable to use Industrial grade and EV Rated outlet instead of standard outlets and receptacles. This is because the standard 30A receptacle can be used for maximum 24A of continuous load as per NEC 80% continuous load rule while the industrial grade can be used for 30A continuous load for extended periods (e.g. EV charging) without overheating or deteriorating.
The EV Rated 30A, NEMA 14-30 has a “Green vehicle” icon on the front side as shown in the fig.

Wiring NEMA 14-30R Receptacle with a GFCI

A NEMA 14-30 receptacle for electric vehicle (EV) charging can be either plug-in or hardwired. The 30-amp outlet must be protected by a 30A GFCI breaker if ground-fault protection is not already built into the EV charger.

As shown in the wiring diagram:

Connect the two hot wires (Hot 1 – black and Hot 2 – red) from the 2-pole, 30A GFCI breaker to the X and Y terminals of the NEMA 14-30 receptacle.
Connect the neutral wire (white) to the W terminal.
Connect the ground wire (bare copper or green with yellow stripe) to the G terminal.
For proper operation, ensure the built-in white pigtail wire from the GFCI breaker is connected to the neutral busbar in the 120/240V main panel.

Although the NEMA 14-30 receptacle can accept wire sizes from #12 AWG to #6 AWG, the recommended conductors for this application are #10 AWG or #8 AWG, depending on the load and installation conditions.

For outdoor installations, use a NEMA 3R weatherproof (rainproof) 2-gang enclosure to provide adequate protection against moisture and environmental exposure.

Good to Know:

NEC Article 625.54 specifies that receptacles installed for the connection of Electric Vehicle Supply Equipment (EVSE) must be provided with ground-fault circuit interrupter (GFCI) protection for personnel.
According to NEC – 210.8(A)(1) through (A)(11), an outdoor receptacle must be installed downstream of a GFCI breaker, in accordance with Articles 426.28 or 427.22.
As per NEC – 625.41 for electric vehicle branch circuit, each electric vehicle charging outlet must be supplied by a dedicated branch circuit with no other outlets connected.
Nuisance tripping may occur if both the EV charger and the receptacle are GFCI protected.

The following wiring diagram shows how to install a NEMA 14-30R, 30-amp industrial grade receptacle using a 2-pole, 30A GFCI breaker.

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Good to Know:

Tighten terminal screws to approximately 75 lb.-in (8.5 N·m) using a 3/16″ Allen wrench.
Strip each conductor 11/16″ or refer to the stripe gage on mounting plate.

Wiring NEMA 14-30 Receptacle with Breaker

The wiring configuration of a NEMA 14-30 receptacle with a 30A, 2-pole standard breaker is the same as when using a 2-pole GFCI breaker.

A standard breaker is often preferred for this installation because it helps prevent nuisance tripping, especially when the EV charger or appliance already includes built-in GFCI protection (as most modern EV chargers do).

The following wiring diagram illustrates how to connect a NEMA 14-30, 30-amp receptacle using a 2-pole, 30A standard breaker for RVs, induction ranges, EV charging, or other high-wattage devices.

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FAQs:

Should I Use a GFCI or Standard Breaker with NEMA 14-30 Receptacle ?

You should use a standard 2-pole 30A breaker unless your local electrical code requires GFCI protection. Many EV chargers already have built-in GFCI protection, and double protection can cause nuisance tripping. If GFCI is required by NEC (e.g., in garages or outdoors), use a 2-pole 30A GFCI breaker.

For instance, If you are in a state which adopted the NEC – 2020 or 2023, you have the following options:

Install a GFCI prior the NEMA 14-30 receptacle to work with the mobile connector and plug adapters.
Replace the existing socket outlet with a disconnect switch and hard wire the Electric Vehicle Supply Equipment “EVSE”.

Good to Know: NEC – 210.8(A)(1) through (A)(11) and 625.54 in accordance with Articles 426.28 & 427.22 required outdoor receptacles and outlets used for EV charging must be GFCI protected.

How Many Amps Can NEMA 14-30 Receptacle Handle Safely?

A NEMA 14-30 receptacle is rated for 30 amps maximum. For continuous loads (3+ hours, such as EV charging), NEC requires derating to 80% of breaker rating (also known as 125% rule) specified in 210.19(A)(1) and 210.20(A), so it can handle up to 24 amps continuously.

Continues Load: 30A × 80% = 24-Amp
Non-continuous Load: 30-Amp

In the case of an industrial-grade 30-amp receptacle, it is designed to safely handle a continuous load of 30 amps for extended periods of time.

These ratings comply with NEC Sections 210.19(A)(1), 215.2, and 230.42(A) for continuous and non-continuous loads, and 110.14(C) for ambient temperature.

Which Breaker Size is Suitable for NEMA 14-30 Receptacle ?

For continuous load, we will use the 80% rule (which shows only 80% of the load should be connected to the rated circuit breaker). In addition, the size of the OCPD (fuse or circuit breaker) should handle 125% of the load circuit.

Continues Load of 24A × 125% = 30-Amp
Non-continuous Load = 30-Amp

NEC Table 210.21(B)(3) shows 30-amp receptacle can be used to service 30-amp load circuit. Therefore, based on NEC 210.19(A)(1) and 210.20(A), the correct breaker size for 30-amp outlet (NEMA 14-30) is a 2-pole 30A breaker or GFCI at 240V.

How Many Watts Can a 30A, 14-30 Receptacle Hold?

At 240V, a 30A receptacle can supply:

Maximum: 30A × 240V = 7,200 watts
Continuous load (80% rule): 24A × 240V = 5,760 Watts

What is the Correct Wire Size and Cable Type to Use with NEMA 14-30?

As mentioned before, the 30-amp receptacle can be used for 24A continuous and 30A non-continuous load, (industrial grade can be used for 30-amp continuous).

For this ampacity, the #10 AWG copper can carry 30A at 60°C (140°F), 35A at 75°C (167°F) and 40A at 90°C (194°F) which is suitable wire size for NEMA 14-30 receptacle according to NEC Table 310.16) and CEC Table 2.

To be on the very safe side, you may use #8 AWG copper with a 30-amp, NEMA 14-30 receptacle (outlet).

Similarly, for a circuit of up to 30-amp protected by OCPDs, ground wire (EGC) can be #10 AWG as per NEC Table 250.122.

For indoor, dry locations (Romex / NM-B): Use #10/3 NM-B copper cable with ground
In Conduit Installations (Basement, Garage, Commercial): Use individual THHN/THWN-2 copper conductors, 10 AWG, in conduit (PVC, EMT, or flex)
In Outdoor or Underground (Wet Locations): Use UF-B cable (#10/3 with ground) rated for direct burial or THWN-2 conductors in conduit
EGC (Ground Wire): Min #10 AWG
Always follow NEC ampacity tables and adjust for distance, ambient temperature, or conduit fill.

Can I Use NEMA 14-30 Outlet on a 40/50A Breaker?

A NEMA 14-30 receptacle must be protected by a 30A breaker when the intended continuous/non-continuous load is up to 30A.

While 14-50 on a 30A breaker is code-compliant and technically possible, but it will cause issues with many plug-in chargers. In this case, using a NEMA 14-30 on 40/50A breakers is generally not the best idea. For maximum safety and reliability, it is better to install a hardwired EV charger instead of relying on a plug-and-outlet connection.

Can You Install NEMA 14-30R in 120V AC Circuit?

No, a NEMA 14-30 is designed for 240V, 4-wire circuits (2 hots, 1 neutral, 1 ground). This configuration is not feasible in single phase 120V supply (1 Hot + Neutral + Ground).

If 30-amp in a 120V single-phase supply is required for RVs, a NEMA TT-30 receptacle may be used instead.

Instructions, Precautions & Codes

If your main purpose for installing the 14-30R receptacle is for EV charging, use an industrial-grade, EV rated device.
It is recommended to hardwire instead of plug-in a 30-amp receptacle especially for EV charging.
Install the 14-30R near the vehicle charging port, a maximum of 15 feet (4.5 meters) away.
The recommended height of the outlet is 4 ft (1.2 meters) above the floor.
If the installation location is near the main panel and you want to install it in the lower portion, a minimum height of 18 inches (45 cm) above the ground is suitable.
The 14-30R should not be used with single-gang wall boxes. Use a 2-gang outdoor box and NEMA 3R rainproof enclosure, especially for outdoor applications.
According to the NEC Table – 310.16 and 210.24.(1), the correct Breaker and Wire size for a 30-Amp, 14-30 receptacle is #10 AWG copper.
Use #10-3 wires (including 2-hot, 1 neutral and 1 ground) for 240V, 30-Amp breaker and outlet/receptacle.
Longer runs (when the distance is more than 50 ft (15.25 meters) require an upgrade and larger wire gauge size to compensate for voltage drop.
A standard 30-amp receptacle can be used for a 24-amp continuous load and a maximum 30-amp non-continuous load (210.19(A)), 215.2, and 230.42(A). However, the industrial grade can be used for 30-amp continuous load.
It is against the code to use a 30-amp receptacle to draw 30-amp on a 20/25-amp breaker.
It is against the code to use smaller gauge wire sizes (e.g., using 12, 14 AWG) instead of 10 AWG wire with a 30-amp breaker and outlet.
According to the NEC – 310.16, add 20% of additional ampacity for every 100 feet (30.50 meters) of distance (for example between main panel and subpanel) to counter the voltage drop. For distance and ambient temperature rating (Refer to 110.14(C), 310.15(B)(2)), 310.16 and 240.4(A).
30A, 240V outlet can be installed on 30 amp breaker/GFCI only.
30A, 240V outlet can only be used as dedicated circuit for single unit especially for EV charging – NEC – 625.41.

Warning

Always disconnect the power supply by switching OFF the breaker in the main service panel before performing any electrical work.
If you are not confident or qualified, consult a licensed electrician to ensure the installation is performed safely and in compliance with local electrical codes.
The author assumes no responsibility for any losses, injuries, or damages resulting from the use or misuse of the information provided. Electricity is extremely dangerous! please exercise caution and never attempt wiring unless you fully understand the process.

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