How to Wire NEMA TT-30 Receptacle for RVs & Travel Trailers

Electrical Technology

How to Install a NEMA TT-30 Receptacle (30A/125V) with 1-Pole Breaker and GFCI Protection for RVs & Travel Trailers

A NEMA TT-30R is a 30-amp, 125-volt, 3-pin, grounded receptacle specifically designed for recreational vehicles (RVs), travel trailers, and other applications such as food trucks, campers and portable generator.

The NEMA TT-30 is a 2P, 3W receptacle rated for 30 amps at 125V on a single-phase power supply. It is intended for use on 120V circuits. If you require the same amperage for a 240V circuit, you should use an alternative receptacle such as NEMA 14-30, NEMA 10-30 (with neutral), or NEMA 6-30 (without neutral).

In the following wiring tutorial, we will demonstrate how to properly wire a NEMA TT-30 receptacle using both standard and GFCI breakers. The included wiring diagrams show the correct breaker size and wire gauge for a 30-amp receptacle, making it suitable for travel trailers, RV hookups, and temporary 120V appliances.

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The NEMA TT-30 Receptacle

The NEMA TT-30R is a 2-pole, 3-wire receptacle specifically designed for 125-volt operation. It is a special-purpose receptacle intended for travel trailers and recreational vehicles (RVs). The TT-30R is paired with a TT-30P plug, which features a grounded neutral connection.

The designation “TT” stands for Travel Trailer, highlighting its primary application. The number “30” indicates the maximum current rating of 30 amperes, while the letter “R” denotes that it is a receptacle. Likewise, the “P” in TT-30P refers to the plug with the same 30-amp current rating.

To help with identification and to distinguish it from other NEMA configurations, the TT-30 receptacle and plug feature a unique pin layout: one round pin for ground and two slightly angled flat pins for the hot and neutral conductors.

Because this device is dedicated for RV and travel trailer use, the NEMA TT-30 receptacles are clearly labeled with “Travel Trailer” or “For Recreational Vehicle Use Only.”

Terminals

A NEMA TT-30R receptacle has three terminals as follow:

G Terminal (Green Screw): Equipment Grounding Conductor (EGC) – For bare or green wire.
*Y Terminal (Brass Screw): Hot (Line) Conductor – For the black or red wire.
W Terminal (Silver Screw): Neutral (Grounded Conductor) – For the white wire.

*Warning: The terminals labeled X or Y (brass-colored screws) are always for ungrounded (hot) circuit conductors. Do not connect the line (hot) conductor to the white (neutral) or green (ground) terminals, as doing so can create a shock hazard or damage equipment.

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Electrical Ratings & Specifications

Poles: 2-Poles, 3 Wires
Voltage: 125V – Single-Phase AC Supply – 60 Hz
Breaker / GFCI: 30A
Current: 24A – 30A
Wattage: 3,600 W
Wire Size: #10 – #8 AWG (Copper Only)
Temp. Rating: -20°C to 75°C (-4°F to 167°F)
Dielectric-strength: Twice the device rating + 1kV per UL498
Grade & Material: PVC base with Zinc/galvanized steel plate and steel lugs
Mounting: Flush / Screw Mounting
Outdoor Box: 2-gang outdoor box – NEMA 3R rainproof enclosure
Wiring: Hardwired / Dedicated Circuit

Wiring NEMA TT-30R with a GFCI

A NEMA TT-30 receptacle for recreational vehicles (RVs) can be installed as either a plug-in or hardwired connection.

According to NEC 551.71(F)(1) & (2), GFCI protection is not required for large outlets (30A and 50A) serving RVs or other equipment that is not part of an RV site. However, NEC 210.8(B) requires GFCI protection for outdoor outlets in many applications, so it is generally recommended to install a GFCI-protected breaker, especially for outdoor setups.

Wiring Instructions

As shown in the wiring diagram:

Hot (Line) Connection: Connect the hot wire (black or red) from the 1-pole, 30A GFCI breaker to the Y terminal (brass screw) of the NEMA TT-30 receptacle.
Neutral Connection: Connect the neutral wire (white) to the W terminal (silver screw).
Ground Connection: Connect the ground wire (bare copper or green/yellow) to the G terminal (green screw).
GFCI Breaker Pigtail: Ensure the white pigtail wire from the GFCI breaker is properly connected to the neutral bus bar in the 120/240V main panel to complete the GFCI circuit.

Conductor Size

Although the NEMA TT-30 receptacle can accept wire sizes from #10 AWG to #4 AWG, the recommended conductor size for a 30A circuit is:

#10 AWG copper (standard installation)
#8 AWG copper (long runs or higher ambient temperature conditions)

For outdoor applications, install the receptacle in a NEMA 3R weatherproof (rainproof) 2-gang enclosure to provide proper protection against moisture, dirt, and environmental exposure.

Good to Know:

NEC 551.71(F)(2): In RV parks, all 125V, 15A and 20A receptacles provided for RV sites must have ground-fault circuit interrupter (GFCI) protection.
Larger 30A and 50A receptacles are not required to have GFCI protection, since RVs often produce excessive amounts of leakage current that could lead to nuisance tripping.
NEC 210.8(A)(1) through (A)(11): Outdoor receptacles must still be installed downstream of a GFCI device or breaker in accordance with 426.28 or 427.22.

The following wiring diagram illustrates how to properly install a NEMA TT-30 30A/125V receptacle using a 1-pole, 30A GFCI breaker for RVs.

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Good to Know:

Tighten terminal screws to approximately 25 lb.-in (3.0 N·m) of torque.
Strip each conductor 1/2″ (1.3cm) or refer to the stripe gage on mounting plate.

Wiring NEMA TT-30 Receptacle with Breaker

The wiring configuration for a NEMA TT-30 receptacle with a 1-pole, 30A standard breaker is identical to the configuration used with a 1-pole, 30A GFCI breaker (as shown in the diagrams above and below).

In many RV installations, a standard breaker is often preferred because it helps prevent nuisance tripping. Appliances and onboard systems in recreational vehicles can produce enough amounts of leakage current that may exceed the trip threshold of a Class A GFCI device, which results in unnecessary power interruptions.

The following wiring diagram demonstrates how to connect a NEMA TT-30, 30A-125V receptacle using a 1-pole, 30A standard breaker, suitable for powering RVs, food trucks, portable generators, and other temporary 120V operations.

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FAQs:

Should I Use a GFCI or Standard Breaker with NEMA TT-30 for RVs?

In most RV and campground installations, a standard 1-pole, 30A breaker is recommended unless local electrical codes specifically require GFCI protection. This is because nuisance tripping can occur when using a GFCI breaker. This is because RV appliances often produce small leakage currents that can exceed the trip threshold of a Class A GFCI device.

If GFCI protection is required (for example, in outdoor installations as specified by NEC), use a 1-pole, 30A GFCI breaker to meet NEC requirements.

Good to Know:

NEC 551.71(F)(1) & (2): All 125V, 15A, and 20A receptacles provided for RV sites must have GFCI protection.
NEC 210.8(A)(1) – (A)(11) & 625.54: Outdoor receptacles must be GFCI-protected, in accordance with Articles 426.28 and 427.22.

How Many Amps Can 30A, TT-30 Receptacle Handle Safely?

A NEMA TT-30 receptacle is rated for a maximum of 30 amps. For continuous loads (lasting 3 hours or more), NEC requires derating to 80% of the breaker rating (commonly known as the 125% Rule) as specified in NEC 210.19(A)(1) and 210.20(A).

Continuous Load: 30A × 80% = 24A maximum
Non-Continuous Load: Up to 30A

On the other hand, industrial-grade TT-30 receptacles allow safe operation at the full 30A rating continuously.

These ratings comply with:

NEC 210.19(A)(1), 215.2, 230.42(A): Conductor sizing for continuous and non-continuous loads
NEC 110.14(C): Temperature limitations for terminals and conductors

Which Breaker Size is Suitable for a TT-30 Recpetacle?

For a continuous load, NEC requires applying the 125% rule, which means the OCPDs (fuse or circuit breaker) must be sized to handle at least 125% of the continuous current draw.

Continuous Load: 24A × 125% = 30A breaker
Non-Continuous Load: Can be served directly by a 30A breaker

According to NEC Table 210.21(B)(3), a 30A receptacle may serve a 30A branch circuit. Therefore, based on NEC 210.19(A)(1) and 210.20(A), the correct overcurrent protection (breaker size) for a NEMA TT-30 outlet is a 1-pole, 30A breaker (or a 1-pole, 30A GFCI breaker if GFCI protection is required).

How Many Watts Can a 30A, TT-30 Recpetacle Hold?

At 120 volts, a 30A receptacle can provide:

Maximum: 30A × 120V = 3,600 watts
Continuous load (80% rule): 24A × 120V = 2,880 Watts

Note: The continuous-load calculation should always use 120V for a TT-30 outlet, since it is a 125V single-phase receptacle, not 240V.

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

As mentioned earlier, a NEMA TT-30 outlet is rated for 30A maximum (24A for continuous loads under the 80% rule, or 30A continuous for industrial-grade receptacles).

For this ampacity, #10 AWG copper conductors are typically used and are suitable wire size for a 30A circuit, based on NEC Table 310.16 and CEC Table 2:

#10 AWG Copper Ampacity:

30A @ 60 °C (140 °F)
35A @ 75 °C (167 °F)
40A @ 90 °C (194 °F)

This makes #10 AWG copper the standard recommended wire size for a TT-30 receptacle.

For additional safety or long cable runs (to minimize voltage drop), you may choose #8 AWG copper with a 30A breaker.

Ground Wire Size

For a circuit protected by a 30A overcurrent device, the equipment grounding conductor (EGC) should be #10 AWG copper, as required by NEC Table 250.122.

Cable Type

Indoor (dry location): 0/2 NM-B – Standard Romex for indoor wiring.
Outdoor (direct burial): 10/2 UF-B – Outdoor-rated underground feeder cable. No conduit required if directly buried at correct depth (typically 24″).
Outdoor (in conduit) Individual: THWN/THWN-2 conductors through PVC or EMT conduit.
Always follow NEC ampacity tables and adjust for distance, ambient temperature, or conduit fill.

Can You Install NEMA TT-30R in 240V AC Circuit?

No – you must not install a NEMA TT-30R on a 240V AC circuit.

NEMA TT-30R is rated for 125V, 30A, single-phase only. The receptacle has one hot, one neutral, and one ground & it is designed for 120V loads only. Supplying 240V to a TT-30 receptacle will send 240V to the RV, which can destroy appliances, converter/charger, air conditioner, and electronics inside the RV.NEC Article 406.4(D) prohibits installing receptacles on circuits with a different voltage rating than the receptacle itself.

If 30-amp in a 240V single-phase supply is required for RVs & EVs, a NEMA 14-30, 10-30 or 6-30 receptacle may be used instead.

Instructions, Precautions & Codes

Choose an industrial-grade TT-30R receptacle if it is used for continuous RV loads.
Prefer plug-in connections for RVs instead of hardwiring for safer disconnection and easier maintenance.
Do not use single-gang wall boxes. Use a 2-gang outdoor box with a NEMA 3R rainproof enclosure for outdoor installations.
According to the NEC Table – 310.16 and 210.24.(1), the correct Breaker and Wire size for a 30-Amp, TT-30 receptacle is #10 AWG copper.
Use #10-2 wires with ground for 120V, 30-Amp breaker and outlet/receptacle.
Use total #10-3 wires (including 1-hot, 1 neutral and 1 ground) for 120V, 30-Amp breaker and load circuits for TT-30R.
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.
The TT-30 can be used for 24A continuous load (80% of breaker rating), & 30A non-continuous load as per NEC 210.19(A), 215.2, and 230.42(A). Industrial-Grade TT-30R can safely handle 30A continuous load due to superior contact and terminal construction.
It is against code to draw 30A from a 20A or 25A breaker using a TT-30 receptacle and smaller conductors (e.g., 12 AWG or 14 AWG) on a 30A 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, 120V TT-30 receptacles must be installed on a dedicated 30A breaker (standard or GFCI)
A 30A circuit can be used as a feeder to power multiple smaller circuits (15A or 20A) as permitted by NEC 551.71, but must be properly protected and sized.

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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