How to Wire a 3-Phase, 60A – 120/208V NEMA 18-60 Receptacle

Electrical Technology

How to Install a NEMA 18-60, Three-Phase, 60A – 208Y/120V Non-Grounding Receptacle with Breaker and GFCI Protection

A NEMA 18-60 receptacle is a heavy-duty, industrial-grade straight-blade non-grounding receptacle designed for a 60A, 120/208V, 3-Phase Wye (Y or Star) power supply system. It is a heavy-duty, industrial-grade straight-blade receptacle designed for high-current commercial and industrial applications where both line-to-line and line-to-neutral loads are present. For instance, industrial machinery, process equipment, large HVAC units, and commercial power distribution equipment etc.

The NEMA 18-60 is a 4P, 4W non-grounding receptacle rated for 60A at 120/208V – 3-ΦY. It is wired using three hot (phase) conductors and one neutral conductor i.e. it does not need equipment grounding conductor. The three terminals (X, Y, Z) connects to the lines or “hot” wires i.e. (L1, L2, L3) and the (W) terminal connects to the neutral.

The 18-60R is available in industrial-grade, straight-blade, flush-mount and surface-mount configurations from manufacturers such as Hubbell, Leviton, and Eaton, and is commonly used where heavy-duty 3-phase loads are operated at mixed voltage.

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Terminals

There are four terminals in a 18-60 receptacle as follows:

W Terminal – Vertical Slot (I) – Silver Screw: Connects to the Neutral
X Terminal – Vertical Slot (I) – Brass Screw: Connects to HOT 1 (Line 1)
Y Terminal – Vertical Slot (I) – Brass Screw: Connects to HOT 2 (Line 2)
Z Horizontal Slot (➖) – Brass Screw: Connects to HOT 3 (Line 3)

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Electrical Ratings & Specifications

NEMA: NEMA 18-60R – Straight-Blade Receptacle
Poles: 4-Poles, 4 Wires – Non-Grounding – with Neutral
Voltage: 120/208V – Three-Phase Y – AC Supply – 60 Hz
Current: 60A
Breaker / GFCI: 60A
Wattage: ≈ 20 – 12.5kW
Wire Size: #4-#6 AWG Copper
Grade & Material: Commercial Grade – Nylon with Galvanized Steel Plate & Brass Contacts
Mounting: Flush Mounting
Termination: Back Terminal Screws
Outdoor Box: 2-gang outdoor box – NEMA 3R rainproof enclosure
Wiring: Hardwired / Dedicated Circuit

Wiring NEMA 18-60 with a 3-Pole Breaker

The following wiring tutorials illustrates how to wire a NEMA 18-60 receptacle rated at 60A – 120/208V, 3-Φ Y with a 60A 3-pole standard or GFCI breaker.

Step 1: De-energize the panel or load center at the main disconnect. Verify absence of voltage using an approved tester. Snap the 60A, 3-pole breaker onto the panel’s A-B-C phase busbars as shown in the fig. Before doing so, confirm the breaker is rated for 120/208V – 3-phase Y operation.

The 3-pole breaker connects to the phase conductors as follows:

L1 (Phase A) to the breaker pole 1
L2 (Phase B) to the breaker pole 2
L3 (Phase C) to the breaker pole 3

Torque terminals per breaker manufacturer specifications.

Step 2. Terminate the neutral conductor on the panel neutral bar. Ensure the neutral bar is bonded only at the service disconnect (main panel) and isolated in a subpanel.

Do NOT connect an EGC to the receptacle, as it is a non-grounding type. Meanwhile, grounding of raceways and enclosures must still comply with NEC Article 250.

Step 3: Run the 3-phase branch circuit conductors to the receptacle junction box in EMT as follows:

Pull (3) #4AWG (or #6) copper (THHN/THWN-2) for hot wires
Pull (1) #10 AWG ground wire

Step 4: Strip conductors to manufacturer-specified length and connect the three-phase branch circuit conductor to the NEMA 18-60 receptacle as follows:

L1 (Hot 1) to the X terminal
L2 (Hot 2) to the Y terminal
L3 (Hot 3) to the Z terminal
Neutral to W terminal

Torque all terminals precisely about 25 in.-lb (3 N·m) or as specified by the manufacturer. For outdoor applications, Install the receptacle securely into the 2-gang NEMA 3R outlet box.

Step 5: Install the cover plate and label the circuit at the panel as “NEMA 18-60 – 120/208 V, 3-Phase, 60 A – Non-Grounding”. Verify enclosure bonding per NEC 250.

Now energize the breaker and measure voltages:

L-L: ~208 V
L-N: ~120 V

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Wiring NEMA 18-60 with a 3-P GFCI

A 3-pole GFCI breaker works exactly like a normal 3-pole breaker except for the white built-in pigtail. In this case, connect the three-pole GFCI as follow:

L1 → GFCI breaker terminal 1
L2 → GFCI breaker terminal 2
L3 → GFCI breaker terminal 3

As NEMA 16-60 has no ground, hence do NOT connect the equipment grounding conductor (EGC) to the load. Connect the GFCI white pigtail wire to the neutral busbar in the main panel as shown in the following wiring diagram.

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Good to Know: Even though the receptacle doesn’t require EGC, the GFCI breaker must have its built-in pigtail connected to the neutral bar to monitor current imbalance between Lines and Neutral.

FAQs:

How Many Amps Can a NEMA 18-60 Handle Safely?

A NEMA 18-60 industrial grade receptacle is rated for 60 amperes maximum. This rating applies to each phase conductor when supplied from a properly protected 60A, 3-pole overcurrent device.

How Many Watts Can a NEMA 18-60 Receptacle Hold?

For a 120/208 V, 3-phase Wye system, the maximum apparent power is calculated as:

P = √3 × V_L-L × I

Substituting values:

P = 1.732 × 208 V × 60A

≈ 21,600 W (21.6 kW)

This is equivalent to:

3 × (120 V × 60 A) = 21.6 kW

Actual usable power may be lower depending on load characteristics, power factor, and manufacturer requirements (such as Hubble NEMA 18-60 is rated for 12.5kW).

Which Breaker Size Is Suitable for a NEMA 18-60 Receptacle?

The correct overcurrent protection is 60A, 3-pole circuit breaker or GFCI, rated for 120/208V, 3-phase. The breaker must be listed and compatible with the panelboard and intended application.

What Is the Correct Wire Size and Cable Type to Use with a NEMA 18-60?

The suitable wire size for copper conductors (per NEC Table 310.16, 75 °C terminals):

Phase conductors (L1, L2, L3): #6 AWG Cu
Neutral conductor: #6 AWG Cu (neutral must be full-sized due to possible unbalanced current in a Wye system)

For 75 °C temperature rating, the correct wire size for 60A circuit for each ungrounded conductor is #4AWG based on NEC Table 310.16.

Aluminum alternative:

#4 AWG Al (where permitted and properly terminated)

Common wiring methods:

Individual THHN/THWN-2 conductors in metallic conduit, or
Approved multi-conductor cable assemblies rated for 60A, 120/208V, 3-phase.

Instructions, Precautions & Codes

NEMA 18-60 is a three-phase outlet used in industrial and commercial setting.
18-60R are hardwired on a dedicated circuit.
Use a 2-gang – NEMA 3R rainproof enclosure for NEMA 18-60, especially for outdoor applications.
According to NEC Table – 310.16, the correct wire size for a 60A circuit and receptacle is #4 AWG copper. Likewise, the appropriate breaker size is a 60A, 208Y/120V, three-pole breaker (or 60A 3-P, GFCI breaker).
NEMA 18-60 (as an industrial grade) can supply max 60A for both continuous and non-continuous loads.
Use #4/3 cable (3 Hots + 1 neutral) for wiring a 3-phase NEMA 18-60 receptacle with a 3-pole breaker or GFCI rated for 120/208V.

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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