How to Wire a 20A/250V, NEMA 2-20 Non-Grounding Receptacle

Electrical Technology

How to Replace a 20A – 250V, NEMA 2-20 Non-Grounding Receptacle with a 2-P Breaker

The NEMA 2-20 is a non-grounding 2-wire receptacle rated for 20 amps and 250 volts. It belongs to the NEMA 2-series family used primarily in North America and Canada.

The NEMA 2-20 configuration is considered obsolete and unsafe by modern electrical standards. It was used in early two-wire 250V systems that did not include a grounding conductor. Currently, NEC no longer allows these kind of non-grounding outlets and receptacles for most installations. Currently, they are available from various manufacturers, such as Hubbell, and can be used as replacements for existing damaged outlets.

NEC 406.4(D)(2) and 250.130(C) allows the replacements of ungrounded (non–grounding-type (2-wire) receptacle)) under the following three options:

Replace with another non–grounding-type receptacle. Only if there is no equipment grounding conductor (EGC) present in the circuit.
Replace with a GFCI-type receptacle. The GFCI must be marked “No Equipment Ground”. GFCI provides shock protection, but not an actual ground path.
Replace with a grounding-type (3-prong) receptacle protected by a GFCI device (either the receptacle itself or upstream i.e. GFCI breaker). The new receptacle must also be marked “GFCI Protected” and “No Equipment Ground.” even in the absence of equipment grounding conductor (EGC).

Good to Know: Under NEC 406.4(D)(2), if a non-grounding type receptacle (like NEMA 2-20) is replaced:

You must either install a grounded receptacle with a proper grounding conductor, or
Replace it with a GFCI-protected outlet and label it “No Equipment Ground.”

Table of Contents

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The NEMA 2-20 Receptacle

A NEMA 2-20 is a 250V, 20A non-grounding, two-pole, two-wire receptacle for use in older commercial and industrial settings. It features two slots (one vertical and one horizontal) for Hot 1 and Hot 2, designed to accept the two-prong plug of a NEMA 2-20P.

It is considered obsolete for new installations because of its lack of a safety ground, but it can still be found in older equipment and is used for repair purposes, though newer equipment rarely uses this configuration. Currently, NEMA 2-20R is superseded by grounded designs like NEMA 6-20 (2-pole, 3-wire, 250V grounded).

While no longer manufactured for standard use, you might still find NEMA 2-20 receptacles in old industrial buildings, workshops, vintage equipment and machinery from the 1950s-60s.

Terminals

There are two terminals in a 2-20R receptacle.

Hot 1: Black Wire → Brass Screw – Vertical Slot (I)
Hot 2: Red Wire → Brass Screw – Horizontal Slot (➖)

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Electrical Ratings & Specifications

NEMA: NEMA 2-20R – Straight-Blade Receptacle
Poles: 2-Pole, 2-Wire – Non-Grounding without Neutral
Wires: Two Wires – Hot 1 & Hot 2
Voltage: 250V – Single-Phase AC Supply – 60 Hz
Breaker: 20A
Current: 20A – 16A
Wattage: 4,800 W
Wire Size: #12AWG Copper
Grade & Material: Industrial Grade – Thermoplastic with Steel Strap & Galvanized Steel Screws
Termination: Side Wired Only
Mounting: Screw Mounting
Wiring: Hardwired / Dedicated Circuit

Wiring 15 Amp, Non-Grounding 2-Wire Receptacle

To replace an existing 2-wire non-grounding 20A, 250V receptacle, (NEMA 2-20R), connect the terminals of receptacle to a two-pole, 20A breaker in a 120/240V main panel as shown in the following wiring diagram.

Wiring Steps:

Use #14 AWG copper conductors, which is the appropriate wire size for a 20A circuit and compatible with the NEMA 2-20R receptacle.
Strip the ¾ inch (19 mm or 1.9 cm) insulation from the side wire conductors.
Connect Hot 1 wire (black) to the brass screw terminal, which corresponds to the vertical slot.
Connect Hot 2 wire (red) to the brass screw terminal on the other side, which corresponds to the horizontal slot.
After the connections, tighten each terminal screw to approximately 10-14 in·lbs (1.1-1.6 N·m) of torque.

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Good to Know:

As per NEC 406.4(D)(2): “Non–grounding-type receptacles shall not be replaced with grounding-type receptacles unless an equipment grounding conductor is provided.” In simple words, you can only replace a 2-wire (ungrounded) outlet with another 2-wire or a GFCI-type outlet labeled “No Equipment Ground.

FAQs

When Was the NEMA 2-20R Introduced and When Did it Become Obsolete?

The NEMA 2-20R was introduced in the early to mid-20th century for 250-volt, 20-amp two-wire (ungrounded) applications. It became largely obsolete by the late 1960s to early 1970s, following the introduction of grounding-type receptacles (such as NEMA 6-20R) mandated by electrical codes.

Why are NEMA 2-20 Receptacles Considered Outdated?

They are outdated because they lack an equipment grounding conductor (EGC), which is now a fundamental safety requirement. Grounding reduces the risk of electric shock and equipment damage. As the NEC and UL standards evolved, non-grounding 250V outlets like the NEMA 2-20 were phased out from residential and commercial installations.

Reason for obsolescence:

Lack of grounding conductor (no equipment ground for shock protection).
Incompatible with modern grounded appliances.
Superseded by grounded designs like NEMA 6-20 (2-pole, 3-wire, 250V grounded).

Modern standard replacement:

NEMA 6-20R – 250V, 20A, 3-wire grounded receptacle (Hot–Hot–Ground).

How Many Amps Can a NEMA 2-20 Handle Safely?

A NEMA 2-20 receptacle is rated for 20 amperes maximum under standard operating conditions as specified by NEMA. As per NEC Articles 210.19(A), the 20A outlet can be used for 16A continuous load (which runs 3 or more hours) and max 20A non-continuous load.

How Many Watts Can a NEMA 2-20 Receptacle Hold?

At 240 volts and 20 amps, a NEMA 2-20 receptacle can handle up to 4,800W

Watts = Volts × Amps = 250V × 20A = 4,800 watts (4.8 kW)

This is the maximum safe non-continuous load. The continues load can be reduced 80% which is equal to 3,840W.

Which breaker Size is Suitable for a NEMA 2-20 Receptacle ?

The right size breaker for NEMA 2-20 outlet is 15A two-pole breaker or GFCI.

What is the Correct Wire Size and Cable Type to Use with a NEMA 2-20?

Based on NEC Table – 310.16, the minimum wire size for a 20-amp, 250-volt NEMA 2-20 receptacle should be:

12 AWG copper (THHN or NM-B) – standard for 20A circuits.
10 AWG aluminum (if used, though not recommended for outlets).

Can I Replace a NEMA 2-20 with a NEMA 5-20, 6-20, or 14-20?

Yes & NO.

Replace with NEMA 5-20R (125V) – No, It is 120V device while NEMA 2-20 is 240V.
Replace with NEMA 6-20R (250V) – Yes, if it is a 2-wire 250V circuit and a grounding conductor is available. Otherwise, No.
Replace with NEMA 14-20R (125/250V)- Yes, if a new 4-wire (hot-hot-neutral-ground) configuration is installed. Other wise NO.

According to NEC 406.4(D)(2), a 2-20 can only be replaced with another 2-20, a GFCI receptacle, or a GFCI-protected 2-20 marked “No Equipment Ground.”.

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, consult with a licensed electrician to ensure any electrical work is performed safely and in compliance with your local codes, as code requirements can vary.
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 it’s all about electricity and electricity is too dangerous.