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How to Wire a 50A, NEMA 10-50 Non-Grounding Receptacle

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How to Replace a 50A, 125/250V, NEMA 10-50 Receptacle with a 2-P Breaker in Existing Installations

The NEMA 10-family (10-20, 10-30, and 10-50) has been obsolete since 1965. These receptacles were commonly used for ranges and dryers until 1996. in 1997, NEC switched from NEMA 10 to 14-series. Some in the welding community still use NEMA 10-series outlets and receptacles, but doing so is now against code.

NEMA 10 devices can only be replaced when an existing receptacle is broken. In other words, NEMA 10 receptacles cannot be installed in new buildings or installations. If a replacement is required, it is safer to upgrade to a modern alternative, such as NEMA 6-50 or NEMA 14-50, which include proper grounding and (for 14-50) a neutral connection.

Good to Know: Since 2-wire non-grounding receptacles are no longer permitted for new installations, NEC 406.4(D)(2) and 250.130(C) allow their replacement only under the following conditions:

Replace with another 2-wire receptacle: You may replace the existing non-grounding receptacle with a new one of the same type.
Replace with a GFCI receptacle: A GFCI-type receptacle may be installed as a replacement. In this case, the receptacle must be clearly marked with the words “No Equipment Ground” and/or “GFCI Protected” to indicate that it is not connected to an equipment grounding conductor.
Replace with a grounding-type receptacle protected by a GFCI: A grounding-type receptacle may be installed if it is protected by a GFCI device, such as a GFCI circuit breaker or a GFCI receptacle located at the first outlet on the circuit. In this configuration, the GFCI provides shock protection even though an equipment grounding conductor (EGC) is not present.

When replacing a damaged NEMA 10-50 receptacle in an existing installation, ensure you use a 50A, 2-pole breaker or GFCI breaker if required by local code. Be aware that using a GFCI breaker with a 10-50R may lead to nuisance tripping (when neutral is bonded to the frame). This is because the receptacle lacks a separate ground wire to be properly compatible with GFCI.

NEC-250.140 (A) and (B) explicitly requires the use of a four-wire supply for electric ranges, ovens, and clothes dryers, which includes an equipment grounding conductor (EGC).
NEC 250.119(A), mandates the presence of a dedicated grounding conductor for all receptacle outlets, which the NEMA 10-50 two-wire, three-prong design lacks. This why alternative are used for safety concerns such as 14-50 or 6-50 instead of 10-50.

Table of Contents

The NEMA 10-50 Outlets & Receptacles

The NEMA 10-50R is a 50-amp, 125/250V, non-grounding receptacle. It is wired with two hot wires and a neutral wire and is designed to be used with a matching NEMA 10-50P plug. The “50” in 10-50R indicates the maximum current rating in amperes, while the “R” stands for “Receptacle.” Similarly, the “P” in NEMA 10-50P stands for “Plug.”

The NEMA 10-50 has a 3-pole, 3-wire configuration (Hot 1, Hot 2, and Neutral). It is a non-grounding, straight-blade device that does not include a dedicated grounding conductor. It has two angled hot slots (for Hot 1 and Hot 2) and one straight vertical slot for the neutral wire.

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Terminals

There are Three (3) terminals in a NEMA 10-50 receptacle:

X Terminal (Brass Screw): Connects to Black Wire – HOT 1 (Line 1)
Y Terminal (Brass Screw): Connects to Red Wire – HOT 2 (Line 2)
W Terminal (Silver Screw): Connects to the White Wire – Neutral Wire

Electrical Ratings & Specifications

NEMA: NEMA 10-50R – Straight-Blade Receptacle
Poles: 3-Pole, 3-Wire, Non-Grounding with Neutral
Wires: 3 Wires – Hot 1, Hot 2 and Neutral
Voltage: 125/250V Single-Phase AC Supply – 60 Hz
Breaker: 50A
Current: 40A – 50A
Wattage: 12,000 W
Wire Size: #6 AWG (Copper Only)
Temp. Rating: -40°C to 75°C (-40°F to 167°F)
Dielectric-strength: Withstand 2,000V Min.
Grade & Material: Industrial Grade – Thermoplastic
Mounting: Flush / Screw Mounting
Outdoor Box: 2-gang outdoor box – NEMA 3R rainproof enclosure
Wiring: Hardwired / Dedicated Circuit

Wiring NEMA 10-50R Outlet with 2P Breaker

A NEMA 10-50 can be installed as a replacement in an existing installation, either as a plug-in connection or as a hardwired connection.

As shown in the wiring diagram, connect Hot 1 (black) and Hot 2 (red) from the 2-pole, 50A breaker to the X and Y terminals of the NEMA 10-50 receptacle. Then, connect the neutral wire (white) to the W terminal in the 120/240V or 208/240V main panel.

Although the NEMA 10-50 receptacle can accept wire sizes ranging from #10 AWG to #4 AWG, #6 AWG copper conductors are recommended for a 50A circuit and associated 10-50R outlet.

Good Practice

Strip each conductor 1 inch (25mm) or refer to the stripe gage on mounting plate.
Tighten terminal screws to approximately 30 lb-in (3.4 N·m).

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While available in two variants, use an industrial grade instead of residential grade receptacles. For outdoor installations, use a NEMA 3R weatherproof (rainproof) 2-gang enclosure to protect the receptacle from moisture and environmental exposure.

Good to Know:

NEMA 10-50 is not for grounding use. Connect to non-grounding circuits only unless it is to be used for range or clothes dryer in accordance with NEC 250-60
NEC 210.8 requires GFCI protection for the outlets especially in garage, basement, outdoors, laundry and wet areas etc.
According to NEC 210.8(A)(1) through (A)(11), all outdoor receptacles must be installed downstream of GFCI protection, in compliance with Articles 426.28 or 427.22.
Keep in mind that nuisance tripping may occur in case of using GFCI breaker with non-grounding receptacle whenever neutral is bonded to the frame. In such cases, follow the manufacturer’s recommendations to avoid overlapping protection.

FAQs:

How Many Amps Can a NEMA 10-50 Handle Safely?

A NEMA 10-50 receptacle is rated for 50 amps maximum, but per NEC guidelines, it can safely handle up to 40A continuous load (80% rule) and 50A non-continuous load.

If it is an industrial grade, you may use it for 50A continuously without overloading.

How Many Watts Can a NEMA 10-50 Receptacle Hold?

On a 240V circuit, a 10-50 receptacle can deliver up to 12,000 watts (12 kW) (50A × 240V). For continuous loads, limit to 9,600 watts (9.6 kW).

Which Breaker Size is Suitable for a NEMA 10-50 Receptacle?

A 50A, double-pole breaker is the correct choice for a NEMA 10-50 receptacle. Always use a breaker that matches the receptacle rating and wire capacity.

What is the Correct Wire Size and Cable Type to use with NEMA 10-50?

Based on NEC Table – 310.16, the correct wire size is #6 AWG copper (THHN/THWN in conduit) or 6/3 NM-B cable (if allowed) for a 50A circuit. Since NEMA 10-50 does not have a grounding conductor, follow local codes carefully as modern installations often require a 4-wire grounded receptacles such as NEMA 14-50 or 6-50.

Can You Use 10-50R for EV Charging?

No, you should not use a NEMA 10-50R receptacle for EV charging because it lacks a safety ground connection. Equipment grounding conductor is required by modern electric vehicle chargers (EVSEs) and current electrical codes.

The recommended and safe solution is to have a licensed electrician install a NEMA 14-50R or 6-50R receptacle, which includes the required ground wire.

Can you Install NEMA 10-50 In New Installations?

NO! The NEC no longer allows NEMA 10-50 receptacles for new installations because they lack a grounding conductor. They are only permitted for replacement in existing installations. For new installations, use a NEMA 14-50 or 6-50 or other grounded receptacle type for improved safety.

How Can I Replace a NEMA 10-50 with NEMA 6-50 without Running an additional Wire?

If you can’t run an additional wire, it is safely to remove the NEMA 10-50R and install a NEMA 6-50R. Simply, mark the Neutral wire with “Ground” (where ground is bonded to the neutral in the main panel) and connect to the Grounding terminal in 6-50.

This will work with EV chargers or ranges which do not need a neutral connection in 240V circuits.

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.

Resources:

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