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What is the Suitable Wire Size for 50A Breaker and Outlet?

Electrical Technology
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How to Determine the Correct Wire Size for a 50A Breaker and Load Circuits Based on NEC?

50-Amp breakers and outlets are heavy-duty circuits and used for high power usage equipment such as hot tubs, spas, EV’s charging stations, campers and RV’s, air conditioner condensers, electric stoves and ranges, cooktops, water heaters, and other HVAC applications. 50A standard size outlets and breakers are available in both 1-pole and 2-pole configurations. They are used in 120V, 240V, and other voltage systems. In following technical article, we will demonstrate how to determine the correct wire size for a 50A breaker and load circuit in AWG for personal and circuit protection in compliance with the National Electrical Code (NEC) NFPA 70.

The correct wire size for a 50-amp circuit is #6 AWG copper or #4 AWG aluminum according to NEC tables and charts. Keep in mind that the correct wire size depends on multiple factors such as voltage drop. circuit run i.e. distance, type of cable and wire, type of insulation, ambient temperature etc. Consult a lichened electrician to ensure the proper wiring installation with correct wire size and compliance with NEC.

Correct Wire Size for 50 Amp Breaker

What is the Right Wire Size for a 50A Breaker and Outlet?

The standard wire size for a 50-ampere breaker is #6 AWG copper wire according to NEC Table 310.15(B)(16) (formerly Table 310.16)

Other than copper, you need to use a #4 AWG aluminum wire with a 50-amp circuit because aluminum has higher resistance and lower conductivity compared to copper.

Both #6 AWG copper and #4 AWG aluminum wires can safely handle:

  • 55A at 60°C (140°F)
  • 65A of current at 75°C (167°
  • 75A at 90°C (194°F)

Due to the heavy-duty nature of the circuit, you should use #6 gauge solid copper wire instead of #4 gauge aluminum or stranded wire with 50A breakers, outlets, and load circuits to ensure safety, better conductivity, and overall efficiency. Solid wire has several advantages over stranded wire, which is why U.S. homes typically use solid wire instead of stranded wire.

Good to Know:

  • For a 50A circuit breaker, the correct wire size is #6 AWG for copper and #4 AWG for aluminum.
  • A 50A breaker are used for single appliance as dedicated circuit for high-power devices. Same is the case for 50A outlets i.e. a 50-amp outlet should be used for single device.
  • Use 14-2 with ground for 120V, 50-Amp breaker and outlet.
  • Use 14-3 with ground for 240V, 50-Amp breaker and outlet.
  • Use 14-4 with neutral and ground for 240V, 50-Amp breaker and outlet (such as NEMA 14-50R).
  • You may use a 50-amp, 240V outlet on a 50-amp breaker only.
  • You may use A 50A, 240V outlet as dedicated circuit for single unit only.
  • 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.

  • 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 or breaker to the load point) to counter the voltage drop.

Related Post: What is the Correct Wire Size for a 40A Breaker and Load?

How to Select the Right Wire Size for a 50A Breaker and Outlet?

The following example demonstrate the selection of correct wire size for a 50A breaker and outlet used for both continuous and non-continuous load circuits

Example:

Determine the correct wire size for a 50-Amp (either 1-pole or 2-pole) breaker and outlets used for both continuous and non-continuous load circuits according to NEC guidelines.

Continuous Load Circuit

The NEC’s 125% rule states that the maximum overcurrent protection (MOCP) should handle 125% of the continuous load. As a safety factor, no more than 80% of the continuous load should be connected to the Overcurrent Protection Device (OCPD).

50A × 80% = 40A

Based on this rule, the amperes of the load circuit should not exceed the maximum limit of 40A. Alternatively, you may only wire a 40-Amp of continuous load (which lasts for 3-4 hours simultaneously such as water heaters) circuit to a 50-Amp breaker and outlet/receptacle.

If you know the amperage of the load circuit (for example, if the nameplate of a device shows a minimum circuit ampacity (MCA) of 40A) and you want to find the correct breaker size for the 40A circuit, simply apply the 125% rule as follows.

40A × 125% = 50A

According to NEC Table 310.15(B)(16), the #6 AWG copper wire size can carry 55A at 60°C (140°F) and 65A at 75°C (167°F) which falls in the range of 50A breaker and receptacle/outlet.

Non-continuous Load Circuit

For non-continuous loads (e.g., general lighting circuits), the conductor size should be no less than 100% of the load. The same applies to overcurrent protection devices (OCPDs).

This way, a 50A breaker can handle a maximum of 50A non-continuous load circuits, such as outlets and lighting circuits, while considering distance and ambient temperature rating (Refer to 110.14(C) and 310.15(B)(2)).

How Many Amps Can a 50A Breaker and Outlet Handle Safely?

A 50-amp breaker safely handles a maximum of 50 amps of current. The NEC specifies that you should not load breakers to more than 80% of their rated capacity for continuous loads (defined as a load lasting three hours or more). Therefore, you should use a 50A breaker for a maximum of 40A continuous load circuits.

50A × 80% = 40A

For short, non-continuous loads, the breaker can handle up to 50 amps safely.

  • Use a 50A breaker for a 40A continuous load circuit.
  • Use a 50A breaker for a 50A non-continuous load circuit.

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

The above calculations are based on NEC Table 310.15(B)(16) and 240.4(A) through (G). These codes illustrate that the 8 AWG copper wire size can carry 40A at 60°C (140°F) and 50A at 75°C (167°F) which is the suitable size to use with a 50-Amp breaker and outlet. Other than copper, you may use #4 AWG for aluminum wire which has the same ampacity rating as #6 AWG copper at the same ambient temperature.

How Many Watts Can a 30A Breaker and Outlet Hold?

You can calculate the power capacity of a 50-amp breaker and outlet using the following formula:

120V Circuit

In a standard 1-Pole, 120V circuit, the max power a 50A breaker and outlet can hold:

50 A × 120 V = 6,000 W

Applying the safety factor (80% load):

50 A × 80% = 40 A

This way, you may connect up to 4.800 watts of resistive load circuit to a 50A breaker and outlet.

40A × 120V = 4,800 watts

It allows to use 50A breaker with NEMA-5-50R, 6-50R e.g. for dryer or other 120V, 50A outlets. In simple words, you can use a 50A breaker for 120V, 4.5kW to 4.8kW electric / space water heater elements or other resistive load circuits.

Good to know: The highest allowed outlet you can use on a 50A breaker in a 120V circuit is 50A i.e. NEMA-5-50R, for example for a 120V dryer.

240V Circuit

A 2-Pole, 50A breaker and outlet in 240V circuit can hold the maximum power:

50 A × 240 V = 12,000 W

Applying the safety factor of 80% for continues load:

50 A × 80% = 40 A

No more than 9,600 watts of load should be connected to a 2-pole, 240V, 50A breaker and outlet:

40A × 240V = 9,600 watts

This allows you to use a 50A breaker with a 240V, 9kW to 9.5kW electric ranges or water heater elements.

These calculations assume that the breaker is not continuously loaded to 100% of its capacity. For continuous loads, the safe wattage is 80% of these values:

  • 120V Circuit (Continuous Load): 4,800 W
  • 240V Circuit (Continuous Load): 9,600 W

How Many Outlets Can be Put on a 50A Breaker?

50A breaker are generally used for dedicated circuit and outlet for high wattage appliances such as electric ranges, water heaters. It is against the code to use 50A breakers to wire with a number of 15A and 20A outlets.

Based on a general assumption and calculation of ampacity, you can connect a 40A maximum safe current load to a 50A breaker. If each outlet draws 1.5A of current:

40 A ÷ 1.5 A ≈ 26 outlets

Keep in mind that 50A breakers are hardwires as dedicated circuits without receptacles and outlets. In other words, you may use it for one device per outlet. For more details, Refer to NEC Table 210.21(B)(3) for receptacle ratings for various circuit sizes.

Related Post: What is the Correct Wire Size for 25A Breaker and Load?

It is Allowed to Use a 40A Outlet on a 50A Breaker?

No, it is not allowed to use a 40A outlet on a 50A breaker. According to NEC, it is allowed to use a 50A outlet on a 40A breaker, but it’s not advisable to use a 40A outlet on a 50A breaker. Here’s why:

  1. NEC Compliance: The National Electrical Code (NEC) requires that the outlet rating must be equal to or greater than the breaker rating to ensure proper protection. A 40A outlet on a 50A breaker would violate this, as the breaker could allow more current (up to 50 amps) to flow through the outlet than it is designed to handle. NEC Article 210.21(B)(3).
  2. Overload and Fire Risk: A 40A outlet is designed to handle only 40 amps of non-continuous load and max of 32A of continuous load – NEC 210.19(A)(1). If a 50A breaker is installed with a 40A receptacle, and a load exceeding 40 amps is connected, the breaker would not trip at the correct point, potentially allowing the outlet, wire and cables, and the connected equipment to overheat, creating a fire hazard.
  3. Correct Pairing: The breaker protects the circuit, wiring, and outlet from overcurrent. For a 50A breaker, you should use an outlet rated at 50 amps or higher.

Always ensure the breaker, wiring, and outlet ratings match appropriately for safety and code compliance.

What is the Suitable Types of Cables for a 50A Breaker and Outlet

When selecting cables for a 50-amp breaker and outlet, it is crucial to choose a conductor that can handle the current without overheating. The appropriate cable size depends on the conductor material (copper or aluminum) and the insulation type.

Copper Conductors:

    • 6 AWG Copper Wire: This is typically used for 50-amp circuits. It offers a good balance between flexibility and current-carrying capacity.
    • Insulation Types: THHN (Thermoplastic High Heat-resistant Nylon-coated) or THWN (Thermoplastic Heat and Water-resistant Nylon-coated) are commonly used due to their durability and high-temperature rating.

Aluminum Conductors:

    • 4 AWG Aluminum Wire: Because aluminum is less conductive than copper, a larger wire size is required to carry the same current.
    • Insulation Types: Similar to copper, THHN or XHHW (Cross-linked High Heat Water-resistant) insulation is recommended for aluminum conductors.

Applications of 50-Amp Breakers and Outlets

50-amp breakers and outlets are typically used in applications that require higher power consumption. Some common applications include:

  • Residential RVs (Recreational Vehicles): 50-amp outlets are standard for RV parks, providing adequate power for large RVs equipped with multiple appliances like air conditioners, refrigerators, and microwaves.
  • Electric Ranges & Water Heaters: Many electric stoves, ovens and water heaters require a 50-amp circuit due to their high power demands.
  • Hot Tubs and Spas: Hot tubs and spas often require a 50-amp breaker to safely handle the power needed for heaters and pumps.
  • Subpanels: A 50-amp breaker is sometimes used to feed a subpanel, especially in a detached garage or workshop, where multiple circuits might be needed.
  • EV (Electric Vehicle) Chargers: Some Level 2 EV chargers require a 50-amp circuit to provide faster charging times.

Related Post: What is the Right Wire Size for 15A Breaker and Outlet?

Good to Know:

  • The ampere rating of a single receptacle installed on an individual branch circuit should not exceed that of the branch circuit.
  • The above calculations for breaker and wire sizes apply only to purely resistive load circuits, such as lighting.
  • For inductive loads (motors and HVAC), refer to NEC Article 440, particularly sections 440.22 and 440.32. If not sure, consult an HVACR contractor, instructor, and electrician.
  • A 50A branch circuit needs #6 AWG wire size for copper or #4 AWG for aluminum – NEC Table 310.15(B)(16) (formerly Table 310.16) and 210.24.(1).
  • You can use a 50A breaker and outlet for a 40A continuous load and a maximum 50A non-continuous load, according to NEC sections 210.19(A), 215.2, and 230.42(A).
  • It is against code to use a 50A outlet to draw 50A on a 45A breaker.
  • It is against code to use smaller gauge wire sizes (e.g., using 10, 8 AWG) instead of 6 AWG wire with a 50A breaker and receptacle.
  • According to NEC 210.21(B)(3), it is permissible to use a 40A or two 50A outlets on a 50A circuit if there are multiple receptacles on the circuit and only one operates at a time while the toral current should not more than 50A.
  • Important Note: When you install a 50A outlet on a 50A circuit, you should dedicate it to a single appliance or outlet with a maximum 40A load. Drawing more than 40A simultaneously from a 50A breaker or outlet will overheat the circuit, potentially causing serious injury and fire hazards.

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