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Types of Electrical Outlets: A Guide for Subcontractors

Published: November 30, 2022
Last updated: December 28, 2022
Read time: 4 minutes

Each type of electrical outlet serves a specific purpose. There are outlets for high-powered machines, outlets designed for indoor and outdoor use, and outlets that protect against electrical fires. 

As an electrical subcontractor, it’s important to know the various types of electrical outlets so that you can correctly source and install them in your project. This guide will discuss the types of electrical outlets, their functions, and how to install them.

What is an electrical outlet? 

An electrical outlet, also known as an outlet, electrical socket, or wall plug, is an opening or a series of openings connected to a wired power source to power an electrical device or appliance. Outlets are typically installed on walls and floors and come in various shapes and sizes. Electrical cords or plugs are inserted into outlets to provide electrical power to devices.

Types of Electrical Outlets

Electrical outlets are categorized as follows:

Standard receptacles

Standard receptacles are the most common type of outlet found in commercial establishments. They have two vertical slits and supply 120 volts of power. 

They are used for small electrical appliances. They usually have a round opening in the center of the vertical slits to accommodate a three-pronged plug.

Ground Fault Circuit Interrupter (GFCI) receptacles

GFCI receptacles are usually installed in areas that can get wet, and there is a risk of electrical shocks, such as in bathrooms and other wet areas. GFCI outlets have a built-in circuit breaker to shut off power automatically without shorting the rest of the building if there is an electrical current leakage. 

They have two vertical slits and a semi-circular hole with a test and reset button in black and red. As per 210.8 of the National Electric Code, you must install GFCI protection for all 15A and 20A, 125V receptacles in bathrooms, rooftops, and kitchens in commercial/industrial facilities.

Isolated-Ground Receptacle

These electrical outlets are used in places where electrical noise from other devices can interfere with sensitive equipment. Isolated ground receptacles have special construction and wiring and feature a small orange triangle. They are usually used in large installations like hospitals to combat noise interference. These special receptacles 

Split-Wired Receptacle

These electrical outlets have two independent sections with one hot wire. They are commonly used for lamps with a night light feature, as a switch can control the bottom outlet.

Electrical Outlet Types

Standard duplex

This is the most common type of electrical outlet in commercial buildings. A duplex electrical outlet has two receptacles, each face containing vertical slits, and usually has a semi-circular hole at the bottom for three-pronged plugs. This outlet can handle different amounts of power and voltages and can be tamper-resistant and weather resistant. 

Combination High/Low Voltage

These have two independent sections that can handle different voltages. One side is used for high-voltage devices such as air conditioners, while the other is for low-voltage devices such as computers and televisions. 

Single Grounded 15 Ampere

These can only be used for devices that require a single 15-ampere circuit. They have two vertical slits and a semi-circular hole at the bottom. They are commonly used for lighting installations but cannot cover high electrical loads. 

30 Ampere

30 Amp outlets are used for devices that require a 30-ampere circuit and have three prongs, one for ground, one for hot, and one for neutral. They are used for heavy electrical loads.

50 Ampere

These industrial-grade outlets have four prongs; two for hot, one for ground, and one for neutral. They are used in large electrical loads such as air conditioners and welding equipment. 

Twist Lock

These are designed for heavy electrical loads and include a locking mechanism to prevent the plug from being disconnected accidentally. They differ in amps, wire count, pole count, and NEMA (National Electrical Manufacturers Association) ratings. These electrical outlets are used in commercial and industrial facilities to connect electrical equipment such as generators, air compressors, and other heavy industrial and commercial equipment that is vibrating or in a harsh environment.

Single Grounded 20 Ampere

These are designed for devices that require a single 20-ampere circuit. They have a T-shaped prong, one vertical slit, and a semi-circular hole at the bottom. These are intended for high electrical loads but not as much as a 30-ampere electrical outlet.

50 Ampere Floor Mount

These are mounted on the floor and used for devices requiring a 50-ampere circuit. They have two hot, one ground, and one neutral prong. These electrical outlets are typically used for heavy electrical loads in industrial and commercial facilities.

Fuse/Receptacle Combination

These outlets have a built-in fuse that protects the circuit from overloading and are commonly used in commercial applications.

Isolated-Ground Duplex

These are Isolated-Ground Receptacles just divided into two sections with one hot wire.

Ground Fault Circuit Interrupter (GFCI)

These outlets have a built-in circuit breaker that trips the circuit when an imbalance in the electrical current is detected. These electrical outlets prevent electrical shocks in damp environments.


These electrical outlets are protected on a GFCI circuit and designed for outdoor use. They are built to withstand weather and environmental conditions. 

Surge Protection (TVSS)

These electrical outlets protect electrical equipment from voltage spikes. TVSS directs excess voltage into the grounding wire, preventing it from damaging electrical equipment.

Switch & GFCI Combination

This type of outlet combines a GFCI with a switch to provide ultimate protection against electrical shocks. 

How to install an electrical outlet 

As a subcontractor, you probably know how to install an electrical outlet. But just in case you need a refresher, here’s a quick how-to guide: 

To install a standard electrical outlet, you will need the following: 

  • Electrical wire 
  • Electrical tape 
  • Writing utensils
  • Wire cutters
  • Needle nose pliers 
  • Voltage tester
  • Screwdriver 
  • Outlet box 
  • Standard outlet
  • Wall plate 
  • Ground wire 
  1.  Find an existing power source to connect your new outlet.
  1. Once you’ve found a power source, identify the location of the new outlet and map out the path the electrical wire will need to take to reach the outlet box. 
  1. Trace the electrical outlet box onto the wall to mark the location. Cut a hole in the drywall using a utility knife or saw. 
  1. Turn off the power to the circuit you will be working on at the main electrical panel for safety. Use a voltage tester to ensure the power is off before you begin working.
  1. Take the cover off the power source outlet and unscrew the electrical wires. 
  1. Strip about an inch of insulation off the power source’s electrical wire using wire strippers, which we’ll call pigtails, to reconnect your power source outlet.
  1. Connect the pigtail wires to the circuit wires using a wire connector. Connect the bare copper pigtail to the ground (bare wires), the white to the neutral wires, and the black to the hot wires.
  1. Using needle-nose pliers, form a J-shaped hook at the tip of each wire and fit the hooked end around the ground screw on the new receptacle in a clockwise fashion. Squeeze the hook, then tighten the ground screw with a screwdriver.
  1. Now, attach the neutral and hot wires to the receptacle. 
  1. Attach the receptacle to the box by pressing the receptacle’s mounting strap against the box and securing it with the mounting screws.
  1. Attach the wall plate to the electrical outlet and turn the power back on to ensure it works correctly.

If you are not one, please consult a licensed electrician before handling receptacle outlets. 

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