Appliances Electrical Loads Types and Classifications

In a previous Topic, “Electrical Load Classification and Types”,I show that the electrical loads can be classified into various categories according to various factors; one of these factors is according to load function/usage as follows:

Third Classification: Electrical Load Classification According To Load Function
  1. Lighting Load. 
  2. Appliances Load. 
  3. Power Loads.

In the following previous Topics, I explained the first type; lighting load:

And today, I will explain the second type of electrical loads according to the load function / usage as follows.

You can review the following previous topics for more information and good following:

2- Appliance electrical loads:

Appliance electrical load is the load which the electrical designer can’t specify its actual requirements because it doesn’t serve any particular load and subjected to the consumer needs.

This generally excludes building energy that is attributed to major end uses (HVAC, lighting, water heating, etc

Appliance electrical loads can be called as one of the following names:
  • Plug loads: devices that plug into a facility’s electrical system and powered by means of an ordinary AC plug or any electrical equipment that is plugged into a wall outlet. 
  • Receptacle loads: equipment loads normally served through electrical receptacles 
  • Unregulated loads.
  • General Purpose loads.
  • Miscellaneous loads.
  • Process energy/loads.

Examples of Appliance electrical loads:

  • Home equipment (home entertainment centers, kitchen electronics such as microwaves and toaster ovens, bath items such as hair dryers and electric hot tubs, and others such as security systems and ceiling fans).
  • Office equipment (e.g., computers, monitors, speakers, fax machines, printers and copiers). 
  • Workplace equipment (e.g., refrigerators, vending machines, audiovisual equipment, space heaters, coffee machines, and water coolers). 
  • Additional devices can add to the plug load (e.g., in a hospital, MRI and X-ray machines). 

Appliance electrical loads will be divided to:

1- General purpose loads (small appliance loads):

They are all the general purpose loads that can connect together without exceed a total load of 1500 VA in one circuit. Examples of those loads are:

  • home entertainment centers.
  • coffee machines.
  • water coolers.
  • electric iron.

2- Specialized appliance loads:

They are Loads that requires separate or dedicated electrical circuitry to avoid overload and special grounding methods that may be required because of their electrical load requirements determined and specified by the manufacturer of these appliances. Examples of These appliances are:

  • Computers and/or network servers.
  • Photocopiers.
  • Microwave ovens and other launch room appliances.
  • Vending machines.
  • x- Ray machines.
  • Water heaters.
  • Heating units.
  • Ranges.
  • Air conditioning units.
  • Cooking equipment.
  • Motors.
  • Galley equipment.
  • Arc welders.

Some important definitions:

Electrical Outlet: A point in the wiring system at which current is take to supply utilization equipment (There are lighting outlets and receptacle outlets)

  • Receptacle: is a contact device installed at the outlet for the connection of an attachment plug.

  • A single Receptacle: is a single contact device with no other contact device on the same yoke. 
  • A multiple Receptacle: is two or more contact devices on the same yoke. 
  • A duplex Receptacle: two receptacles installed and mounted by one strap or yoke. 
  • An individual branch circuit: is a branch circuit that supplies only one utilization equipment. 
  • Number of receptacles permitted on a circuit: is The maximum number of receptacle outlets permitted on a commercial or industrial circuit depends on the circuit ampacity. 

A branch circuit supplying only a duplex receptacle and no other device is not an individual branch circuit. 

Different types of Receptacles outlets:

A Receptacle outlet’s design may vary depending on the following:

  • Current supported.
  • The country of origin.
  • The type of equipment or plug it must accept.

  • Due to these variances, not all electrical outlets and electric-run components are mutually compatible. 
  • There are many types of Receptacles outlets found throughout the world; therefore it is important to know the differences in outlet types and voltages found in various countries which are represented in the following pictures: 


  • There are adapters and converters available that allow otherwise non-compatible electronics or components to plug in to electrical outlets found in other countries. 

NEMA Receptacles & Plugs Configurations:

NEMA connectors are AC power plugs used for mains electricity in North America and other countries that use the standards set by the U.S. National Electrical Manufacturers Association.

There are two basic classifications of NEMA device as follows:
1- Straight-blade types: are intended for supplying lighter-duty, general-purpose electrical devices.

2- Twist-locking types: are used for heavy industrial and commercial equipment, where increased protection against accidental disconnection is required. Numbers prefixed by (L) are curved-blade, twist-locking connectors; others are straight blade and non-locking. 

The following pictures will list all the configurations for NEMA receptacles and plugs:

NEMA receptacles and plugs configurations 
  • The numeral preceding the hyphen in NEMA nomenclature indicates the configuration, that is, the number of poles, number of wires, voltage, and whether single- or three-phase. A grounding type of device will be described as two-pole, three-wire; or four-pole, five-wire; etc. A non-grounding device will be two-pole, two wire; or three-pole, three-wire; etc.
  • The numeral following the hyphen is the rating of the device in amperes. The number is followed by the letter R to indicate a receptacle (female connector) or the letter P to indicate a plug (male connector). 

As an example,
  • The 5–15R is the common 125 V two-pole, three-wire receptacle. 
  • While the L5–15R, while sharing the same electrical rating, is a locking design that is not physically compatible with the straight-blade 5–15 design. 
  • And the 5–30 has the same two-pole, three-wire configuration and 125 V rating, but is rated 30 A. 

  • Although there are several non-grounding device types in the NEMA standards, only three of them are in widespread use today. These are the two-pole 1-15, and the three-pole 10–30 and 10–50. 

Tips for designing criteria of general purpose loads (small appliance loads):
  1. Divide areas by function for estimating small appliance loads. 
  2. Determine the extent of using the small appliances in each area by its occupants for best design of required small appliance loads for a specific area. I.e. some areas like an office may demand about 1 W/sf but could vary from a low of 0.5 W/sf to a high of 1.5 W/sf depending on the specific tasks to be performed by the office occupants. 
  3. Multiply the place area (in square feet) by the suitable demand (in W/sf) to get the small appliance load for a certain place. 

Tips for design criteria of specialized appliance loads:
  1. The owner or architect should give the electrical designer manufacturer electrical specification sheets for all the specialized equipments in a given facility. 
  2. The owner or architect should give the electrical designer a floor plan showing the location of all specialized equipment in the facility, so that the electrical designer can create an equipment list. 
  3. The electrical designer makes the equipment list which determines the electrical requirements of specialized equipments and machinery by gathering the following information: 
  • A brief desription of each piece of equipnts 
  • Specific electrical requirements for each piece of equipments including : 
  1. Horsepower.
  2. Voltage.
  3. Number of phases.
  4. Load ( in amperes or KW).
  • Floor plan indicating the location of each piece of equipment. 
  • Then, the electrical designer calculates the required number of branch circuits necessary to serve each piece of equipment. 

Note: You don't do all receptacle load calculations the same way. The NEC has separate requirements, depending on the application and this will be explained later in courses EE-2: Basic Electrical design course – Level I & EE-3: Basic Electrical design course – Level II Along with method s of receptacles distributions in different locations, sizing the receptacles rating and receptacle branch circuit calculations.

Receptacles Grades:

Receptacles are marketed using terms such as:

  • General grade.
  • Specification grade.
  • Heavy duty grade.
  • Industrial grade.
  • Commercial grade.
  • Residential grade.
  • Hospital grade.
  • Specialty grade.
  • Federal specification grade.

These designations represent the manufacturer’s attempt to assist in the selection process of an appropriate straight blade receptacle based upon the intended usage and demands that may be placed on the device. While they may be helpful to the user, these designations generally have no impact on the safety requirements applicable to the receptacles.

i will explain each grade of receptacles in detail in Course  EE-2: Basic Electrical design course – Level I.

in the next Topic, I will explain the Large Power Loads in buildings. so, please keep following.

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