In course " EE1: Beginners' Electrical design course " which is a preparation for beginners in electrical design, I explained the Electrical design philosophy for all building types and indicated the different types of buildings according to usage which were:
 Industrial buildings
 Commercial buildings
 Residential buildings
 Agricultural buildings
 Educational buildings
 Transportation buildings
 Religious buildings
 Parking and storage
 Military buildings
 Governmental buildings
 Cultural buildings
 Other buildings
In the current course" EE3: Basic Electrical design course – Level II ", in Sixteen Articles, I explained the design of the Dwelling type buildings; I explained Where and how to distribute each type of load in a dwelling unit as per NEC code and how to calculate its Demand load for feeder and service sizing calculations, and finally I summarize the steps of calculating electrical load for any dwelling unit as per NEC standard & Optional Calculation methods in two Excel sheets/calculator.
These Sixteen Articles for the electrical design of dwelling buildings are as follows:
 Branch Circuit Design Calculations – Part One
 Branch Circuit Design Calculations – Part Two
 Branch Circuit Design Calculations – Part Three
 Receptacle Branch Circuit Design Calculations – Part One
 Receptacle Branch Circuit Design Calculations – Part Two
 Receptacle Branch Circuit Design Calculations – Part Three
 Receptacle Branch Circuit Design Calculations – Part Four
 Receptacle Branch Circuit Design Calculations – Part Five
 Receptacle Branch Circuit Design Calculations – Part Six
 Receptacle Branch Circuit Design Calculations – Part Seven
 Branch Circuit Design Calculations – Part Eight
 Branch Circuit Design Calculations – Part Nine
 Branch Circuit Design Calculations – Part Ten
 Branch Circuit Design Calculations – Part Eleven
 Electrical Load Calculator for Dwelling Units
 Optional Electrical Load Calculator for Dwelling Units
Today, I will begin explaining the electrical design of NonDwelling Buildings as per NEC Code.
List of ordinary NonDwelling Buildings Loads:
Most of NonDwelling Buildings will have the following types of loads:
 Lighting loads,
 Receptacles Loads,
 Kitchen Loads,
 Heating, Ventilation and air conditioning Loads (NonCoincident Loads),
 Motor Loads,
 Other Loads.
Again, but for above NonDwelling Buildings Loads, I will explain the following points:
 Where and how to distribute each type of load in a dwelling unit as per NEC code?
 How to calculate its Demand load for feeder and service sizing calculations?
Important!!!
All design Calculations for Nondwelling Buildings will be as per NEC standard calculation method but I will explain design calculations as per NEC Optional calculation method only for the following NonDwelling buildings as permitted by NEC, Part IV. Optional Feeder and Service Load Calculations:

First: Lighting Loads
1 Lighting branch circuit ratings in nondwelling units
Lighting branch circuit ratings in nondwelling units may have one of the following ratings according to the type and application used as follows:
a) 15 and 20Ampere Branch Circuits
It shall be permitted to supply lighting units or other utilization equipment, or a combination of both.
b) 30Ampere Branch Circuits
It shall be permitted to supply fixed lighting units with heavyduty lampholders.
c) 40 and 50Ampere Branch Circuits
It shall be permitted to supply fixed lighting units with heavyduty lampholders.
2 Lighting load Calculations
In the broad sense, lighting loads for NonDwelling buildings may be categorized as follows:
 General lighting.
 Showwindow lighting.
 Track lighting.
 Sign and outline lighting.
 Other lighting.
2.1 General lighting
Definition:
General lighting outlets are those Outlets intended for
general use for fixedinplace luminaires (lighting fixtures). They are only
used for lighting for the normal use of the occupants and Its
intensity should be adequate for any type of work performed in the area.

Important!!!
The following Lighting fixtures are not included in General
Lighting category:

2.1.a Calculation Method
Determining the general lighting load as per NEC will be based on the load per area method as follows:
Step#1: determine the general lighting load density (in VA/ft2) for the building occupancy under design.
Rule#1: Applying
Table 220.12
The NEC code
introduces minimum general lighting loads (in VA/ft2) for various types
of buildings in Table 220.12.
Within the same
building, there are normally several different types of areas like storage,
office, hallways, and cafeterias, these areas must be considered separately
if their (VA/ft2) values are available in table 220.12.

Step#2: calculate the floor area in (ft2)
Rule#2: Applying
Table 220.12
The
floor area for each floor shall be calculated from the outside dimensions of
the building, or
other area involved.
The calculated floor area shall not include open porches,
garages, or unused or unfinished spaces not
adaptable for future use (like some attics, cellars, and crawl spaces).

Step#3: calculate the general lighting load
The general lighting load is calculated by multiplying the floor area in (ft2) of a building by its unit load (in VA/ft2) derived from table 220.12.
General lighting load in (VA) = Area of Occupancy in (ft2) X general lighting load density in (VA/ft2)
Step#4: Apply lighting demand factor from table 220.42 for type of building under design.
Important!!!
The demand factors of table 220.42
shall
not apply to the calculated load of feeders or services supplying areas in
hospitals, hotels, and motels where the entire lighting is likely to be
used at one time, as in operating rooms, ballrooms, or dining rooms.

Important!!!
For
the purpose of determining the circuit requirements, If the General Lighting
load is continuous (as in Most commercial structures), the calculated load is
multiplied by 1.25 (the inverse of 80%).

Rule#3: Calculating
Lighting Outlets load for
heavyduty Lampholders
As per NEC section 210.21, If there is Lighting
Outlets for heavyduty Lampholders in the NonDwelling Building, It shall be
calculated at a minimum of 600 voltamperes.

Example#1:
A 25,000 ft2 office building is being designed. What is the general lighting load and what load does the circuit need to supply?
Solution:
From Table 220.12, the unit load for an office building is 3.5 VA/ft2.
The general lighting load is determined by multiplying this value by the square footage of the building:
3.5 VA/ft2 x 25,000 ft2 = 87,500 VA
So, the general lighting load is 87,500 voltamperes.
However, the load is continuous and can only be 80% of the load supplied by the circuit. This value must be multiplied by 1.25 to determine the circuit requirements:
87,500 VA x 1.25 = 109,375 VA
The circuit is designed to supply 109.375 KVA
Notes for table 220.12
Important!!!
Don’t
apply the values of table 220.12 before reviewing the following notes:

Important!!!
The
general lighting load unit values specified in table 220.12 for guest rooms or guest
suites of hotels and motels
includes the following loads:
So,
no need to add the above outlets in load calculations per NEC method.

Important!!!
The
NEC method and table 220.12 are applied for any Additions to Existing
Installations for nondwelling installations.

Important!!!
Energy
saving–type calculations (which used to reduce the connected lighting load
and actual power consumption) are not permitted to be used to determine the
minimum calculated lighting load if they produce loads less than the load
calculated according to 220.12.

2.1.b Notes for NEC method for calculation of lighting branch circuit load
Important!!!
The
NEC doesn’t introduce a procedure for calculating the actual full load for
the individual lighting fixtures in a general lighting branch circuit.

Rule#4: NEC method for calculation of lighting
branch circuit load
If the required
information for calculating the actual full load for every individual
lighting fixture in the circuit is available, the following procedure will be
applied:

Important!!!
Actually,
The NEC method for calculation of lighting load is not required if the actual
full load for every individual lighting fixture in the circuit is determined.
Methods
for determining the actual full load for every individual lighting fixture in
the circuit is explained in our course and I recommend reviewing these
methods very well.

Rule#5: determining the actual load current of circuits
supplying lighting units that have ballasts, transformers, autotransformers, or
LED drivers
As per NEC Section
220.18 (b) states , circuits supplying lighting units that have ballasts,
transformers, autotransformers, or LED drivers, the calculated load shall be
based on the total ampere ratings of such units and not on the total watts of
the lamps.
This means that the
losses in light fixture switchgear (ballast, internal wiring, etc.) must be
taken into account when calculating the actual full load of light fixtures
and the current rating of the ballast, not the tube wattage, will be used.

Example#2:
A fluorescent lighting fixtures with 4 numbers 2 feet lamps, 18 watt/ lamp. Calculate the actual load for this lighting fixture.
Solution:
The actual total load of fixture = 4 lamps x 18 watt/lamp + losses
So, we can’t know the actual losses, we will use the same equation in another form
The actual total load of fixture = 4 ballast x watt/ballast = 4 x 20 w = 80 watt
2.2 Showwindow lighting
The calculation of this type of lighting is explained in Article " Branch Circuit Design Calculations – Part Four ".
2.3 Track lighting
The calculation of this type of lighting is explained in Article " Branch Circuit Design Calculations – Part Four ".
2.4 Sign and outline lighting
The calculation of this type of lighting is explained in Article " Branch Circuit Design Calculations – Part Five ".
2.5 Other lighting
Other lighting includes but not limited to the following:
 Security lighting,
 Parking area lighting,
 Sidewalk lighting,
 Roadway lighting,
 Stadium lighting,
 Tunnel Lighting.
2.5.a Rules applied for Calculation of Other lighting loads
Unfortunately, The NEC code don’t provide calculation rules for lighting types included under these additional lighting loads.
So, all additional lighting loads are calculated using the actual load designed by professional lighting programs and methods as explained in our course.
Important!!!
All
Additional
lighting loads should be computed separately from the general lighting load
and then added to the general lighting load.

Don’t
forget…
These additional
lighting loads are considered continuous loads where appropriate
and must be multiplied by 1.25 for feeder and overcurrent protection
calculations.

Rule#6: Calculating
the total lighting load for
buildings having more than one lighting category.
lighting loads for NonDwelling buildings may be
categorized as follows:
If more than one of the above lighting categories is
existing in the same building, Each lighting Category load is computed
separately and then combined to other lighting categories load to determine
the total lighting load.

In the next article, I will explain design calculations for Receptacle Loads for NonDwelling Buildings. Please, keep following.
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