How to Empower the future of UX Design with Gen AI
Electrical Load Estimation Course
1.
2013
Electrical Load Estimation Course
Ali Hassan
Certified Energy Manager – AEE ‐ USA
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About Author
Hi, I'm Ali Hassan el‐Ashmawy, I began my career from 1999
as a site electrical engineer then as area manager from 2001
then as electrical designer from 2003 then as senior
electrical designer from 2006 and up to date.
In my past experience, I designed and construct about 100
projects in different countries like Egypt, Kuwait, Indonesia, KSA, Gabon and Iraq.
My designs were approved by many international authorities like USA corps of
engineers and USA ministry of exterior – OBO Office.
I'm certified energy manger CEM from AEE – USA since 2006 and I hope to become a
well‐known designer in the field of electrical design.
To contact me please email to Ali1973hassan@yahoo.com
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Table of Contents
Page
S/N Item
No.
1 Introduction 5
2 Importance of Electrical Load Estimation (Preliminary Load 5
Calculations)
3 Definition of Important terms in Load Estimation 5
3.1 Connected load 5
3.2 Demand load 5
3.3 Demand Interval 6
3.4 Maximum demand 6
3.5 Demand factor (in IEC, Factor of maximum utilization ku) 6
3.6 Coincidence factor (in IEC, Factor of simultaneity ks) 7
3.7 Diversity factor 10
3.7.1 Difference between demand and diversity factor 11
3.8 Load factor 18
4 Methods of Electrical load estimation 19
5 Preliminary Electrical Load estimate 19
5.1 Difference between preliminary and final load estimate 19
5.2 Preliminary load calculations sub‐methods 20
5.3 Space‐by‐Space Method (functional area method) 21
5.3.1 Usage conditions of Space‐by‐Space Method 21
5.3.2 Area Measurement in space by space method 21
5.3.3 Method of estimation by using Space‐by‐Space Method 21
First Case 21
Second case 25
5.4 The Building Method 29
5.4.1 Comparison between space‐by‐space and building methods 29
5.4.2 Usage conditions of Building Method 29
5.4.3 Area Measurement in Building Method 29
5.4.4 Method of estimation by using Building Method 29
First Case 30
Second case 31
5.5 Area method 35
5.5.1 Usage conditions of Area Method 35
5.5.2 Method of estimation by using Area Method 36
First: basic method 36
Second: Optional Method (Load centers method) 38
5.6 General notes for all methods of electrical load estimations 41
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1‐ Introduction
At the beginning of the project, in the draft design (early design) stage, the electrical
design professional should do the following:
• Make Analysis of load characteristics,
• Review The available voltage system types/classes and levels,
• Review the utility’s rate structure,
• Make roughly a key single‐line diagram and a set of subsidiary single‐line
diagrams. The key single‐line diagram should show the sources of power e.g.
generators, utility intakes, the main switchboard and the interconnections to
the subsidiary or secondary switchboards.
• Develop Demand factor relationship between connected loads and the actual
demand imposed on the system.
2‐ Importance of Electrical Load Estimation (Preliminary Load Calculations)
Electrical Load Estimation is very important in the draft design (early design) stage
because it help to:
• Plan the connection to upstream network and MV circuit configurations.
• Plan the transformers substation(s) (if any) and the main switchgear room.
• Apply to Power Company for supply.
• Calculate initial budget for the electrical works.
3‐ Definition of Important terms in Load Estimation:
There are many important terms which must be understood before performing the
load estimation, these terms are:
3.1 Connected load
It is the Sum of all the loads connected to the electrical system, usually expressed in
watts.
3.2 Demand load
It is the electric load at the receiving terminals averaged over a specified demand
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Table#1: Factor of simultaneity (ks) for Apartments Block
From Table#1 in above, it is possible to determine the magnitude of currents in
different sections of the common main feeder supplying all floors.
For vertical rising mains fed at ground level, the cross‐sectional area of the
conductors can evidently be progressively reduced from the lower floors towards the
upper floors. These changes of conductor size are conventionally spaced by at least
3‐floor intervals.
2‐ Calculation of apparent power
From Table#1, since the number of downstream consumers = 25, the Factor of
simultaneity ks = 0.46
So, the apparent‐power supply required for the building = 150 KVA x 0.46 = 69 kVA
3‐ Calculation of The main service size
The current entering the rising main at ground level (main service size) = (150 x 0.46
x 1000) / (400 x √3) = 100 A
4‐ Calculation of The third level service size
The current entering the third floor (the third level service size) = sum of currents
delivered to third and fourth floors
The number of consumers in the third and fourth floors = 4 + 6 =10 consumers
From Table#1, for number of downstream consumers = 10, the Factor of
simultaneity ks = 0.63
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Workshop A:
• 4 nos. lathe with 5 KVA each,
• 2 nos. pedestal drill with 2 KVA each,
• 5 nos. sockets outlets 10/16 A on one circuit with 18 KVA total,
• 30 nos. fluorescent lamps on one circuit with 3 KVA total.
Workshop B:
• One nos. Compressor with 15 KVA,
• 3 nos. sockets outlets 10/16 A on one circuit with 10.6 KVA total,
• 10 nos. fluorescent lamps on one circuit with 1 KVA total.
Workshop C:
• 2 nos. ventilation fans with 2.5 KVA each,
• 2 nos. Oven with 15 KVA each,
• 5 nos. sockets outlets 10/16 A on one circuit with 18 KVA total,
• 20 nos. fluorescent lamps on one circuit with 2 KVA total.
• Draw a key single line diagram for this building?
• Determine both the demand (utilization) factor and simultaneity factor with
the help of tables # 2 & 3 in below?
• Calculate the demand load for each level in the key single line diagram?
Table#2: Factor of simultaneity for distribution boards (IEC 60439)
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Step#1: List all the loads in each workshop and write the apparent power of each
load in KVA beside it.
Step#2: write the utilization factor for each load, IEC gives Ku estimation values for
these loads as follows:
• For motor Ku = 0.8
• For socket outlets Ku = 1 (depend on the type of appliances being supplied
from the sockets concerned)
• For light circuits Ku= 1
The Table of Calculation for Steps# 1&2 will be as follows:
Apparent
Apparent Utilization
Workshop Power
Load Type Load No. Power Factor
Name Demand
(KVA) Max.
Max.KVA
lathe No.1 5 0.8 4
No.2 5 0.8 4
No.3 5 0.8 4
Workshop No.4 5 0.8 4
A: pedestal drill No.1 2 0.8 1.6
No.2 2 0.8 1.6
5 nos. sockets outlets 10/16 A 18 1 18
30 nos. fluorescent lamps 3 1 3
Compressor 15 0.8 12
3 nos. sockets
Workshop
outlets 10/16 A
10.6 1 10.6
B:
10 nos. fluorescent
lamps
1 1 1
ventilation fan No.1 2.5 1 2.5
No.2 2.5 1 2.5
Workshop Oven No.1 15 1 15
C: No.2 15 1 15
5 nos. sockets outlets 10/16 A 18 1 18
20 nos. fluorescent lamps 2 1 2
Step#3: calculate the Max. Demand apparent power in KVA for each load = apparent
power X Ku for each load.
Step# 4: group same type of loads on one distribution panel/box and this will be the
first Level of distribution (LEVEL 1).
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hop C: 1 8
No. 2.5 1 2.5
2
Oven No. 15 1 15
1
No. 15 1 15
2
5 nos. sockets outlets 18 1 18 0.28 5
10/16 A
20 nos. fluorescent 2 1 2 1 2
lamps
3.8 Load factor
The load factor is the ratio of the average load over a designated period of time,
usually 1 year, to the maximum load occurring in that period.
Load factor = Average load / Maximum load
Free download
You can download tables for different factors listed above by clicking the following
links:
• IEEE Demand Factor Values
• Unified Facilities Criteria ‐UFC‐ Demand Factor Values
• NEC Demand Factor Values
• Demand Factor Values From Other Regulations
• Diversity Factor Values
• Unified Facilities Criteria ‐UFC‐Load Factor Values
• IEC Factor of Simultaneity Values
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4‐ Methods of Electrical load estimation
There are (5) methods for Electrical Load Estimation, which are:
A‐ Preliminary load calculation
This method is subdivided into (3) sub‐methods as follows:
1. Space by space (functional area method),
2. Building method.
3. Area method.
B‐ NEC load calculations.
C‐ Final load calculations.
Note:
In this course, I will explain the preliminary load estimation methods, and the two
other methods; NEC load calculations and Final load calculations will be explained
later in course " EE‐3: Basic Electrical design course – Level II ”, because the
preliminary load estimation methods are used in the early design phase while the
other two methods are applied in the final stages of design.
5‐ Preliminary Electrical Load estimate
5.1 Difference between preliminary and final load estimate
before going through the calculation steps for Preliminary Electrical Loads, we need
to highlight the main differences between the load estimation or calculation by the
preliminary and final methods. The following table shows these differences as
follows:
S/N Preliminary load calculations Final load calculations
1 Units of Loads will be in (W/ft2) Units of Loads will be in KW (kilo‐watt),
watts per square foot or/and or/and KVA (kilo‐volt‐ampere), or/and HP
(VA/ft2) volt‐amperes per square (horse power)
foot
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2 units are used interchangeably Units can’t used interchangeably. So, Hp
because unity power factor is will be converted to kVA; and kVA may be
assumed multiplied by the estimated power factor
to obtain kW if required
3 Unity power factor is assumed Different values of power factors
according to load types.
4 Demand and load factors values Demand and load factors values are Real
will be selected from tables values that will document and reflect the
based on the designer estimation number, the type, the duty rating
and they will be Used to (continuous, intermittent, periodic, short
calculate the transformer and time, and varying), and the wattage or
service size. volt‐ampere rating of equipment supplied
by a common source of power, and the
diversity of operation of equipment
served by the common source.
5 The connected load will be Actual demand load will be calculated
estimated based on area or based on summation of individual
population building connected loads modified by
suitable demand and diversity factors
6 Easy and Fast calculations economical, cost effective calculations
insuring that items of equipment and
materials are adequate to serve existing,
new, and future load demands
5.2 Preliminary load calculations sub‐methods:
As I indicated before, this method is subdivided into (3) sub‐methods as follows:
1. Space by space (functional area method),
2. Building method.
3. Area method.
Note:
A particular design may use one Preliminary load estimate method or a combination
from two or even the three methods.
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