Database Design for Electrical Panels - Maesc.org

Christian Brothers University
650 East Parkway South
Memphis, TN 38104-5581
Database Design for Electrical Panels
By
Shalini Gupta,
Monte DePouw
John Ventura
MEMPHIS AREA ENGINEERING AND SCIENCES CONFERENCE
MAY 10, 2002

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Database Design for Electrical Panels
By Shalini Gupta, Monte DePouw, and John Ventura
Abstract
Electrical engineers specify the design for electrical panels. The panels could be a
lighting panel, receptacle panel, or a main panel. Currently most engineering firms
perform all calculations associated with the design of electrical panels without the benefit
of computer software. This is an inefficient and time-consuming method. Although, there
is software available; most companies have not adopted them due to the fact that they are
not compatible with their existing software and they are not user friendly. The purpose of
this project is to design a computer program, which calculates the components for the
electrical panel.
Based on the goals and available resources, the following needs metric matrix has
been generated:
Needs
Research
User Interface
Ease of Use
Compatibility
Compliance with NEC
Testing
Table 1: Need-Metric Matrix
Description
Extensive Research is required in order to perform a good design
The User Interface needs to be visually pleasing
The database should be easy to follow and use
As the database is being designed in Ms Access, it needs to be
compatible with different versions of Ms Access available
All calculations performed need to be compliant with the
equations and rules stated in the NEC handbook.
The design will have to be tested on a regular basis to ensure the
accuracy of its commands and functions

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In view of the needs matrix, the database chosen for the design of the electrical
panel is Microsoft Access due to the following reasons:
• User friendly
• Graphical Interface
• Single Screen display
• Easy to update the database
• Less prone to error
• Saves time
• Compatible with different platforms.
This paper explains the fundamentals of panel design and the software design
implementation.

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Table of Contents:
Introduction…………………………………………………………………………… 1
Database Fundamentals ……………………………………………………………... 3
Inputs and Outputs of the Automated Panel………………………………………… 8
Calculation of circuit Breaker size…………………………………………………… 12
Recommendations ……………………………………………………………………. 14
Conclusion…………………………………………………………………………….. 15
Appendix ……………………………………………………………………………… 16
Bibliography ………………………………………………………………………….. 18

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Introduction:
The purpose of this project is to design a computer program in Microsoft Access
to calculate breaker sizes and the load totals on each phase for electrical panels in a
friendly graphical user interface for the sponsor DePouw Engineering, LLC. Many of the
repetitive tasks in the computing panel schedules have been automated. DePouw
Engineering is an electrical consulting firm located in Memphis, Tennessee. DePouw
Engineering specializes in commercial and industrial power distribution and lighting
system design. A typical project design includes point-by-point calculation; short circuit
analysis, protective device coordination, and wire size correction for ambient
temperature, conduit fill, and voltage drop analysis. The firm currently employees three
registered electrical engineers, two designers, and a support staff. A licensed master
electrician is employed to inspect all projects at critical stages of construction, as well as
to verify compliance with plans and specifications from start to finish.
DePouw Engineering has a wide range of customers-architects, engineers, schools
and sports center. The Production Manager’s concern at the firm is that the phase loads,
diversification of phase loads, calculation of breaker sizes and cascading of panels to a
main panel are done by hand (Note: All these calculations are performed on paper and the
final product is called a panel schedule). This is time consuming, inefficient and prone to
error.
As supported by IEEE Industrial Applications, (Volume 37- Issues 3, 1),
calculations for panel design performed by a computer tend to make the complex and
time consuming task of looking up tables and calculating circuit breaker ratings easier
and less prone to error. Some companies have designed databases to perform

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calculations for panel design, however, most electrical design companies have not
adopted these programs as they are not visually appealing, or because they do not
approve of the parameters used for the calculations, as the equations are based on a
different version of the National Electrical Code (NEC) handbook. Hence, the
production manager at DePouw engineering would like a database custom-designed for
their needs and in accordance with the code specified in the NEC version adopted by the
state of Tennessee. The program will display an interface, which an electrical engineer
can use to enter data and receive the final automated panel schedule. The computer
generated panel schedules will then be plotted by the engineer and submitted to the
contractor.
Microsoft Access was chosen to design the database. This is due to the fact that
the company already has a copy of the software and the employers are more comfortable
implementing the panel design in MS Access.

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Database Fundamentals:
It can be overwhelming when large amount of data needs to be tracked in project
organization. Several companies still use a paper filing system, text documents or
spreadsheets to keep track of information. This kind of record keeping can be tedious,
inefficient, and requires a lot of physical space. A more convenient data management
systems namely a database has been developed. One of the best examples of this new
software is Microsoft Access.
Below is the explanation of the main fundamental components of Access that
were employed in the design of the program.
Tables
A table is a collection of data about a specific topic, such as products or suppliers
(Using Visual Basic 6, 453). The tables in Access are analogous to that of Excel. Below
is an example of the table where data was entered for the load type.
Figure1: Load Type table used in the program

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These tables were used to extract data for the pull down menu in the main form.
Separate tables were used for each drop-down menu. Using a separate table for each topic
means that the data is stored only once, which makes the database more efficient, and
reduces data entry error.
Forms
In Access, users friendly forms can be created that allow the user to enter information in
the graphical interface. These forms can be custom designed for the user. The
information entered in the graphical form has information that is transparently passed
onto the user (Microsoft Access 200 Bible, 785). The figure below represents the forms
that were created.
Figure2: Form View of the three-phase form

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The tabular like region (containing the circuit number, the load type, description,
Phase A, Phase B, etc….) is called a sub form. A sub form is a form within a main form.
Below is the display of the single-phase form.
Figure3: Form View of the single-phase form
Note that the difference between a three phase and a single-phase form is the
number of columns. In the three-phase form there is an extra column-Phase C. In
addition, separate calculations have been programmed in the two forms for the
calculation of the breaker sizes. The user can interchange between the two forms by
changing the option Phase (on the top part of the screen) between single phase and three
phases.

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Visual Basic Codes
Once the user has completed entering the necessary input, Access performs the
calculations. The code for these calculations was programmed using Visual Basic, which
is an inbuilt feature in Access.
Below is a sample code. This code changes the display of the sub- form from a
single-phase form to a three-phase form depending on the selection made.
Figure 4: Visual basic code for changing a sub-form
The change of the sub form is able to take place because of the event procedure
triggered by the combo box (Using Visual Basic 6, 855). (Note: In access the drop down
menu is called the combo box. Here the combo box being referred to is the drop down
menu titled Phase in the top half of Figure1 and Figure 2). The Phase combo box is
shown below.

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Figure 5: Phase Combo Box
It can be observed in Figure 5 that the Visual Basic subroutine will be
triggered after the user enters a value in the Phase combo –box, or if the user
makes a selection from the drop down menu.

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Inputs and Outputs to the Automated Panel Form:
The panel design program outputs the breaker sizes and the totals of the load on each
phase. The inputs and outputs are presented in Table 2:
Input
Output
Voltage
Breaker Size
Phase
Breaker Size
Wire Size
Main Circuit Breaker/Lugs
Panel Type
New/Existing
AIC
Bus
Mounting
Entry Feeder
Load Type
Pole
Breaker Size
Load on the Phase
Breaker Size
Table2: Program inputs and outputs
The main inputs, which affect the computation of breaker size, are the values for
the voltage, phase, the number of poles, and the load on the phase. The other standard
inputs such as the wire size, main circuit breaker/lugs, panel types, new/existing, AIC,
bus, mounting, entry feeder, load type do not affect the calculations.
Once all the data has been entered the program automatically calculates the
breaker size and the total of the load on each phase.

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Explanation of Inputs:
The first input is voltage. Voltage plays a very important role in the calculation of
the circuit breaker. The voltages can be chosen from a pull down menu in the database
form or the user can enter the voltage. The voltages that have been programmed into the
database that can be selected from a drop down menu are shown in Table 3. The reason
that these values were programmed into the database is because these are the most
commonly used at DePouw Engineering.
Voltage
120
120/208
120/240
240
277/480
480
Table 3: Voltage programmed into the drop-down menu in the database
The next input is Phase. The user can select from the pull down menus either a
single phase or a three-phase voltage supply. This input affects the circuit breaker
calculations. The number of wires constitutes the next input. The number of wires can be
either two, three or four. The number of wire indicates the number of hot wires (in
addition to indicating a neutral and a ground wire). The Main CB/lugs input implies
whether lugs will be used or the size of the circuit breakers that will be used. The sizes of
the main circuit breaker that have been programmed into the database are as follows:
20A, 25A, 30A, 40A, 45A, 50A, 60A, 70A, 80A, 90A, 100A, 110A, 125A, 150A, 175A,

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200A, 225A, 250A, 300A, 400A, 600A, 800A and 1000A. These values were obtained
from the NEC 1999. The next input is Panel Type. The Panel type gives an overall
description of the panel. The following description of the panel types can be selected
from the pull down menu in the database: critical, emergency equipment, isolated ground
bus, life safety, normal, and UL listed for Non-linear. Next, the user can specify whether
the pane is new or existing. In addition, the user can enter the panel name in the dialog
box in the access database form.
Further, the user can input the values for the Amperage of Interrupted Circuit
(AIC). The AIC values that have been programmed in are 22000,30,000,42000,65000,
and series rated. The user can select from a pull down menu the ampacity of the bus. The
values programmed for the amperage of the bus are: 60A, 100A, 125A.175A, 225A,
400A, 600A and 800 A. These values are the standard values specified by NEC 1999. In
addition, the user can enter the mounting of the panel board. The drops down menu
options for mounting are: flush, surface and switchboard. Subsequently, the user can
enter the entry of the panel: that is top, bottom, left and right.
For each circuit (in the sub form), the user can select whether it is a one-pole,
two–pole or a three-pole breaker. The user can also enter the panel description and select
the load type for each circuit. Within the load types pull down, there are many different
choices. These choices have been abbreviated in the program; the full form and the
description of these choices can be found in the Table 4.

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Abbreviation
BL
BSP
C
Description
BL stands for Blank, It is used to place blank values in the selected
circuit group
This acronym stands for Bussed Space
C stands for Continuous load
D
GFI
H
H/M
K
R
SR
T
WH
X
This implies that the load type for the circuit group is Dwelling
(such as residential units)
H stands for hospital load
This abbreviation indicates a hotel of motel load.
K stands for Kitchen load
R sets the load type for the circuit group to Receptacle
SR implies that the current circuit is a Spare.
T sets the load type for the circuit group to Transformer.
The acronym WH stands for the load type Warehouse
X stands for X-ray load
XH XH indicates that the load type for the current circuit group is X-
Ray Equipment at Health Care Facilities.
Table 4: Description of the abbreviation of the load-type options in the Access form.

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Calculation of Circuit Breaker size:
Depending on whether the user selects a 1- pole, 2- pole or a 3-pole circuit
breaker the calculation for the circuit breaker varies.
If a 1-pole circuit is chosen then, the calculation for the 1-pole circuit breaker is as
follows:
1-pole CB size =
SVA
80%*(
P − N)
V
(Equation 1)
and, if a 2-pole circuit is chosen then the calculation for the 2-pole circuit is as follows:
2- pole - CB size =
SVA
80% *( P − P)
V
(Equation 2)
Finally, is a 3 pole circuit is chosen then the calculation for the 3-pole circuit is as
follows:
3-pole-CB size =
SVA
3 *80%*( P − P)
V
(Equation 3)
Where SVA
(P-N) V
(P-P) V
CB
= Specified Volt-Ampere (that is the load entered by the user)
= Line to Neutral voltage
= Line to Line voltage
= Circuit Breaker
It can be observed that each of the three equations above have been divided by
80%. This is because according to NEC-1999, Article 210-20: “ A branch circuit that
supplies continuous load or any combination of continuous load and non-continuous load,
the rating of the over current device shall not be less than non-continuous load plus 125
percent of the continuous load. The 125 percent is equivalent to
1
”.
80%

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Article 240-6 of the NEC-1999 specifies that the standard ampere ratings for fuses
and inverse time circuit breakers shall be considered as follows: 15, 20, 25, 30, 35,
40,45,50,60,70,80,90,100,110,125,150,175,200,225,250,300,350,400,450,500,600,700,80
0,1000,1200,1600,2000,2500,3000,4000,5000, and 6000 amperes. Based on this, the
breaker sizes calculated from the above three equations are rounded of to the nearest
standard ampere rating.

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Recommendations
The automated Panel Schedule in Microsoft Access is definitely more user
friendly than the paper based design method. The database is efficient as it saves the user
time and is an error free method. This program calculates the breaker size for each
circuit and the total of load on each phase. The calculations in this program are the basis
of the design of a panel schedule. Once the basic calculations are performed then the
design engineer usually performs the diversification of phase loads and cascading of
panels to a main panel. This is also being currently being done manually at DePouw
Engineering. Hence, the next step would be to use this program and program additional
features that will perform the diversification of the phase loads and cascading of panels to
a main panel. Thus, this program would serve as the backbone for the new program.
Since the company already has Microsoft Access, it would be advisable to continue the
program in Access as it does not incur any additional cost and the users are already
familiar with the software.

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Conclusions:
The Access program presents an excellent solution (to the tedious task of
designing a panel schedule. The automated schedule is user friendly, has a visually
pleasing graphical interface, error-free, saves time, and is compatible with different
platforms.
The program written has been tested, and all calculations agree with those
performed manually. Moreover, the calculations are now performed faster and more
accurately. In addition, all the information can be edited and stored for future reference.
Overall, this program is useful, so design engineers will use it. The final automated panel
schedules created using this program will be plotted and submitted to the contractor.

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References
National Electrical Code 1999. Massachusetts: National Fire Protection Incorporated,
1998.
Sutherland R.G. A standard system for power format studies.
Pruchniaki, Wayne. Peasley, Richard. &Reselman,Bob. Using Visual Basic 6. New
Delhi: Prentice Hall of India, 1999.
Prague, Cary. Irwin, Michael. & Reardon, Jennifer. Microsoft Access 200 Bible
.California: IDG books, 1999.