panel boards paper

8/10/2019 Panel Boards Paper

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PANELBOARDSA COMPLETE ANALYSIS

March 2nd, 2004

AREN 4570Professor Krarti

Jason Groob

Robert JohnsonRyan Kelley

Matthew Peters


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Panelboards Building Electrical Systems

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TABLE OF CONTENTS

EXECUTIVE SUMMARY .............................................................................. 1

ELECTRICAL DISTRIBUTION SYSTEMS.................................................... 1

PANELBOARD DEFINITION ........................................................................ 1

TYPICAL CONSTRUCTION ......................................................................... 2

PANELBOARD RATING AND IDENTIFICATION ......................................... 3

ENCLOSURES ............................................................................................. 5

CATEGORIES OF PANELBOARDS............................................................. 5

TYPES OF PANELBOARDS......................................................................... 5

TRANSFORMER / PANELBOARD CONNECTIONS.................................... 7

SAMPLE PANELBOARD DIMENSIONS AND DETAILS.............................. 8

GROUNDING.............................................................................................. 10

PANEL BOARD MANUFACTURERS ......................................................... 12

COST ANALYSIS........................................................................................ 12

CONCLUSIONS.......................................................................................... 13

REFERENCES............................................................................................ 14


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EXECUTIVE SUMMARY

Panelboards are the glue that holds the United States electrical system together. Neededto distribute electricity throughout a building, panelboards play a vital role in all electricalsystems. Panelboards house overcurrent protection devices to protect electric devices

from the dangerous short-circuit currents and consolidate general electrical systemcomponents. The manufacturing and installation of panelboards fills a substantialfinancial role in the lives of many Americans. To better understand panelboards, thefollowing report will include details on basic panelboard construction, various typespanelboards, and a cost analysis.

ELECTRICAL DISTRIBUTION SYSTEMS

Whether residential or commercial, distribution systems serve to distribute electricalpower throughout a building. Ranging in size and complexity, distribution systemsconsist of several key components, including overcurrent protection devices, meteringdevices, switches, conductors, and transformers. To better organize such systems,

panelboards are used to consolidate overcurrent devices, switches, and conductors.Common residential and commercial electrical system diagrams are shown in Figure 1.

Residential / Commercial Electrical Distribution SystemsFigure 1

PANELBOARD DEFINITION

The National Electric Code (NEC) defines a panelboard as a single panel or group ofpanel units designed for assembly in the form of a single panel; including buses,automatic overcurrent devices, and are equipped with or without switches for the controlof light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed inor against a wall or partition and accessible only from the front (Article 100-definitions).


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TYPICAL CONSTRUCTION

Although a wide variety of panelboards exists, most have a similar construction. Thebasic construction of a panelboard includes two main parts; the first is known as the canand the second is the interior. The can houses the interior components of the panelboardand allows the panelboard to be easily mounted to varying surfaces. The case is normally

constructed of galvanized steel. Figure 2shows the construction of a typical can.

Typical Can ConstructionFigure 2

The can of the panelboard also serves as the means for electrical system grounding. Allpanelboards should be grounded to protect the branch circuits and the people who use thepanelboard. As a general rule, grounding provides a path of low resistance in case of ashort circuit. The short-circuit current flows to the earth instead of through the metalcasing of the panelboard. In the case of uncontrolled short-circuit current, systemcomponents can be severely damaged. To ground panelboards, a direct connection fromthe can to a grounding bus is needed. To prevent potential damage, all NEC regulations

regarding grounding panelboards should be strictly followed. A diagram showing theconnection of the ground bus to a panelboard is shown in Figure 3.

Grounding Bus ConnectionFigure 3

The interior section of a panelboard consists of switches and various overcurrentprotection devices. Fuses and circuit breakers are the two types of overcurrent protectiondevices used in panelboards. The NEC limits the number of poles that can be used in onepanelboard to a maximum 42. A pole is defined as a connection of an overcurrentprotection device to one phase. For example, an overcurrent protection device that is


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connected to three phases will use three of the allowable poles. The overcurrentprotection devices are typically mounted directly to bus bars inside the panelboard. Ifany pole space is unused, it must be covered by either a filler plate or a spare protectiondevice. Figure 4shows the mounting of the interior to the can, Figure 5shows a detail ofthe interior, and Figure 6shows general panelboard connections.

Typical Interior Connection Detail of Interior Connection Figure 4 Figure 5

Panelboard ConnectionsFigure 6

PANELBOARD RATING AND IDENTIFICATION

Panelboards are rated by several characteristics. First, the panelboard type and systemtype (phase, wire, voltage) are listed. Next, because panelboards are designedspecifically for each particular installation, the necessary total amperage is shown.

With both maximum continuous amperes and available fault current known, the rating ofa panelboard can be found two ways. The first option, known as the full rating method, isto select circuit protection devices with individual ratings equal to or greater than theavailable fault current. The second option, known as the series rating method, is to selecta main upstream circuit protection device that has an interrupting rating equal to orgreater than the available fault current of the system. With this system, all subsequentdownstream circuit protection devices connected in series can be rated at lower values.

All loads must be displayed on the inside of the panelboard door, in the format of NEMAnumbering. Using such a format, the poles are separated into even and odd categories,


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enabling all circuits to be easily identified. On occasion, an additional listing of circuits,known as vertical numbering, is needed. Figure 7displays a sample of NEMA andvertical numbering.

Circuit NumberingFigure 7

To display the general panelboard ratings described above, a panelboard label isnecessary. Like the circuit numbering, the identification label is generally found on theinterior of the panelboard door. These labels provide important information about thesystem that may be necessary should a problem occur. A sample of a panelboard label isshown in Figure 8.

Sample Panelboard Identification LabelFigure 8


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ENCLOSURES

To ensure safety, NEMA has established guidelines for panelboard enclosures. Withseveral options available, the enclosure of the panelboard is often determined by theenvironment in which the panelboard will be installed. Listed below are severalexamples of panelboard enclosures, with brief descriptions of the exposed environment.

TYPE 1 General purpose indoor use.

TYPE 3R Outdoor use to provide a degree of protection against rain, sleet and external ice formation.

TYPE 4X Indoor and outdoor use to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose- directed water, and ice formation.

TYPE 3R/12 Indoor use to provide a degree of protection against circulating

dust, falling dirt, and dripping non-corrosive liquids.

CATEGORIES OF PANELBOARDS

Two different categories of panelboards have been created by the NEC: lighting &appliance and power. These categories are determined by the different types of branchcircuits connected to the panelboard. Both categories are shown below, with a briefdescription of system details.

Lighting & Appliance Panelboards - contain lighting equipment, appliances, receptacles, and other small loads.

Power Panelboards - consist of 10% or fewer of its branch circuits dedicated to lighting or appliances.

Defining characteristics of a lighting & appliance panelboard include that each phasemust be connected to the neutral bus and that the overcurrent protection devices must berated less than or equal to 30 A. In most cases, lighting and appliance panelboards aretypically found in residential applications.

Power panelboards are generally defined as those that do not fall under the lighting andappliance category. Differing from lighting and appliance panelboards, powerpanelboards are usually found in commercial buildings.

TYPES OF PANELBOARDS

There are two general types of panelboards, known as main breaker and main lug only. Inmain breaker panelboards, a breaker protects the entire panelboard. With a main lug onlypanelboard there is no breaker to protect the entire load. Figure 9 displays both types ofpanelboards.


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Types of PanelboardsFigure 9

Main Breaker Type Panelboards

The incoming supply cables are connected to the line side of the main breaker, feedingpower to the panelboard and branch circuits. The panelboard is disconnected from thesource by a main breaker, protecting the system from short circuits and system overloads.Commonly, the main breakers are bus connected to the main bus bars, providing higheroverall circuit integrity and avoiding overheating. Depending on panelboard orientation,the main breaker can be mounted horizontally or vertically. Figure 10 displays bothpossible orientations of the main breaker with respect to panelboards and branch circuits.

Main Breaker PanelboardsFigure 10


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Main Lug Only Type Panelboards

In the case of main lug only type panelboards, there is no main circuit breaker. Theincoming supply cables are connected directly to the bus bars and overload protection isnot provided. Generally, main lug only panelboards are used in special cases. Onecommon use is the addition of another panelboard next to an existing one because extra

poles are needed. In such a case, the main breaker provides adequate protection for theentire system, and the second, main lug only panelboard provides added space for branchcircuits. Figure 11displays two common connections between main breaker only andmain lug only type panelboards.

Main Breaker Only/ Main Lug Only ConnectionsFigure 11

TRANSFORMER / PANELBOARD CONNECTIONS

Panelboards receive power from a variety of sources, each with differences in voltage andcurrent. Generally, power is supplied by a utility power company at high voltages andcurrents. To step down voltages to the desired levels, local transformers are used at theresidential or commercial location. Several different types of step down connections thatare commonly used will be discussed.

13W SYSTEM As one of the most common distribution systems in use, thepanelboard operates at 120V (phase + neutral)and 240V (phase + phase). This systemis most commonly used in residential installations.

34W WYE-CONNECTED SYSTEM More common to commercial applications,the panelboard operates at 277V (phase +neutral)and 480V (phase + phase).

34W DELTA-CONNECTED SYSTEM Also more common to commercialapplications, the panelboard operates at 120V (phase, A or C + neutral), 208V (phase, B+ neutral), and 240V (phase +phase)

Figures 12-14compare the three systems described above.


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13W SYSTEMFigure 12

34W WYE-CONNECTED SYSTEM 34W DELTA-CONNECTED SYSTEM

Figure 13 Figure 14

SAMPLE PANELBOARD DIMENSIONS AND DETAILS

To better understand actual panelboard sizes and details, several Siemens brandpanelboards will be analyzed. Similar in construction and function, the following modelswill be compared and contrasted based on rating and size descriptions. The smallermodels, known as P1, SE, and S3 panelboards, all have field convertible mains andbottom or top feed options. Somewhat larger models, known as the S4/F1 and S5/F2,offer varying types of overcurrent protection with optional circuit breakers or fusibleswitches available.

P1 PANELBOARDS

P1 panelboards are the smallest of the product line offered by Siemens. The P1panelboard can support up to 42 1-pole branch circuits and are available to operate on12W, 13W, 33W, and 34W systems with voltages up to 480/277 VAC and 250VDC. Maximum current is 400 amps while short circuit interruption ratings are up to200,000 amps. Figure 15 shows both P1 panelboard dimensions and ratings.


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Siemens P1 Panelboard

Figure 15

SE PANELBOARDS

SE panelboards are comparable to P1 panelboards with several exceptions. The SEpanelboard can support up to 42 1-pole branch circuits and are available to operate on

12W, 13W, 33W, and 34W systems with voltages up to 600VAC and 250 VDC.Maximum current is 600 amps while short circuit interruption ratings are up to 200,000amps. Figure 16 shows both SE panelboard dimensions and ratings.

Siemens SE PanelboardFigure 16

S3 PANELBOARDS

S3 panelboards are the largest panelboard in this product line that Siemens offers. The S3panelboard can support up to 54 1-pole branch circuits and are available to operate on13W, 33W, and 34W systems with voltages up to 600VAC and 250 VDC.

Maximum current is 600 amps while short circuit interruption ratings are up to 200,000amps. Figure 17 shows both S3 panelboard dimensions and ratings.


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Siemens S3 PanelboardFigure 17

S4/F1 AND S5/F2 PANELBOARDS

Although similar in design and features, S4/F1 and S5/F2 power panelboards vary inavailable ratings. Both models will accept various circuit breakers and fusible switcheswith the S4/F1 panelboard allowing up to a 600 amp main circuit breaker and the S5/F2panelboard allowing up to a 1200 amp main circuit breaker. Figure 18 below listsavailable details of each panelboard model.

Siemens S4/F1 and S5/F2 PanelboardsFigure 18

GROUNDING

Grounding is one of the most important aspects of any electrical system. The NationalElectrical Code defines grounding as a conducting connection, whether intentional oraccidental, between an electrical circuit or equipment and the earth, or to someconducting body that serves in place of the earth.

There are two main objectives to grounding electrical equipment. The first objective is tokeep potential voltage differentials between different parts of a system at a minimum.


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PANEL BOARD MANUFACTURERS

There are several major manufacturers of panelboards in the US. Some of the largestsuppliers are as follows:

- Square D

-Kinney

- Murray- Westinghouse- Culter-Hammer- Siemens ITE- General Electric

The first four manufacturers listed provide mostly residential panelboards, while the lastthree cater more to the commercial sector.

COST ANALYSIS

Typical costs for residential panelboards are presented in Table 1 and commercialpanelboards presented in Table 2. Phase and total amperage differentiates between thetwo. In terms of overall estimates, residential panelboards will total between $850 and$1450 depending on the total amperage. Multiphase panelboards range from $910 to$6175 depending on total amperage, voltage, and the presence of a main breaker.

Table 1

Residential Panelboards

Ratings Cost

Voltage Ampere # Breakers Material Labor Subtotal Total w/ Profit

120/240V 100 10 $410 $265 $675 $850

120/240V 150 14 $645 $305 $950 $1,175

120/240V 200 18 $840 $350 $1,190 $1,450


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Table 2

Commercial Panelboards

Ratings Cost

Voltage Ampere # Breakers Main Breaker Material Labor Subtotal Total w/ Profit

3W 120/240V 100 10 NO $400 $315 $715 $910

3W 120/240V 100 14 NO $470 $360 $830 $1,0503W 120/240V 100 18 NO $510 $420 $930 $1,200

3W 120/240V 100 20 NO $575 $485 $1,060 $1,350

3W 120/240V 225 24 NO $655 $525 $1,180 $1,500

3W 120/240V 225 30 NO $760 $700 $1,460 $1,900

3W 120/240V 225 36 NO $870 $790 $1,660 $2,125

3W 120/240V 225 38 NO $935 $875 $1,810 $2,325

3W 120/240V 225 42 NO $980 $955 $1,935 $2,500

4W 120/208V 100 12 NO $450 $315 $765 $965

4W 120/208V 100 16 NO $520 $420 $940 $1,200

4W 120/208V 100 20 NO $605 $485 $1,090 $1,400

4W 120/208V 100 24 NO $660 $525 $1,185 $1,500

4W 120/208V 100 30 NO $760 $595 $1,355 $1,7254W 120/208V 225 32 NO $855 $700 $1,555 $2,000

4W 120/208V 225 34 NO $875 $750 $1,625 $2,100

4W 120/208V 225 36 NO $895 $790 $1,685 $2,150

4W 120/208V 225 42 NO $1,000 $925 $1,925 $2,475

4W 277/480V 100 12 NO $865 $360 $1,225 $1,475

3W 120/240V 100 20 NO $1,275 $525 $1,800 $2,175

3W 120/240V 225 24 NO $1,475 $700 $2,175 $2,675

3W 120/240V 225 30 NO $1,775 $790 $2,565 $3,125

3W 120/240V 225 36 NO $2,075 $875 $2,950 $3,575

3W 120/240V 100 12 YES $555 $395 $950 $1,200

3W 120/240V 100 20 YES $710 $525 $1,235 $1,550

3W 120/240V 225 30 YES $1,350 $925 $2,275 $2,8753W 120/240V 225 42 YES $1,575 $1,200 $2,775 $3,525

3W 120/240V 400 30 YES $1,875 $1,175 $3,050 $3,800

3W 120/240V 400 42 YES $2,100 $1,250 $3,350 $4,175

4W 120/208V 100 24 YES $830 $670 $1,500 $1,900

4W 120/208V 100 30 YES $935 $790 $1,725 $2,200

4W 120/208V 225 32 YES $1,575 $875 $2,450 $3,050

4W 120/208V 225 42 YES $1,725 $1,125 $2,850 $3,575

4W 120/208V 400 42 YES $2,350 $1,325 $3,675 $4,525

4W 120/208V 600 42 YES $3,475 $1,575 $5,050 $6,175

4W 277/480V 100 24 YES $1,700 $750 $2,450 $3,000

4W 277/480V 100 30 YES $2,000 $830 $2,830 $3,425

4W 277/480V 225 30 YES $2,525 $875 $3,400 $4,0754W 277/480V 225 42 YES $3,100 $1,125 $4,225 $5,100

CONCLUSIONS

Panelboards are an important part of any building electrical system. They serve as aplace to contain all of the overcurrent protection devices and organize the circuitry of thebuilding.


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REFERENCES

1. Square D. Square D.Oct. 2003. 28 Feb. 2004.

http://www.squared.com

2. Kinney Electrical Manufacturing Company. Kinney Electric.Jan. 2003. 28 Feb.2004.http://www.kinneyelectric.com

3.

Murray Electric System.Murray Electric System. Apr. 2000. 28 Feb. 2004http://www.murray-ky.net

4.

Siemens Power Panelboards. Siemens Power Panelboards. Jun. 2001. 28 Feb.2004

http://www.siemens.com/index/panelboards

5. Todays Westinghouse Electrical Company. Todays Westinghouse ElectricalCompany.Sep. 2003. 28 Feb. 2004http://www.westinghouse.com

6.

Means Building Construction Cost Data.R.S. Means Co. Kingston, MA. Oct.2003.

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