chapter 04 - the branch circuit

8/11/2019 Chapter 04 - The Branch Circuit

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THE BRANCH CIRCUITTHE BRANCH CIRCUITbyby

EngrEngr. Alexis T.. Alexis T. BelonioBelonio

Department of Agricultural Engineering andDepartment of Agricultural Engineering andEnvironmental ManagementEnvironmental Management

College of AgricultureCollege of Agriculture

Central Philippine UniversityCentral Philippine UniversityIloilo CityIloilo City

[email protected]@yahoo.com


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IntroductionIntroduction

Electric CircuitElectric Circuit It is the complete pathIt is the complete path

traversed by an electric current.traversed by an electric current. Branch CircuitBranch Circuit As defined by NEC it is theAs defined by NEC it is the

circuit conductors between the final ever currentcircuit conductors between the final ever current

protective device and the outlets. It is the onlyprotective device and the outlets. It is the onlywiring installed between the circuit over currentwiring installed between the circuit over current

protective device, I.e. the fuse or circuit breakerprotective device, I.e. the fuse or circuit breaker

and the outletsand the outlets


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The Branch CircuitThe Branch Circuit


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Factors to Consider inFactors to Consider in

Designing Branch CircuitDesigning Branch Circuit FlexibilityFlexibilitycan accommodate all probablecan accommodate all probable

pattern, arrangement, and possible expansion.pattern, arrangement, and possible expansion.

ReliabilityReliabilitycontinuous service and supply ofcontinuous service and supply of

powerpower SafetySafetycan provide double emergency powercan provide double emergency power

EconomyEconomyrefers to initial and operating costrefers to initial and operating cost

Energy ConsiderationEnergy Considerationenergy conservationenergy conservation

technique, control, etc.technique, control, etc.

Space AllocationSpace Allocationeasy maintenance,easy maintenance,expandability, etc.expandability, etc.


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ClassificationsClassifications General purpose branch circuitGeneral purpose branch circuit

supplies outlets for lighting andsupplies outlets for lighting andappliances, including convenience outlet.appliances, including convenience outlet.

Appliance branch circuitAppliance branch circuit suppliessupplies

outlets intended for feeding appliances.outlets intended for feeding appliances.

Individual branch circuitIndividual branch circuit supplies asupplies a

single specific item.single specific item.


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Circuiting Guidelines BasedCircuiting Guidelines Based

on NECon NEC The Code requires sufficient circuitry to supplyThe Code requires sufficient circuitry to supply

residential load of 30 watts per square meter inresidential load of 30 watts per square meter inbuildings excluding porches, garages andbuildings excluding porches, garages and

basement.basement.

The requirement of 30 watts per square meterThe requirement of 30 watts per square meter

works out to 80 square meter per 20 ampereworks out to 80 square meter per 20 ampere

circuit (2,400 watts) or 60 square meters for 15circuit (2,400 watts) or 60 square meters for 15ampere circuit (1,800 watts)ampere circuit (1,800 watts)


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Good practice suggest that a load should notGood practice suggest that a load should notexceed 1,600 watts for 20 ampere circuit orexceed 1,600 watts for 20 ampere circuit or

1200 watts for a 15 ampere circuit. Thus.1200 watts for a 15 ampere circuit. Thus.

Observe a maximum load of 1,200 watts on aObserve a maximum load of 1,200 watts on a

15 ampere circuit with maximum are of 4015 ampere circuit with maximum are of 40

square meterssquare meters A maximum load of 1,600 watts on a 20A maximum load of 1,600 watts on a 20

ampere circuit with a maximum area of 53ampere circuit with a maximum area of 53

square meters.square meters.


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The code requires a minimum of 20 ampereThe code requires a minimum of 20 ampereappliance branch circuit to feed all smallappliance branch circuit to feed all small

appliance outlets in the kitchen, pantry, diningappliance outlets in the kitchen, pantry, dining

and family room.and family room. The general purpose branch circuit shall beThe general purpose branch circuit shall be

rated at 20 amp circuit wire with NO. 12 AWGrated at 20 amp circuit wire with NO. 12 AWG

being the minimum size of conductor wire forbeing the minimum size of conductor wire for

all convenience outlet.all convenience outlet.

Circuit load on a 15Circuit load on a 15--ampere circuit shall beampere circuit shall belimited to values given below.limited to values given below.


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Branch Circuit CapacityBranch Circuit Capacity Electric HeatElectric Heat

Circuit BreakerCircuit Breaker

SizeSizeMaximum WattsMaximum Watts

@120 volts@120 voltsMaximum WattsMaximum Watts

@@

240 volts240 volts15 amp15 amp 14401440 28802880

20 amp20 amp 19201920 38403840

30 amp30 amp 28802880 57605760


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Branch Circuit RequirementsBranch Circuit Requirements15 amp15 amp 20 amp20 amp 30 amp30 amp 40 amp40 amp 50 amp50 amp

Max. size ofMax. size of

conductorconductorNo.14No.14 1212 1010 88 66

Minimum size tapsMinimum size taps No.14No.14 1414 1414 1212 1212

Over current deviceOver current device

ratingrating15 amp15 amp 2020 3030 4040 5050

Lamp holderLamp holder

permittedpermitted

AnyAny

typetype

AnyAny

typetype

H. dutyH. duty H. dutyH. duty H. DutyH. Duty

Receptacle ratingReceptacle rating

permittedpermitted15 amp15 amp 15 to15 to

20203030 40 to40 to

50505050

Maximum loadMaximum load 15 amp15 amp 2020 3030 4040 5050


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Plug outlets or convenience receptacle shall bePlug outlets or convenience receptacle shall be

counted in computing the load if it is not includedcounted in computing the load if it is not includedin the load for general lighting circuit. Thus, toin the load for general lighting circuit. Thus, tofind the number of outlets for a 9 and 12 amperefind the number of outlets for a 9 and 12 ampere

loading on 15 amp and 20 amp respectively.loading on 15 amp and 20 amp respectively. For 15 ampere circuit: 9/1.5 = 6 outletsFor 15 ampere circuit: 9/1.5 = 6 outlets

For 20 ampere circuit: 12/1.5 = 8 outletsFor 20 ampere circuit: 12/1.5 = 8 outlets

Convenience receptacle shall be plannedConvenience receptacle shall be plannedproperly so that in case of failure by one of theproperly so that in case of failure by one of the

circuit, the entire area will not be deprived ofcircuit, the entire area will not be deprived ofpower supply. In terms of reliability of service,power supply. In terms of reliability of service,each area shall be provided alternately with theeach area shall be provided alternately with thedifferent circuits.different circuits.


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All kitchen outlets shall be fed from at least twoAll kitchen outlets shall be fed from at least twoof these circuits.of these circuits.

The code further stipulates that, all receptaclesThe code further stipulates that, all receptacles

are potential appliance outlet and at least twoare potential appliance outlet and at least twocircuits shall be supplied to serve them.circuits shall be supplied to serve them.

Certain outlets in the room shall be designatedCertain outlets in the room shall be designatedas appliance outlets such as:as appliance outlets such as:

All kitchen receptaclesAll kitchen receptacles

Dining room receptaclesDining room receptacles

One of the living roomOne of the living room


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The Code requires that, at least one 20The Code requires that, at least one 20ampereampere--circuit supply the laundry outlets.circuit supply the laundry outlets.

If air conditioner is anticipated, provide aIf air conditioner is anticipated, provide aseparate circuit for this appliance.separate circuit for this appliance.


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Other Good Practices inOther Good Practices in

CircuitingCircuiting Lighting and receptacles should not beLighting and receptacles should not be

combined on a single circuit.combined on a single circuit. Do not connect all building lighting on a singleDo not connect all building lighting on a single

circuit.circuit.

Lighting and receptacles shall be supplied withLighting and receptacles shall be supplied withcurrent from at least two circuits so that if acurrent from at least two circuits so that if asingle line is out, the entire are is not deprived ofsingle line is out, the entire are is not deprived of

powerpower Do not allow combination switch and receptacleDo not allow combination switch and receptacle

outlet.outlet.


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Provide at least one receptacle in the bathroomProvide at least one receptacle in the bathroomand one outside the house. Both must beand one outside the house. Both must beGround Fault Circuit Interrupter type.Ground Fault Circuit Interrupter type.

Provide switch control for closet lights. PullProvide switch control for closet lights. Pull

chain switch is a nuisance.chain switch is a nuisance.

Convenience outlet though counted as part ofConvenience outlet though counted as part ofthe general lighting load shall be limited to 6the general lighting load shall be limited to 6

convenience outlet on a 15 ampere circuit and 8convenience outlet on a 15 ampere circuit and 8convenience outlet on a 20 ampere circuit.convenience outlet on a 20 ampere circuit.


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The Code requires that at least one 20 ampereThe Code requires that at least one 20 ampere

circuit supply shall be installed to the laundrycircuit supply shall be installed to the laundryoutlets.outlets.

Convenience outlet shall be laid out in such aConvenience outlet shall be laid out in such a

manner that no point on a wall is more than 2manner that no point on a wall is more than 2meters from an outlet. Use a grounding typemeters from an outlet. Use a grounding type

receptacles only.receptacles only.


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Protection of the Branch CircuitProtection of the Branch Circuit

All branch circuit should be protected from overAll branch circuit should be protected from over

current.current. Over current protection device opens the circuitOver current protection device opens the circuit

when the current rating capacity of thewhen the current rating capacity of the

equipment being protected is exceeded.equipment being protected is exceeded. Over current protection device is alwaysOver current protection device is always

connected at its hot line end to the voltageconnected at its hot line end to the voltage

source as its load end to the circuit wiring.source as its load end to the circuit wiring.

F i f O


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Functions of Over currentFunctions of Over current

Protection DeviceProtection Device To protect wiringTo protect wiring

To protect transformerTo protect transformer To protect lightTo protect light

To protect appliances and otherTo protect appliances and otherequipmentequipment

O C P iO C t P t ti


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Over Current ProtectionOver Current Protection

DevicesDevices FuseFuseis an overall currentis an overall current

protection device with a circuitprotection device with a circuitopening fusible element whichopening fusible element whichopens when there is an overopens when there is an overcurrent in the circuit.current in the circuit.

Circuit BreakerCircuit Breakeris an overis an overcurrent protective devicecurrent protective device

designed to function as adesigned to function as aswitch. It is equipped withswitch. It is equipped withautomatic tripping device toautomatic tripping device toprotect the branch circuit fromprotect the branch circuit fromoverload and ground fault.overload and ground fault.


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Panel BoardPanel Boardis ais a

single panel or groupsingle panel or grouppanel limits designedpanel limits designed

for assembly in formfor assembly in form

of a single panel. It isof a single panel. It iscommonly known ascommonly known as

electrical panels. Itelectrical panels. It

includes buses,includes buses,automatic overautomatic over

current protectivecurrent protective

device with or withoutdevice with or without

switches for theswitches for the

control of light, heatcontrol of light, heat

or power circuits.or power circuits.


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ReferencesReferences

FajardoFajardo, M.B. and L., M.B. and L. FajardoFajardo. 1994.. 1994.

Electrical Layout and Estimate. SecondElectrical Layout and Estimate. SecondEdition.5183 Merchandizing, Manila,Edition.5183 Merchandizing, Manila,

Philippines. 336pp.Philippines. 336pp.


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Thank you very much andThank you very much andGod Bless!!!God Bless!!!

chapter 04 - the branch circuit

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