electrical system for high rise building

8/16/2019 Electrical System for High Rise Building

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ELECTRICAL SYSTEM DESIGN for HIGH-RISEBUILDING

These buildings distinctively difer rom industrialbuildings or manuacturing with regards to electric utilizationequipment installed and the number o oors. The latter are

mostly single or two-storey structure due to operationalrequirements and constraints. Exceptions are the taller silos orstocpiling o materials or !nished products.

" hotels # condominiums or their combinations. Thede!nitions as to number o oors and areas vary romone party to another.

" commercial establishments

" general o$ces

%igh & rise buildings normally reer to occupancy or'


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(. )eneral *ighting + ,ower

1 – HIGH RISE BUILDING POWER SUPPLY REQUIREMENTS:

"sewage eectors

"pumps # drainage

"water sprinle !re suppression/

"potable and non-potable water supply

0. 1ater ,umps

"conveyors2 dumbwaiters2 others

"elevators and escalators

3. Transport 4ystem

"heaters or humidity control

"blowers and ans ventilation"air-conditioning or temperature control

2. %eating2 5entilation + 6ir-conditioning %567/ 4ystem

" power or appliances and o$ce machines

" light or general illumination2 seeing tass2decorative eatures2 hallways and stairways2others


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8. 7ommunication 4ystem

9ote' The latter items could be integrated into the building automatio system as may be provided in the design.

" noise masing and acoustics2 others

" sound reinorcement and video acilities" bacground music and paging

" !re suppression and alarm system

" intrusion and hold-up control system

:. 6uxiliaries

" Terminals" 7,; and peripherals

oors" ?ntercom

" ,6@A telephone system


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2 – HIGH-RISE BUILDING SYSTEM COMPONENTS

6 high-rise building electrical system is composed ohundreds o components2 designed and assembled into a safe,functional power-delivery system. ?n !gure B.( shows a typicalbuilding electrical system riser diagram2 where the buildingCselectrical system is connected to the utility system. %ere2 it is a

pad-mounted transormer2 but in other cases it might be a bano transormers mounted overhead on a utility pole or a demandless than (2DDD 56/.

The underground service connects the utility system tobuildingCs main distribution panel MDP/. *ocated within the MDP is the main building over-current device2 or main disconnect2 aswell as individual over-current devices or the systemcomponents connected to the MDP. The MDP may also containprovisions or utility metering2 as well as instrumentation or themeasurement o system voltage and current.


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The main disconnect device can be either a circuit breaeror a used switch. This main device oten contains specialcircuitry or sensing low-level aults i.e. ground aults or morethan (2DDD 6mp main/2 which otherwise might escape detection. The MDP might be thought o as the electrical nerve center othe building. ?t is normally located near building exterior walland as close as possible to the utility transormer to minimizethe cost o main service eeders.

Thus2 all components o the system must be chosencareully based on design requirements and must unction saely2

under normal operating conditions and also under abnormalconditions2 such as short circuits.


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3 – POWER SUPPLY SYSTEM

The ranchise utility power company serves at nominallevel o B3D#((8-volt2 single- or three-phase2 two-2 three or ourwires depending on the type o load and as long as it does notexceed (2DDD 56. or extremely large service entrance current2multiple conductors may be used. *iewise2 multiple

protective#disconnect devices not exceeding six =/ may beconnected in parallel or the service entrance as stated byP.E.C.).

The size o the load center depends on the proposedconnected load and allowances or uture growth o theestablishmentF its con!guration2 on the other hand2 depends onthe requirements and available acilities o the utility company.

or establishment o greater than (2DDD 56 load2 asmost commercial and industrial consumers2 the power companyrequires a load center unit sub-station and serves power atprimary line distribution level o (3.: or 30.8 5olts or whatever

potential level available in the vicinity.


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The maor components o the load center are'

;sually in large installations with private load centers2 the

practice is to use BD:#(BD-volt or general lighting and power2and 0=D-volt or motors. This appears to be the more economicaland practical arrangements.

3.1 – U!"!#!$% &o"'%(

or lighting and appliances2 0=D-volt line can liewise beused but availability o !xtures or such potential may not beeasily procured2 i.e. B=8-volt ballasts or uorescent andconvenience outlet with built-in unit transormers o 8D to (DD

562 0=D-B3D#((8-volt ratings.

Three-phase electric motors are normally dual-voltage2i.e. 0=D#B3D volts and using the higher 0=D-volt rating will resultin hal-as-much ampere draw2 hence smaller wires2 lower circuit

breaer rating although higher voltage/ and smaller starter unit.

0/ Getering equipment

3/ *ow-voltage switchgearF secondary side

B/ ,ower transormer section

(/ %igh-voltage switchgearF primary side


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or total load o (2DDD 56 or less2 the power supply isBD:#(BD-volt or B3D#((8-volt only. ?n some cases2 and ortemporary construction power2 the power company would serve0=D-volt or use o construction equipment2 subect to their

requirements2 rules and regulations.

4hould the customer enterprise be required to provideits own load center unit substation2 several options are

available2 again subect to approval o the power utilitycompany.

3.2 – Co$)%*r'!o$ of Lo'+C($(r,


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OPTION – 1 : %igh-voltage supply line rom power companytransormed to utilization voltage o BD:#(BD-volt or general

lighting and power2 and 0=D-volt or motors using twoseparate power transormers as shown in !g. 3.Ba/.


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HPTION – 2 : %igh-voltage supply line rom power companytransormed to 0=D-voltsF general lighting and powered by the 0=D-volt line

through a unit dry-type transormer2 0=D-BD: # (BD-volt2

asshown in !g. 3.Bb/.


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HPTION – 3 : 4imilar to Hption & B IexceptJ several units o smallerunits o

smaller dry-type transormers are distributed in theareas or

oors or general lighting and power systemF these unittransormers are ed by 0=D-volt line or lines rom theload

center as shown in !g 3.B c/.


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6ny o these con!gurations will serve the purpose otransorming the incoming high-voltage line rom the utilitycompany to acceptable utilization equipment level. The !nal

choice o the desired system is normally dictated by costs andequipment availability. ,ower transormers are either dry-type or

oil-immersed.

1hile a Iail-saeJ system could not be adopted due to itsprohibitive cost2 still some degree o exibility and reliability othe system can be reasonably reached.

3.3 – Lo'+ C($(r "(!/!"!0 R("!'/!"!0

The load center can be split into two B/ equal oridentical units to serve the liewise equally2 as ar as practicable2divided electrical loads. ?n cases o ailure o any o the maorcomponents o either unit2 the remaining hal is still operational.4ystem selectivity can be attained2 either on the primary or

secondary sides or both2 by using Itie-breaerJ.

The common disadvantage o all o the above loadcenter con!gurations is its inexibility. ?n cases o breadown oany o the main components2 i.e. high or low-voltage switchgearmains2 or the transormer itsel will result in total system shut-

down.


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,roperly coordinated interlocing system shouldbe provided between the tie and main breaers toprevent accidents.

The load centers described in the proceedingparagraph will be served on two B/ separate ends andthus termed Idouble-endedJ unit. 7ustomarily2 thepower company serves this type o load center romtwo B/ separate distribution eeder lines to urtherenhance the systemCs selectivity. igure 3.3 shows the

one line diagram o a typical Idouble-endedJ system asadopted rom Hption 3. The same can be done or bothHption ( and B.


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9ote' The interloc2 mechanical#electrical2 will prevent puttingIH9J the tie-breaer until either o the main breaer isIHJF metering 7TCs and ,TCs are to be installed in both

the high-voltage incoming lines ( and B.

The power requirements o the building can besu$ciently supplied by the power company at acceptable level2continuity and characteristics. There are2 however2 instanceswhen the power may be interrupted due to the system ault orde!ciencies2 some o which are inherent in the powertransmission and distribution. *onger interruptions will greatlyinconvenience the building occupants and may even bedangerous to lie and limbs. *osses in terms o unproductive man-

hours and business opportunity may also substantial.

– EMERGENCY POWER SYSTEM

The suggested solution2 other than the sel-containedbattery-powered emergency lights2 is a stand-by diesel engine-generator set or sets. ?t is not economically sound2 and probablypoor engineering practice2 to provide (DDK bac-up or stand-bypower because o the tremendous costs o the generator set orsets to be used in relatively short time o main power

interruptions.


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The more essential loads o the building are to be suppliedwith emergency power in cases o main power ailure. 9ormally2

these are the ollowing'

,ower transer to stand-by generator can be donemanually by double-throw transer-switch or automatically byautomatic-transer-switch ATS/. or the latter2 it is necessary thatthe eeder#s or line#s serving the essential loads should notinclude the non-essential acilities. 4eparate emergency lines andpanel boards will be provided exclusively or the purpose. 6typical one-line diagram is shown in !g. 0.( as adopted rom !g.3.3.

" 4tairwaysC and hallwaysC lighting or saety purposes

" Looms or suites o top executives

" 7omputer system

" Hne or two elevators to be used by physically handicapped

" 1ater pumps and !re pumps

" 7ounter areas or public transactions


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The system operates as ollows'

5oltage level and time setting as mentioned may beadusted to the desired level o the user2 but instant transerrom main to stand-by power is not possible since it will requiresometime or the generator voltage to build-up.

" The ATS could also be programmed to automaticallyIexerciseJ or operate the generator at no-load or (8-minute2 twice-a-wee periods in order to eep the setand auxiliaries in good running conditions.

" 1hen main power is restored to its rated level2 theATS instantly transer the load bac to the main

power eederF ater ( or B minutes o main powerstabilized conditions2 the generator set automaticallystopsF

" 1hen main power voltage dips to


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or uninterruptible power supply as may be required bycomputerhardwares and the lie2 a diferent equipment con!guration isnecessary. ?t

is discussed in the succeeding paragraphs.7omputer hardwares and operations requires controlled

environment as to temperature2 humidity and dust or satisactoryperormance.The same is true or its electric power supply.

Po(r S*44"0 for Co54*(r S0,(5

Hn power interruptions2 the time-lag or the emergencygenerator to build-up and supply power through the 6T4 is a waybeyond the recovery time o the computer. %ence2 the computerwill shut-down2 will have to be reset and re-started. ? the computeris on a long-batch run schedules2 it may be necessary to re-runthe batch viz. program/ rom the start. There is also the possible

errors and damages to the computer hardwares and sotwareswhich may prove very costly.

,ower hits and dips which is normal occurrences in 67power system are sometimes beyond the tolerable limits o the

computer. 4ome hardwares can not tolerate power disturbance omore than (#8 o a cycle o the normal =D %z power. 1hile speciallydesigned automatic-voltage-regulators 65L/ may serve thepurpose2 the problem will be in the response time to correct theabnormalities2 not to mention actual power interruptions.


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The recommended conditioned power system or computer isthe

Iuninterruptible power supplyJ system or ;,4. ?n the country most;,4 are

static type. 6 typical bloc diagram is show in !g. 0.B.


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The recti!er-charger2 ed rom emergency eeder thruIL7@J breaer2 supplies the >-7 bus. The battery is charged andat the same time supplies power to the inverter where >-7 poweris inverter to 6-7 output or the computer load. 7harging o the

battery is appropriately controlled.

" 1hen power is interrupted2 the oating battery will supply>-7 bus such that the inverter will not sufer any powerstoppageF the battery ban is normally rated to supply

power or (D to (8 minutes2 time enough to build-up and puton the line the emergency generator. The battery bancomposed o (DD to (8D industrial type-heavy duty units2each with a rated terminal voltage o B to B M 5olts or higher

capacity units.

" %its and dips will not be reected in the 6-7 output lines asthis is absorbed in the recti!er # charger onlyF the ;,4 inefect2 !lters the power to the computer.

?n cases o power supply and system in!rmities'

The output eeder line to the computer is protected bythe inverter circuit breaer I?7@J.


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There are several supplies o imported and locally

manuactured ;,4 who can assists the users in selecting thecon!guration most suited to their respective purposes. 4everaloptions o Ledundancy eatures are available to enhance thereliability o the system.

" 1hen the ;,4 itsel ails2 the static-transer switch I44J will

automatically transer the output to the by-pass lineF thetranser is o the mae-beore-brea operation that the 6-7output will not detect the switch madeF Ganual transer tothe by-pass line can also be made thru the commercialcircuit breaer I77@J.

6 rotary type combination o an 6-7 motor-driven-alternator and stand-by diesel engine prime mover withIywheelJ is another con!guration o a ;,4 system as shown in

!g. 0.32 this is sometimes termed as Idynamic ;,4J system. Theywheel stores and supplies the rotating power i.e. ineticenergy/ or the alternator beore the stand-by prime moverassumes the 6-7 motor drive unctions in cases o power ailure. This is similar with the principle o rotating regulators inmaintaining the speed o a >-7 generator.


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8 – EEDER : NUMBER SI6ES

eeder line can either be bus way bus bar truning/

or insulated conductors or combination o both. The ormer ismore versatile2 neat in appearance but decidedly moreexpensive @us ways are very popular especially or highampere capacity lines. ?t can carry up to


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8.( – Co$,!+(r'!o$ !$ 7( D(,!%$ of ((+(r, '$+Pro(8!o$,

" 1hile a single eeder may su$ciently supply severalareas or oors or loads2 so the scope o it afects in caseso breadown.

" The same principle could be adopted or airconditioning2 elevators2 pumps and other motor loads

" The idea is to minimize areas afected by a singleeeder breadownF

and so orthF i the oor is su$cientlylarge2 it may even be divided into zones

and ed rom diferent eeders.

eeder ??? - to serve =th2 :th2 (Dth N

eeder ?? - to serve @asement2 Bnd2 0theeder ? - to serve )round2 3rd2 8th oors

"(!/!"!0

" or the general lighting and power system o a high-rise building2 some designer distribute the loads amongseveral eeders2 example'


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Co$9($!($"0 A9'!"'/"( S!#(, of B*, '0, orCo$+*8or,

" 6 set o eeder breaers2 say (D units o (2DDD

6mperes each2 another set o (D units o 8DD ampereseach and so orth will require lesser number oreplacement units in stocs as compared againstnumerous eeders o substantially diferent sizes obreaers.

M!$!5!#(+ N*5/(r of R(4"'8(5($ Br('(r, !$ So8 oR(+*8( I$9($or0 C'rr0!$% Co,,

" 1hile multiple bus ways or conductors can be used to

meet desired current-carrying capacity o the line2 thereshould be some limit to this multiplicity or practicalpurposes in handling and where building spaces arerestricted.

for example2 three or more sets o large sizedconductors can not be conveniently terminated ina single receiving or originating lugs or breaerterminal.


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A""o'/"( &o"'%( Dro4, !$ 7( Co$+*8or,

" or motors2 owing to its starting current andoccasional overload runs2 the sizes shall be computedas ollows.

" branch circuit wires or lighting2 heating2 and similarloads should have a capacity o not less than (B8K othe load supplied with over current protection not

exceeding the capacity o the conductors or (8DK o therating o the loadF it is considered good engineeringpractice i the capacity o the conductor is not less than(8DK o the load supplied.

9ote' The sizes o eeder and branch circuit wiresare based on the connected load2 allowances or

uture growth2 demand actor and diversityactors. The following can be used as referencefor this purpose:

" or branch circuits the allowable voltage drop notexceeding 3K at the arthest outlet o power2 heatingand lighting loads. 1hile or both feeder and branchcircuits to the arthest outlet the allowable voltage dropnot exceeding 8K to provide reasonable e$ciency ooperation.


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S!$%"( 5oor "o'+

;se' 3 - (B8 mmO or B8D MCM THW 7u wire P BB86mp capacity in =8 mm Q or B M inch Q rigid metalconduit RMC/

Size of conductor R (B8K o (:D 6 R BB8 6

Example: 6 (8D hp2 3-phase 00D-5olt squirrel cage induction mot with auto-transormer starter and ull load ampere draw

(:D 6mp.

" (8D to BDDK or bigger motors with reducevoltage2 wye-delta or autotransormer starters.

" B8D to 3DDK or smaller motors2 less than < M hpwith ull-voltage or across-the &line starters.

6pproximately it will be'

1here the multiplier MK value depends on the type or class omotor as well as the starter or controller to be used2

Size of circuit breaker protection R MK times motor ull-

load ampere

Size of conductor R (B8K o motor ull-load ampere *6/


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Size of circuit breaker R (8DK o (:D 6 R B


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Size of conductor R (B8K ull-load ampere o highest ratedmotor plus ull load current o other loads/x demandactor

1here computed load exceeds the maximumavailable wire size2 multiple or parallel runs can be used.

5oltage drops should also be computed todetermine the propriety o the selected size o conductorsF

9ote' 3B8 mmO


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Size of circuit breaker protection R highest motor breaerrating plus

ull-load ampere o other loads/ x demandactor

?deally2 load centers and panel boards should be locatedon the center o the loads to be served to save on wire runs and tominimize line voltage drops. %owever most o the time thedesigning architect2 or aesthetic purposes2 has the !nal decisionon the matter.

= – LOAD CENTER; PANEL BOARDS or SWITCHGEARS

The size o eeder conductor should be maintainedthrough-out. ?t should not be reduced2 say at point IxJ regardlesso the reduced current beyond the said point-o-tap. 4uch

reduction in conductor size may be allowed i appropriately sizedbreaer is installed to serve as protection or the reduced line. The exception are or runs not exceeding B8 eet and within sight2provided that the reduce line capacity is not less than (#3 o themain run capacity.

;se' 8DD 6T2 =DD 62 3,2 8DD5 ACBR 003 6mperes

R S3DD6 B< (0 =8 B


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The electrical engineer should2 however2 strive to locate the panelboards at point where the arthest load to be served is within 3Dmeters. Htherwise2 larger sized wires may be necessary to

compensate or the voltage drop.

,anel board mounting o motor starter units may also be involv

b/ ,ower distribution panels

a/ *ighting + appliance panels

They are generally classi!ed into two categories'

6 panel board consists o a metal enclosure containingbus bars to which circuit breaers or used switches areattached. The interior space o the housing provides su$cientphysical space or sae installation o the circuit conductors totheir respective over current devices see !g. =.(/.

?n general panel boards and switchgear are used ascontrol protection points or groups o eeder or branch circuitsserving the elctrical loads in building area2 usually a oor or a

section o the oor.

P'$(" /o'r+,; S!87/o'r+, S!87%('r,


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6 switchboard switchgear, on the other hand areree standing assemblies o switches2 uses and circuitbreaers2 which serve as locations or larger over currentdevices2 or as main distribution panels or an entire building.

4witchboards are physically larger than panel boards2 due tothe size o the over current devices involved2 and are design toprovide the necessary space or installation o larger cablessee !g. =.B/.

c/ 7ubicle with number o compartments less than thatrequired or

metal-clad or compartmented switchgear2 usually havingpartition.

b/ 7ompartmented with one or more non-metallic partitions/

a/ Getal-cladHther types o metal-enclosed switchgear are'

Gain metal-enclosed switchgear or commercial2industrial2 and public buildings is invariably located in thebasement2 and housed in a separate well-ventilated electricalswitchgear rooms.

There is no clear distinction made between theterms IswitchboardJ and IswitchgearJ2 although oten high-voltage equipment above =DD 5olts/ is reerred to asswitchgear. 1hen molded case circuit breaers are utilized in aswitchboard it is oten nown as building type switchboard.


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etermine rom other designers the exact electricalrating o all equipment2 viz! HVAC2 plumbing elevators andescalators2 itchen and othersF the electrical designer may beased or comparative characteristics o these equipment asregards the electrical supply.

7onsult the local company as regards the point oservice entrance2 service voltage2 metering equipment andother requirements or power connectionsF the same should bedone or the telephone system.


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>etermine the location and estimated sizes o the diferentelectric supply equipment such as load center2 switchboards2electrical panel board2 rooms or enclosuresF this will enable the

architect to allocate spaces or these equipment. This estimatedspace requirements could be checed and adusted as may benecessary ater the completion o the detailed plans.

6ssign circuitry or all lighting and power system to

appropriate panels including emergency lines2 and compute panelloads.

>esign the lighting system2 using either the lumens orpoint-by-point methods2 ater due consultation with the architectand lighting designer as to the type o luminaires2 ceiling and wall

!nished. or clarity o the plans2 the lighting design which ismostly a reection o the ceiling is separate rom those o powerlayout showing the oor plans. 6 separate sets o plans may beprepared or auxiliaries2 viz. !re alarm2 hold-up and burglar2paging and bacground music2 noise masing and the lie.


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7hec and coordinate with other trades2 architecturalstructural2 5672 mechanical2 plumbing2 others to minimizeconicts in the wor execution.

,repare riser or one line diagram to include maindistribution panels2 load centers2 switchboards or switchgearsand other service equipment. 7ompute eeder2 sub-eeder sizesand all protective equipment ratings.

the latter may belong to the proect management team or theconstruction manager/


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T'/"( – 1: T04!8'" Mo"+(+ C',( C!r8*! Br('(r r'5( S!#(,;Tr!4

S(!$%, '$+ I$(rr*4!$% R'!$%FRAME SIZE TRIP SETTING

50 Amp 15 20 25 30 35 40 45 50100 Amp 15 20 25 30 35 40 45 50

60 70 80 90 100

250 Amp 70 80 90 100 110 125 150175 200 225

400 Amp and 600 Amp 125 150 175 200 225 250300 350 400 450 500 600

800 Amp and 1200 Amp 250 300 350 400 450 500600 700 800 1000 1200

1600 Amp 400 450 500 600 700 800

1000 1200 16003000 Amp 2000 2500 3000

4000 Amp 4000

5000 Amp 5000

6000 Amp 6000


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T04!8'" I$(rr*4!$% R'!$%


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S'$+'r+ A54(r( R'!$%, for Lo &o"'%( *,(,

0 # 600 Amp 15 40 80 150 300

20 45 90 175 350

25 50 100 200 400

30 60 110 225 500

35 70 125 250 600

0 # 600 Amp

601 1200 2000 4500

650 1350 2500 5000

700 1500 3000 6000

800 1600 3500 1000 1800 4000


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" >istribution 4witchgear 7onstruction2 ,erormance24election

+ ?nstallation/ @y ' L. 1. @lower

" ,hilippine Electrical 7ode part ? + ??/

@y ' ?nstitute o ?ntegrated Electrical Engrs. H the ,hils.?nc.

" >esign + 6nalysis o @uilding Electrical 4ystems @y ' V.%. Gathews

" Electrical 1iring 7ommercial & based rom 9E7 =th ed/

@y ' L.*. 4mith + 4.*. %erman

L e e r e n c e s '

electrical system for high rise building

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