electrical system illumination1tsy201314

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Electrical System



Ampacity of Conductors

- ability of wire or conductor to carry current

without overheating.

National Electrical Code ( NEC) provides that:

“ Conductor size and rating shall have sufficient

ampacity to carry load. They shall have adequate

mechanical strength and shall not be less thanthe rating of the branch circuit and not less than

the maximum load to be served”



Conductor Ampacity

- is determined by the maximum operating

temperature that its insulation can withstand

continuously without overheating



Example:

Size : 2 mm2 ( 14 AWG )

at 600C : Ampacity = 15 ampere

Type of insulation: T , TW

at 750C : Ampacity = 15 amperes

Type of insulation: RHW, THW, THWN

at 900C : Ampacity = 25 amperes

Type of insulation: SA, RHH , THHNat 1100C : Ampacity = 30 amperes

Type of insulation : AVA



Raceway

- Are channels or wiring accessories so design forholding wires, cables or busbars that are either madeof metal, plastic, or any insulating mediums.

Types for household wiring

1. The conduits

2. The connectors and other accessories

3. Conduit coupling, elbows and other fittings

4. Conduit supports, such as clamps, hanger5. Cable trays, cable bus, etc



Conduit

- conduit pipe is the most common electric

raceways used in all types of construction.

Classifications:

1. Metallic such as steel pipes, aluminum, etc

2. Non –metallic such as plastics



Outlet and Receptacles

Outlet - is any point that supplies an electric

load.

- usually consist of a small metal or non metal

box into which a raceway and or cable ends.

- refers only to the box itself



Different kinds of outlet

1. Convenience outlet or attachment cap

2. Lighting outlet

3. Receptacle outlet



Receptacles - are contact device installed at the

outlet fro the connection of a single

attachment plug.

A wall convenience receptacles is vertically

mounted between 30 to 45 centimeters above

the finished floor line.



Branch Circuit ( by NEC)

- the circuit conductors between the final over

current protective device and the outlets



Protection of the Branch Circuit

As a rule, branch circuit should be protected

from over current

NEC….. “ Conductors shall be protected against

over current in accordance with their

ampacities”



By definition,

Over Current is any current in excess of the

rated capacity of the equipment or rated

ampacity of the conductor.



Fuse , Breaker and Panel Board

Fuse - an over all current protected device with acircuit opening fusible element which openswhen there is an over current in the circuit.

- is a single pole , installed on a single wire thatcould only protect a single electric line.

- consist of a fusible link or wire that easilymelt at low temperature classified into two types:

1. Cartridge type - enclosed in an insulating fivertube

2. Plug Fuse type – enclosed in a porcelain cap



Circuit Breaker

-is an over-current protective device designed

to function as a switch.

- equipped with an automatic tripping device

to protect the branch circuit from overload

and ground fault.

- can be manually tripped ,,acts as circuit

switch.

- multiple pole, 1 , 2, or 3 poles



Panel Board

NEC …. A single panel or group of panel limits

designed for assembly in the from of a single

panel.

- known as panel or electrical panel

- simply a box wherein the protective

devices are grouped from which they are fed.

- Fuse Panel , Breaker Panel



Panel board with 100 cm high or less should be

located 135 cm from the floor to the center

line of the box.



Panel board with boxes over 100 cm high should

be located 75 cm from the floor to the bottom

of the box, except that the highest branch

circuit unit should not be more than 195 cmfrom the floor.



If necessary, the box maybe lowered to a

distance not less than 45 cm from the floor to

the bottom of the box. However, where a

maximum height of 195 cm above the floor tothe upper circuit or a distance of 45 cm above

the floor cannot be done, the panel should be

divided into two sections.



If two or more boxes are adjacent on the same

wall, they should be installed with the

horizontal center line of each box equidistance

from the floor. The center line distance of thehigher box controlling the boxes should be

installed with a minimum spacing of 10 com

apart.



Switchboard and Switchgear

- are free standing assemblies of switches, fuses

and circuit breakers that provide switching

and feeder protection to a number of circuits

connected to the main source.



FEEDER

NEC …… All circuit conductors between the

service equipment or the generator

switchboard of an isolated plant, and the final

branch circuit over current devices.



Location of Service Equipment

1. Should be centrally located to shorten all

home runs. Branch circuit run in excess of 30

meters will have an excessive voltage drop.

2. Accessible and convenient to approach

3. In residential houses, it is located near the

heaviest load center such as the kitchen and

laundry area.



Design of the Electrical System of Residential Building

( 1 storey and 2 storey)

Scale: 1 : 100 m ------ 1 cm - 1 m

1 : 50 m ------ 2 cm – 1 m

Lighting outlet shall be separated from the circuit of convenienceoutlet except in occupancies where the total connected load doesnot exceeds 15 amperes.

For ideal design, the maximum number of outlets per circuit = 12



Schedule of loads:

Method of Computation:A. Design Load Method

B. Area Method



Electrical Plan consist of the following:

• Floor Plan layout – Lighting

– Power

• Schedule of Loads

• Riser Single Line Diagram• Design Computations / Analysis

• Location Plan / Site Plan

• Legend

• Optionals: Details

•



Assignment:

Floor Area : 100 meters up to 150 meters

Draw a floor plans ( 3 identical )1 floor plan: label properly e.g rooms ,

dimension

2 and 3 floor plan: ?????????USE: small tracing paper, 1 inch margin in all

sides



DESIGN LOAD METHOD

100VA per L.O

200 VA per C.O.180 VA per CO

electrical system illumination1tsy201314

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