1. ELECTRICAL INSTRUMENTS ( service and utilization )
Class Instructor
Arch. / En.P.VINCENT J. DAYAG SR,MSArch.

2. ELECTRIC SERVICE Service is tapped on utility lines on agreeable point
Beyond property line
Connection may be on a pole with the following:
A. Overhead Service Drop ( OH )
B. Underground Service Lateral ( uG )
C. Underground Utility Line with Service Lateral ( ? )

3. CONDITIONS Length of service run Type of terrain Budget limitations
Utility company voltage
Site and nature of electric load
Local practices and ordinances
Maintenance and service continuity
Weather conditions
Importance of appearance
( urban design principles )

4. OVERHEAD SERVICE
Cost is cheaper by 10% - 50% compare to underground installation.
Bare – copper cable supported on porcelain glass insulators on crossarms for high voltage ( 2.4 KV plus )
Weatherproof Cable – secondary circuits at 600V below are run on porcelain spool of secondary racks

5. OVERHEAD SERVICE
Pre assembled Aerial Cable – three or four insulated cables wrapped together with metallic tape and suspended by hooks from the poles, used for 15 KV

6. UNDERGROUND WIRING Advantages Attractive Reliable Long life
Disadvantages
High cost
Three Types
Direct Burial
Pad Mounted
Slab

7. SERVICE EQUIPMENT
Transformers is required between high voltage incoming utility lines and secondary service conductors.
Necessary whenever voltage difference is significant.
Pole or Pad mounted outside the building.
Installed in room or outside the building.

8. TRANSFORMERS
Electrical device consisting of one coil of wire placed in close proximity to one or more other coils.
Used to couple two or more alternating-current (AC) circuits together by employing the induction between the coils.
Devices that transforms alternating current of one voltage to alternating current of another voltage.
A transformer in which the secondary voltage is higher than the primary is called a step-up transformer.
If the secondary voltage is less than the primary, the device is known as a step-down transformer.

9. TRANSFORMERS
Step Up – transformer rated 120V/480V transforms lower volt while 120V ac to 480V a-c bigger load.
Step Down – to transform bigger load to lower voltage.

10. TRANSFORMER Available in : 3- Phase Construction
Single Phase Construction
Power capacity is rated in kva
( kilovolt – amperes )
Single Phase Construction
Product of full load current and the voltage
100 kva will carry 2400/120v
I = W/v
Primary = 100,000va
120v = 41.6 A
Secondary =100,000va
120v = 832 A

11. SERVICE EQUIPMENT AND METERING
Provided at service point accessible to a meter reader.
Sub – units like apartments require sub- metering to discourage energy waste.
Multiple meters are accommodated.

12. SERVICE SWITCH
To disconnect all electric service , except emergency equipment ,in case of fire.
Accessibility is important, near service conductor point.
Comprise of six properly rated switches assembled in a switchboard.

13. PRIMARY TO SECONDARY CONNECTION
Lighting Arrester – to protect electric equipment from damage caused by lighting or other high voltage currents, using spark gaps to carry current to the ground without passing to the device.

14. UTIILIZATION
Circuit Breakers – switch that interrupts an electric circuit to prevent excess current from damaging the apparatus that causes fire.
Ground Fault Interrupter –a circuit breaker that senses currents caused by ground faults and instantaneously shut off power before damage or injury can occur.
Cartridge Fuse – fuse having a one time or renewable fusible link enclosed in an insulating fiber tube.
Knife Blade Fuse – fuse with metal blade at each end for making contact with fusible link.

15. UTILIZATION
Junction Box – enclosure or housing and protecting electric wires and cables that are joined together in connecting and branching circuits.
Knife Switch – form of air switch which a hinged copper plate is placed between two contact clips.
Three- Way Switch – a single pole, double switch used in conjunction with another to control lights from two locations.
Four Way Switch – switch used in conjunction with two three – way switches to control lights from three locations.

16. UTILIZATION
Branch Circuits are portions of electrical system extending from final over current device protecting the circuit to the outlets served by the circuits.
Each branch must carry a load amount according
About 20% is reserved for expansion, flexibility and safety and should not exceed 30M in length.
General Purpose Circuits supply a current to a number of outlets for lighting and appliances

17. UTILIZATION
Appliance Circuits supply current to one or more outlets specifically intended for appliances.
Individual Circuits supply current only to single piece of electrical equipment.
Other Circuits – a separate wiring are required for the following :
Telephone
Cable TV
Intercom
Fire Alarm System

18. ELECTRICAL PLAN Lighting Outlet Lay Out Power Outlet Lay Out
Special Outlet Lay Out
Load Schedules
Riser Diagram
Electrical Notes
Legends
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