1.  E4 Electrical Installation #1 Power Distribution

2.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 2 Electrical Distribution 200,000 – 400,000 Volts Substation Transformers Drop Voltage To 7200 Volts 7200 Volts 208/480 Volts Three Phase (3Ø) 120/240 Volts Single Phase (1Ø) Transformer Drops Voltage Transformer Drops Voltage

3.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 3 Power at the Pole A step-down transformer mounted to a pole can provide normal voltage directly to a building close to the pole When the building is far from the pole, the high voltage is run underground to a transformer near the building

4.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 4 Line Voltage 7200 Volts Ground Fuse 7200 Volts underground to transformer at House #2 7200v Primary 120/240v underground to electric panel in House #1 Tap for 7200v 1 Pole, 2 Houses, 2 Transformer Types 120/240v Secondary out of transformer

5.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 5 Transformers Following is a picture of an underground service transformer –The transformer is stepping down 7200 volts to 120/240 volts –Take note of the safety precautions practiced by the power company technician

6.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 6 Underground Service Transformer Transformer 7200v Primary 120/240v Secondary Rubber Arm Shields Thick Rubber Gloves Eye Protection

7.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 7 Electric Meter Meter hub on a residence

8.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 8 Electric Meter Meter Enclosure Power In Power out to electric panel

9.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 9 Residential Single Phase Power Following is a diagram of 120/240 volt 1Ø power

10.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 10 L1L2N 240v 120v Common Residential 120/240v-1Ø

11.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 11 Electric Panel Inside the building is the electric panel Circuit breakers distribute the power

12.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 12 Good Workmanship Counts Smooth bends in the wires Typical 1Ø Electric Panel Cable ties Main Breaker Neutral Ground Circuit Breakers Bus Bars

13.  © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 13