E4 Electrical Installation

#1 Power Distribution

Electrical Distribution

200,000 – 400,000 Volts

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

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

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

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

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Underground Service Transformer

Thick Rubber Gloves Transformer 7200v Primary 120/240v Secondary © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2

Eye Protection Rubber Arm Shields

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Electric Meter

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

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Meter Enclosure

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

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Residential Single Phase Power

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

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Common Residential 120/240v 1Ø

L1 L2 N 240v 120v 120v

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

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Electric Panel

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

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Good Workmanship Counts Cable ties Smooth bends in the wires © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2

Main Breaker Neutral Ground

Typical 1Ø Electric Panel

Circuit Breakers Bus Bars

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

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