E 4 Electrical Installation 1 Power Distribution Electrical

E 4 Electrical Installation #1 Power Distribution

Electrical Distribution 200, 000 – 400, 000 Volts 208/480 Volts Three Phase (3Ø) 7200 Volts Transformer Drops Voltage 7200 Volts Substation Transformers Drop Voltage To 7200 Volts 120/240 Volts Single Phase (1Ø) © 2005 Refrigeration Training Services - E 4#1 Power Distribution, Delta & Wye Systems v 1. 2 2

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 - E 4#1 Power Distribution, Delta & Wye Systems v 1. 2 3

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

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 - E 4#1 Power Distribution, Delta & Wye Systems v 1. 2 5

Underground Service Transformer Eye Protection Rubber Arm Shields Thick Rubber Gloves Transformer 7200 v Primary 120/240 v Secondary © 2005 Refrigeration Training Services - E 4#1 Power Distribution, Delta & Wye Systems v 1. 2 6

Electric Meter • Meter hub on a residence © 2005 Refrigeration Training Services -

Meter Enclosure Power In Electric Meter Power out to electric panel © 2005 Refrigeration

Residential Single Phase Power • Following is a diagram of 120/240 volt 1Ø power

Common Residential 120/240 v-1Ø L 1 L 2 240 v N 120 v ©

Electric Panel • Inside the building is the electric panel • Circuit breakers distribute

Good Workmanship Counts Main Breaker Neutral Cable ties Ground Smooth bends in the wires Typical 1Ø Electric Panel Circuit Breakers Bus Bars © 2005 Refrigeration Training Services - E 4#1 Power Distribution, Delta & Wye Systems v 1. 2 12