1. E4 Electrical Installation
#1 Power Distribution, Delta
and Wye Systems

2. Electrical Distribution
200,000 – 400,000 Volts
208/480 Volts
Three Phase (3Ø)
7200 Volts
Transformer
Drops Voltage
Transformer
Drops Voltage
7200 Volts
Substation
Transformers
Drop Voltage
To 7200 Volts
120/240 Volts
Single Phase (1Ø)
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

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.
Sometimes the building is far from the pole. The high voltage is run underground to a transformer nearer the building.
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

4. 1 Pole, 2 Houses, 2 Transformer Types
Line Voltage 7200 Volts
Tap for 7200v
7200v Primary
Ground
Fuse
240/120v Secondary out of transformer
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 v1.0

5. Transformers
Following is a picture of an underground service transformer
The transformer is stepping down 7200 volts to 240/120 volts.
Note the safety precautions by the power company technician
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

6. Underground Service Transformer
Eye Protection
Rubber Arm Shields
Thick Rubber Gloves
Transformer 7200v
Primary
120/240v
Secondary
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

7. Electric Meter Meter hub on a residence
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

8. Power out to electric panel
Meter Enclosure
Power In
Electric Meter
Power out to electric panel
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

9. Residential Single Phase Power
Following is a diagram of 120/240 volt 1 Ø power
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

10. Common Residential 120/240v-1Ø
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

11. Electrical Panel Inside the building is the electric panel
Circuit breakers distribute the power
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

12. Good Workmanship Counts
Main Breaker
Neutral
Cable ties
Ground
Typical 1Ø Electric Panel
Smooth bends in the wires
Nice
Job!
Circuit Breakers
Bus Bars
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

13. Commercial Power – WYE Wiring
Most commercial applications use the “Wye” power configuration
The diagram looks like a “Y”
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

14. Wye Hookups 120/208v-3Ø L1 L3 Wye 4-wire Schematic Diagram
Wye Configuration L1 L2 L3 N N
208v
208v
120v L2
208v
120v
120v
120v
120v
120v
208v
208v
208v
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

15. Delta Wiring Another commercial configuration is the “Delta”
Its name is derived from the Greek symbol “∆” for Delta.
Delta wiring has a “high leg” when one particular power leg is used with a neutral
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

16. 4-wire Schematic Diagram
Delta Hookups 120/240v-3Ø
Delta Configuration
4-wire Schematic Diagram L1 L1 L2 L3 N N L3 L2
120v
120v
208v
240v
240v
120v
240v
240v
240v
120v
240v
208v
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

17. END OF Power Distribution, Delta & Wye Systems
© 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0