1. Objectives Review conductor and conduit selection
Learn about protection systems (basic rules)
Learn to design Residential Electrical Systems

2. Current-Carrying Capacity
Ref: Tao and Janis (2001)

3. Tubing size
Ref: Tao and Janis (2001)

4. Other Issues
In general, no more than 40% of raceway can be filled with wiring
Why?
To prevent extensive heat up
To prevent physical installation of wires

5. Conductor Rules Explain each of the following: In the same conduit:
No more than 4 90 ° bends are allowed between pull boxes
In the same conduit:
No mixing of high- and low-voltage conductors
No mixing control and power conductors
No mixing phone and power conductors
Do place all three phases in the same conduit

6. Receptacles and switches
Receptacles (duplexes)
Number
Shape
Voltage rating
Current Rating
Number of poles and wires
Switches
Type (NEC rating)
Contact method
Speed of operation
Voltage rating
Number of poles
Method of operation
Enclosure
Duty
Other (dimming)

7. Protective Devices What are we protecting from? Circuit breakers
Overcurrent
Overvoltage
Circuit breakers
Switch that responds to thermal or short circuit loads
Can be bimetal, magnetic, or electronic
Reusable, remote control, compact, can be used as
disconnect switch
Fuses
Melting metal
Self destructive, larger

8. Why use fuses instead of circuit breakers?
Fuses can be used multiple times
Fuses are more aesthetically pleasing
Fuses are safer
Fuses cause less damage to equipment

9. Ref: Tao and Janis (2001)

10. Emergency power systems Batteries Power generators
Motor starters
ON-OFF switches are NOT for motors
Motor circuit-rated switches
Reduce the current during the start
until the motor rich full speed
Protect the motor form overload
Emergency power systems Batteries Power generators

11. Residential Systems Very little variation between different houses
Many similarities to commercial buildings
Particularly as you get close to end uses
Need to be watchful for unusual circumstances

12. Procedure Analyze building needs Determine electrical loads
Select electrical systems
Coordinate with other design decisions
Prepare plans and specifications

13. List of needs Appliances (incl. HVAC) Receptacles Lighting
Ground fault protected (GFI/GFCI)
Switched
Lighting
Switches
Ceiling Fans

14. Example House Master Bedroom Bathrooms
Entry and Outdoor (AC compressor)
Bedrooms
Dining and Mechanical Closet (resistance heat)
Kitchen (appliance circuits, range, oven)
Family
Garage/Laundry/Closet (resistance water heater, dryer)

15. Outdoor
Bathroom
Closet
Bedroom 2
Laundry
Kitchen
Bathroom
Mechanical
closet
Family room
Master
Bedroom
Entry
Bedroom 3
Dining
Garage

16. NEC about receptacles
No longer approve non-polarized and ungrounded receptacles in new installations.
Each receptacle (duplex) is rated for 1.5 A.
For 120 V: Each duplex 1.5×120 = 180W

17. Residential system sizing
Typically 3 wire 1 phase system 120/240 V
Procedure defined by NEC article 220:
Identify characteristic electrical loads
Add lighting (3W/ft2)
Add two 20 Amps circuits for kitchen
Add one 20 Amps circuit for laundry
Electricity for HVAC equipment based on requirement for heating or cooling

19. Summary of Power Sizing
Include enough capacity for heating and cooling
Work through kitchen and then other rooms
Include any items that are unusual
Take first 10 kVA and then 40% of remaining load

20. Panel Sizing Find panel power usage and neutral usage
Size panel conductors and associated conduit and switches

21. Electric panel - 3 wire 1 phase 120/240

22. Homework 5 - problem 2 Sizing the residential electrical system
Defined by NEC article
Similar to the example we worked out
You need to collect the data for several characteristic consumers
Includes conductor sizing