2. 4
Wiring Systems

3. Objectives
Know where to find codes and authorities for an installation.
Recognize the marks of the most popular testing agencies.
List the different conductor systems used in residential and light commercial wiring.
Explain the basics of conduit bending.
Become familiar with the many different types of raceway systems.

4. National Electrical Code (NEC)
Rules, regulations, and criteria for installation of electrical equipment
Revised every three years
Compliance typically mandated by state or local building codes
“Authority having jurisdiction”—person responsible for approving electrical installations

5. Code Alert Article 90 defines what is and is not covered by the NEC
Article 100 provides definitions of essential terms used throughout the NEC
Article 110 provides general requirements for electrical installations

6. State and Local Codes
All electrical construction governed by state or local building codes
Be aware of specific codes based on location and type of construction
Codes generally require
Licensing
Permits
Inspection/approval

7. Additional Organizations
Nationally recognized testing laboratories
Test materials and equipment
Underwriters Laboratories
Occupational Safety and Health Administration (OSHA)
Agency of US federal government
Required safe practices

8. Wiring Systems
Wiring system—Wiring and related components used in an electrical system
Two primary classifications:
Cables
Raceways

9. Armored Cable (AC) Also called “BX” Components: Armor (outer covering)
Insulated conductors
Bonding strip (for equipment grounding system)

10. Armored Cable (AC) (cont.)
Requires anti-short bushings to protect conductors from sharp edges of armor

11. Armored Cable Connectors

12. Nonmetallic Sheathed Cable (NM)
Also called “Romex”

13. Stripping Nonmetallic Sheathed Cable

14. Service Entrance Cable (SE)
Overhead cable
Connects utility company transformer to home’s service panel
Underground service entrance cable (USE)
Below-grade service connections
Underground feeder and branch-circuit cable (UF)
Similar to NM but designed for below-grade use

15. Code Alert Typical requirements for cable support
Cable must be supported within 12 of a box
Maximum distance between cable supports is 4-6
Always check support requirements for specific cable type being used

16. Raceways Protective tubing installed to house conductors
Conduit—tubing connecting boxes and devices in a wiring system

17. Common Raceway Systems
Electrical metallic tubing (EMT)
Electrical nonmetallic tubing (ENT)
Rigid metal conduit (RMC)
Rigid PVC conduit (PVC)
Intermediate metal conduit (IMC)
Flexible metal conduit (FMC)
Liquidtight flexible metal conduit (LFMC)
Surface-mount raceways

18. Electrical Metallic Tubing (EMT)
Also called “thin-wall” conduit
Not threaded
Tubing serves as equipment grounding conductor—proper connections are critical

19. EMT Connections

20. Cutting Metal Conduit Cutting tools:
Hacksaw
Reciprocating saw
Pipe cutter
After cutting, use reamer, file, or deburring tool to eliminate sharp edges

21. Bending Metal Conduit
Field bend—Conduit bend made on the construction site
Generally, bending is easier and less costly than using fitting
Always use the correct size conduit bender
Always know the minimum bend radius allowed by code

22. Stub Bend

23. Back-to-Back Bend

24. Offset Bend

25. Offset Bend (cont.) Preparation Measure distance to obstruction
Measure height of obstruction
Use offset bend chart to determine
Angle of offset
Distance between bends
Shrink

26. Offset Bend (cont.) Marking conduit
Add shrink to the distance to the obstruction, and mark conduit at this distance
Measure back the distance between bends

27. Offset Bend (cont.)

28. Box Offset

29. Saddle Bend Two 22 1/2 bends and one 45 bend Preparation
Measure height of obstruction
Find distance from start of conduit to center of obstruction, then add 3/16 for every inch of obstruction height (for 1/2 conduit). Mark this location (center of bend)
On each side of center mark, measure and mark a distance equal to 2 1/2 times the height of the obstruction

30. Saddle Bend (cont.)

31. Electrical Nonmetallic Tubing (ENT)
Often called “smurf tube” or “smurf”
Corrugated, flexible plastic
Easy to install
Cannot be buried or left exposed

32. Rigid Metal Conduit (RMC)
Galvanized pipe, similar to water pipe
Threaded connectors and fittings
Conduit part of equipment grounding system
RMC has thicker walls than EMT has

33. RMC Connectors and Fittings

34. Rigid PVC Conduit (PVC)
Hard plastic conduit
Lighter than metal conduit
Can be heated and bent
Conduit joined to fittings with glue

35. PVC Connections

36. Other Raceway Systems Intermediate metal conduit (IMC)
Walls thicker than EMT and thinner than RMC
Flexible metal conduit (FMC)
Also called “Greenfield”
Similar to armored cable casing
Liquidtight Flexible Metal Conduit (LFMC)
Similar to FMC with a plastic sheath
Surface-mount raceways