National Electrical Safety Code

1
National Electrical Safety Code
Whats New In 2002 Edition
Significant Changes to Section 23 - Clearances
Jerry Reding NESC Subcommittee 4 July 2001
2
Summary

• Introduce Each Rule Category in Section 23
• Describe Any Significant 2002 Changes
• Brief Reason for Each Change

3
Basis For Computing Clearances
4
Rule 230 - General

• No Significant Changes in 2002

5
Rule 231 - Structures and Other Objects

• Clearances of Supporting Structures From Other
  Objects

6
Rule 231A - Fire Hydrants

• Not less than 1.2 m (4 ft) ...
• Revised Rule
• Clearance changed to recommendation
• Exception aligned with previous clearance

7
Rule 231B1 - From Streets, Roads,...

• Where there are curbs
• Revised Rule
• Included anchor guys
• Defined redirectional curbs
• Defined paved or swale-type curbs and placed
  facilities behind such curbs

8
Rule 232 - Vertical Clearances

• Vertical Clearances of Wires, Conductors, Cables,
  and Equipment Above Ground, Roadway, Rail, or
  Water Surfaces

9
Rule 232B3 - Equipment Cases

• Clearance to Support Arms and Equipment Cases
• Revised to include Support Arms

10
Rule 232B4a - Street Area Lighting

• a. The vertical clearance of street and area
  lighting
• Revised
• Include vertical clearances of street light
  luminaries above ground.

11
Table 232-1, Footnote 13

• Where this construction crosses over or runs
  along alleys, not subject to truck traffic
• Revised
• Clarify for use in areas not subject to truck
  traffic.

12
Table 232-1, Footnote 26

• When designing a line to accommodate oversized
  vehicles, clearance values shall be increased by
  the difference between the known height of the
  oversized vehicle and 4.3 m (14 ft).
• New
• Clarify treatment of large vehicles.

13
Table 232-2 - Category 2a

• Add footnote 7 lessor clearances for grounded
  equipment cases to Category 2a Roads, Streets,
  and alleys
• Revised
• Allow reduced clearances for equipment if it does
  not overhang roadway.

14
Rule 233 - Different Structures

• Clearances Between Wires, Conductors, and Cables
  Carried on Different Supporting Structures

15
Rule 234 - Other Installations

• Clearances of Wires, Conductors, Cables, and
  Equipment From Buildings, Bridges, Rail Cars,
  Swimming Pools, and Other Installations

16
Rule 234C3a - Attached to Buildings

• Energized service drop conductors
• 1) For 0 to 750 V, Rules 230C or 230 D
• 2) For over 750V, Rule 230C1
• Revised
• Include service voltages over 750 volts.

17
Rule 234C3c - Attached to Buildings

• Wires or cables attached to and run along side
  the installation not less than 75 mm (3 in).
• Revised
• Calls out a specific value instead of referencing
  a table.

18
234C3d(1) - Attached to Buildings

• EXCEPTION 1 Where the voltage between
  conductors cable meets Rule 230C1
• Revised
• Include voltages and cables over 750 volts.

19
Rule 234F - Grain Bins

• All portions of grain bins In addition, the
  following clearances shall also apply
• a. A clearance not less than 5.5 m (18 ft)
• b. horizontal clearance not less than 4.6
  m (15 ft)

20
Rule 234F - Grain Bins (cont)

• Revised
• Clearances based on physical distances instead of
  voltage class.

21
Rule 235 - Same Supporting Structure

• Clearance for Wires, Conductors, or Cables
  Carried on the Same Supporting Structure

22
235C2b(1) - Between Line Conductors

• c) For purposes of this determination
• Adds new rule c) which has summer loading (i),
  winter loading (ii), and an exception for a
  single utility with equal cables.
• Revised
• Re-organized the rule for clarity under various
  loading conditions. Excludes cables of same type
  and single ownership.

23
Rule 235H - Communication Spacing

• Clearance and Spacing Between Communication
  Conductors, Cables, and Equipment
• New
• Adds guidance for placing communication equipment
  on structures.

24
Rule 235I - Communication Antennas

• Clearances in Any Direction From Supply Line
  Conductors to Communication Antennas in the
  Supply Space Attached to the Same Supporting
  Structure
• New
• Handle communication antennas located in the
  supply space, which is becoming a common practice.

25
Rule 236 - Climbing Space

• Climbing Space
• No Significant Changes in 2002

26
Rule 237 - Working Space

• Working Space
• No Significant Changes in 2002

27
Rule 238 - Communication Supply

• Vertical Clearances Between Certain Communication
  and Supply Facilities Located on the Same
  Structure
• No Significant Changes in 2002

28
Rule 239 - Other Facilities On Structure

• Clearances of Vertical and Lateral Facilities
  From Other Facilities and Surfaces on the Same
  Supporting Structure

29
Rule 239A6 - Guards Protection

• 6. Where guarding and protection are required by
  other Rules,
• New
• Clarifies such guards should completely enclose
  the cable to ensure their protection.

30
Table 239-1 - Footnote 5

• 5These clearances may be reduced to not more than
  25
• New
• Footnote added to Row 2 of Table. Provide same
  reduced clearances as conductors from guy
  insulators.