Basic Electrical Design NEC Code Applications Class 101

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Basic Electrical DesignNEC Code
ApplicationsClass 101

• Jim Fuller
• 4/9/08

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Objective

• Electrical Working Clearances
• Working space for 600V or less
• Working space of greater than 600
• Pull box sizing
• Using Conductors Smaller than 4 AWG and all the
  Same Size
• Using Conductors Smaller than 4 AWG and different
  Sizes
• Straight Pull - Using Conductors Larger than 4
  AWG
• Angle Pull - Using Conductors Larger than 4 AWG

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Egress for Switchboard over 1200AEgress incase
of fire use two doors or double the
workspaceNEC 110.26
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Working Space less than 600VNEC 110.26
480V Equip. working space rule 3ft, 3 1/2ft or
4ft
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Working Space less than 600VNEC 110.26
Working space three directions 30 wide, 36
in front, 6.5 ft height
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Working Space less than 600VNEC 110.26
Space for electrical conduits tray. No
non-electrical equipment unless above 6ft
Working space three directions 30 wide, 36
in front, 6.5 ft height
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30 inch rule Working space for panels NEC 110.26
6 ½ feet headroom rule
30 inch rule
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High Voltage ClearanceNEC 110.30 to 34
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Pull Box Sizingcable larger than 4 awg

• Straight Pull 8 x largest conduit
• Angle Pull6x largest conduit plus the size of
  other conduits

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Sample Problem Straight PullNEC 314.28.A.1

• NEC Article 314.28.A.1..
• 8 time the largest conduit

Length of pull box 8 x 3 conduit 24 inches
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Sample Problem Straight PullNEC 314.28.A.1

• Problem
• What size box for (1) 3 inch conduit and (2) 2
  inch conduit for straight pull. Assume cable are
  greater than 4 AWG.
• Length 3 C x 8 24
• Width clearance between 3C 2C clearance
  between 3C 2C ends
• Width 4.254.7543 16
• Depth distance for locknut for 3 4 3/16
• Choose 24x16x6

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2
3
4.75
4
3
4..25
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Sizing pull box for right angle pull NEC
314.28.A.2

• NEC Article 314.28.A.2..
• a sum of all conduit diameter plus 6 time the
  larges conduit diameter

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Sizing pull box for right angle pull NEC
314.28.A.2
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Sample Problem Angle PullNEC 314.28.A.2

• Problem
• What size box for (1) 4 inch conduit and (1) 3
  inch conduit and (1) 2 conduit for right angle
  pull. Assume cable are greater than 4 AWG.
• A 6 x 4C 24
• Length 4C x 6 3 2 29 inches
• Width clearance between 4C 3C clearance
  between 3C 2C ends
• Width 5 3/8 4
• Depth 2 x largest conduit 2 x 4 8
• Box size L x W x D 37 x 33 x 8

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2
4
5.5
1.5
4
2.5
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CONDUCTORS SMALLER THAN 4 Awg. AND ALL THE SAME
SIZE CONDUCTORS IN THE BOX based on box fill
(BOX VOLUME)NEC 314.16a

• When you are calculating the total number of
  current carrying conductors in a box smaller than
  4 awg conductors and all the same gauge and type
  insulation then, in addition to counting all
  actual current carrying conductors as one current
  carrying conductor for each conductor any color
  of conductor except, green or bare, you must add
  also as current carrying conductors as follows
  NEC Article 314.16.B

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Conclusion

• Electrical Working Clearances
• Working space for 600V or less
• Working space of greater than 600
• Pull box sizing
• Using Conductors Smaller than 4 AWG and all the
  Same Size
• Using Conductors Smaller than 4 AWG and different
  Sizes
• Straight Pull - Using Conductors Larger than 4
  AWG
• Angle Pull - Using Conductors Larger than 4 AWG

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