Box and Conduit Fill Calculations

Transcription

1 Box and Conduit Fill Calculations

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3 Volume required per conductor

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6 Conduit fill - Box sizing Table (a) : Number of conductors in box 600v, nominal or less CONDUCTORS: 1. Conductors originating outside box, terminating in box count as 1 conductor 2. Conductors originating outside box, spliced in box counts as 1 conductor 3. A conductor entering a box, spliced to a conductor leaving box counts as 2 conductors 4. Conductors passing through box without splices or terminations count as 1 conductor 5. A conductor of which no part leaves the box shall not be counted

7 Conduit fill - Box sizing 2005 NEC Change Looped conductors now count as 2 conductors

8 EQUIPMENT GROUNDING CONDUCTOR: 1. One, two or more bare, insulated or covered system grounding conductors all count the same size, count as 1 conductor 2. One, two or more bare, insulated or covered system grounding conductors of various sizes, count as one conductor based upon largest equipment grounding conductor 3. A separate ISOLATED equipment grounding conductor counts as 1 conductor in addition to system grounding conductor. Count as size of ISOLATED grounding conductor or largest if various sizes.

9 CLAMPS: 1. Clamps installed inside box by factory count as 1 conductor 2. Clamps installed in box in the field count as 1 conductor (Conductor size based on largest conductor in box) SUPPORT FITTINGS: 1. Fixture studs count as 1 conductor 2. Fixture hickeys count as 1 conductor (Conductor size based on largest conductor in box)

10 DEVICE(S) IN BOX: 1. Yoke or strap with switch, counts as 2 conductors 2. Yoke or strap with duplex receptacle counts as 2 conductors 3. Yoke or strap with triplex receptacle counts as 2 conductors 4. Yoke or strap with switch & light on same yoke or strap counts as 2 conductors 5. Yoke with any combination of three devices on same yoke or strap counts as 2 conductors (Conductor size based on LARGEST conductor connected to device or equipment)

11 Yoke or Strap

12 Conductor Counts for other than wire Cable Clamps NM 12-2 W/GRD Hickey Fixture Stud Fixture Stud = 1 Conductor Hickey = 1 Conductor Cable Clamps (2) = 1 Conductor Total Conductor Count = 3 Conductors

13 1 Yoke 1 Device 1 Conductor Counting Devices 1 Yoke 3 Devices 1 Conductor 1 Yoke 1 Device 1 Conductor 1 Yoke 2 Devices 1 Conductor

14 Through Box Terminate in Box Through Box 2 Terminate in Box 4 Total Count = 6 All Conductors Terminate in Box Count 6 total conductors

15 Factory installed clamps 8-12 s s & 1 clamp = 9 Box & conduit Fill Calculations Factory or Field Installed Clamps #12 AWG #12 AWG

16 EGC = Equipment Grounding Conductor IEGC = Insolated Equipment Grounding Conductor BJ = Bonding Jumper Box & conduit Fill Calculations BJ EGC = 1 IEGC = 2 BJ = 0 Total = 2 EGC IEGC To Receptacle

17 Octagonal / 4/0 Box 2 - #8 AWG 2 - #12 AWG 2 - #12 AWG 2 - Cu = 6 Cu in Fix Cu in = 3 Cu in 4 - Cu in = 9 Cu in Total = 18 Cu in

18 #14 Bare EGC #8 AWG #12 AWG #18 AWG fixture wire #10 AWG #18 = 1.5 cu in x 2 = 3.00 cu in #14 = 2.0 cu in x 1 = 2.00 cu in #12 = 2.25 cu in x 4 = 9.00 cu in #10 = 2.50 cu in x 2 = 5.00 cu in #8 = 3.00 cu in x 2 = 6.00 cu in Fix Stud = #8 = 3.00 cu in = 3.00 cu in Total Box volume required = 28,00 cu in

19 Bad Planning

20 314.16(b)(1) Exception Canopy Cover Box & conduit Fill Calculations 4 - Smaller than #14 Fixture wires EGC Terminations in Canopy Cover Dome Canopy To Fan To Fixture Do not count for Box Fill Calculations

21 Counting with a device Box & conduit Fill Calculations 2 - #8 AWG 2 - #12 AWG Largest conductor allowed = #10 NEC (A) 2 - #12 AWG 2 - cu in = 6 cu in 4 - cu in = 9 cu in cu in = 4.5 cu in Total Volume Required = 19.5 cu in

22 Conduit Fill Calculations

23 Major Fraction Change Box & conduit Fill Calculations

24 What size EMT is needed for 3-2/0 AWG THW Cu conductors and 4-4/0 AWG THHN Cu conductors?

25 What size EMT is needed for 3-2/0 AWG THW Cu conductors and 4-4/0 AWG THHN Cu conductors? Table 5 Cross-Sectional Area of Individual Conductors 2/0 AWG THW Cu =.2624 X 3 = /0 AWG THHN Cu =.3237 X 4 = Total Square Inches for Conductors = Table 4 40% fill column for Over 2 wires Sq.In. Requires a 2 ½ inch EMT Conduit 40% fill for 2 ½ inch EMT = Sq. In. Answer = 2 ½ Inch EMT

26 What size IMC is required for 6-12 AWG RHH Cu conductors without outer covering and 4-14 AWG RHH Cu Conductors with outer covering?

27 What size IMC is required for 6-12 AWG RHH Cu conductors without outer covering and 4-14 AWG RHH Cu Conductors with outer covering? Table 5 Cross-Sectional Area of Individual Conductors 14 AWG RHH Cu With Outer Covering =.0293 X 4 = AWG RHH Cu Without Outer Covering =.0260 X 6 =.1560 Total Square Inches for Conductors =.2732 Table 4 40% fill column for Over 2 wires Sq.In. Requires a 1 inch IMC Conduit 40% fill for 1 inch IMC =.384 Sq. In. Answer = 1 Inch IMC

28 Box & Conduit Fill Exam 10 Questions 30 Minutes

29 Box fill Answers Box & conduit Fill Calculations 1. (b) cu in (b) 3 - # cu in = 6.75 cu in 2. (b) 2 conductors (b) 3. (b) 4 Table (a) 2 - # cu in = 4.00 cu in 4. (d) 17.5 cu in Table (b) #10 = 2.5 cu in 7 - #10 s x 2.5 cu in = 17.5 cu in cu in 5. (a) in 2 Table 5 (note * notations by insulations) * ONLY APPLIES TO RHH,RHW,RHW-2

30 Box fill Answers Box & conduit Fill Calculations 6. (d) cu in Table (b) #8 = 3.00 cu in #12 = 2.25 cu in Clamps - #8 = 3.00 cu in cu in = cu in cu in = 3.00 cu in cu in = cu in cu in

31 3 - #8 ungrounded conductors count as 3 {314.16(b)(1)} 3 - #8 grounded conductors count as 3 {314.16(b)(1)} 3 - #8 grounding conductors count as 1 {314.16(b)(5)} 4 - clamps count as 1 {314.16(b)(2)} 3 - #12 ungrounded conductors count as 3 {314.16(b)(1)} 3 - #12 grounded conductors count as 3 {314.16(b)(1)} 3 - #12 grounding conductors count as 1 {314.16(b)(5)} #8 conductors cu in = cu in Clamps cu in = 3.00 cu in #12 conductors cu in = cu in cu in

32 7. (b) in² T.5 8. (b) 1 1/4 IMC T.4 9. (a).384in² T (C).2637in² T.5