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TTS 171 : PART 1: 2002

TTS 171 : PART 1: 2002. ANNEX E PRESENTER WINSTON THOMAS. ELECTRICAL INSPECTOR 1. MAXIMUM CONDUCTORS IN CONDUIT AND BOXES. Objective Simple guide Calculation. Cont’d. Maximum number of cables Conduits Boxes. CONDUITS. Electrical Metallic Tubing or E.M.T

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TTS 171 : PART 1: 2002

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  1. TTS 171 : PART 1: 2002 ANNEX E PRESENTER WINSTON THOMAS ELECTRICALINSPECTOR 1

  2. MAXIMUM CONDUCTORS IN CONDUIT AND BOXES • Objective • Simple guide • Calculation

  3. Cont’d. • Maximum number of cables • Conduits • Boxes

  4. CONDUITS • Electrical Metallic Tubing or E.M.T • Steel heavy gauge conduit • PVC conduit

  5. Surroundings Ambient temperature Level of mechanical protection APPLICATION

  6. CAPACITIES • For the maximum capacities • Reference to Annex E • Relevant table

  7. TABLES IN ANNEX E Four tables Maximum PVC insulated non sheathed cables Space factor of 40 %

  8. Cont’d. • Two 900 bends • Additional bends • Cables reduced

  9. USE OF TABLES • Calculate number of cables for circuit • Choose cable size in column • Use maximum number of cables column

  10. Cont’d. • Choose value equal to or greater than number of cables • Go to corresponding column for conduit size

  11. TABLE E 2a • Covers maximum capacities • Steel conduit and E.M.T • PVC insulated non-sheathed single core cables

  12. Cont’d. • Same cross-sectional area • Imperial, AWG or MCM and Metric sizes

  13. Example A 115/230V single phase a.c circuit requiring 16mm2 single core cables is to be run in an E.M.T conduit . To determine conduit size.

  14. Calculate Number of cables. (3) Cable size column. (16mm2) Maximum number cables column. (4) Corresponding conduit size of 27 mm or (1 in).

  15. Table E 2b • Covers maximum capacities. • Steel heavy gauge conduits. • PVC insulated cables of same cross-sectional area.

  16. Example Using three 16mm2 cables as in the previous example. Follow same steps. Conduit size approximately the same.(25mm)

  17. Table E 2c • Covers maximum capacities. • PVC conduits • PVC insulated cables of same cross-sectional area

  18. Example Same circuit to be run in PVC conduit. A grounding conductor is now required. Number of cables. ( 4 )

  19. Cont’d Maximum number of cables column. (5) Conduit size - 32mm

  20. Table E1 • New addition to code. • Covers maximum capacities. • All types of conduits.

  21. Cont’d • PVC insulated cables of different cross-sectional areas • Conduit factor • Conductor factor .

  22. Four 2.5mm 2 , four 4.0mm 2 and two 6.0mm 2 cables, are to be drawn into a conduit. Total conductor factor = Sum of cable conductor factors. Example

  23. Cont’d. Conduit factor shall be equal to or greater than total conductor factor.

  24. 4 x 4.0mm2 factor = 4 x 39 = 156 2 x 6.0mm2 factor = 2 x 50 = 100 Total 376 Conduit factor - 486 Conduit 27mm ( 1 in. ) 4 x 2.5mm 2 factor = 4 x 30 = 120

  25. CAPACITIES OF BOXES Table E 3 • New addition to code. • Maximum capacities. • Outlet and junction boxes

  26. Sixteen 4.0mm2 cables to be spliced in a box. Determine size of box. First go to column for 4.0mm cables. Example

  27. Cont’d. Then to row where value is equal to or greater than sixteen. Then to box in corresponding row. (4 11/16 x 2 1/8)

  28. THE END

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