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Determine Conduit size - Electrical conduit size Determine conduit size: conduit size The rigid metal conduit sizing is determined by using table C.8 NEC 2008 on page 70-739. Do these steps 1. ( Find cable size) 2. Apply following table Conductor size (AWG/ Kcmil) MD (TD) 16 (1/2) MD (TD) 21 (3/4) MD (TD) 27 (1) MD (TD) 35 (11/4) MD (TD) 41 (11/2) MD (TD) 53 (2) MD (TD) 63 (21/2) MD (TD) 78 (3) MD (TD) 91 (31/2) MD (TD) 103 (4) MD (TD) 129 (5) MD (TD) 155 (6) 14 12 10 8 6 4 3 3 1 1 7 6 5 2 1 12 10 8 4 3 21 17 14 7 6 28 23 19 10 8 46 38 31 16 13 66 55 44 23 18 102 85 68 36 29 136 113 91 48 38 176 146 118 61 49 276 229 185 87 77 398 330 267 139 112 4 3 2 1 1 1 1 0 1 1 1 1 2 2 1 1 4 4 3 1 6 5 4 3 10 9 7 5 14 12 11 7 22 19 17 11 30 26 23 15 38 34 29 19 60 53 46 30 87 76 66 44 1/0 2/0 3/0 4/0 0 0 0 0 1 1 0 0 1 1 1 1 1 1 1 1 2 2 1 1 4 4 3 3 6 5 4 4 10 8 7 6 13 11 10 8 17 14 12 11 26 23 20 17 38 33 28 24 250 300 350 400 500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 2 2 1 1 4 4 4 3 3 6 5 5 4 4 8 7 6 6 5 13 11 10 9 8 18 16 15 13 11 NOTE This table is just a portion of table C.8 Apply only for RHH,RHW,RHW-2 MD stands for Metric Designator TS stands for Trade Size Metric Designator Trade Size 12 16 21 27 35 41 53 63 78 91 103 129 155 3/8 1/2 3/4 1 1 _ 1/4 1_ 1/2 2 2_ 1/2 3 3_ 1/2 4 5 6 The metric designators and Trade sizes are for identification purposes only and are not actual dimensions Apply the table C.8: If cable type is RHH, or RHW, or RHW-2 Cable size is 14 AWG, then: Maximum 4 cables can be combined in a ½ inch rigid metal conduit size.
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