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Motor Installation By Bill Lee

Motor Installation By Bill Lee. Article 430. All Motors 460V. D.E.T.D. Fuse. Feeder O.C. O.L. N.T.D. NF. Brach Circuit. 15HP. FLA 20A 40 Temp Rise. Feeder Conductors. IV. Time. NF. FLA 30A S.F. 1.15. 25HP. D.E.T.D. NF. 30HP. FLA 38A. N.T.D. NF. 50HP. FLA 63A

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Motor Installation By Bill Lee

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  1. Motor InstallationBy Bill Lee Article 430

  2. All Motors 460V D.E.T.D. Fuse Feeder O.C. O.L N.T.D NF Brach Circuit 15HP FLA 20A 40 Temp Rise Feeder Conductors IV. Time NF FLA 30A S.F. 1.15 25HP D.E.T.D NF 30HP FLA 38A N.T.D NF 50HP FLA 63A 40 Temp Rise IV. Time NF 75HP FLA 93A S.F. 1.10

  3. Motor Calculations • Article 430.62 requires that Feeder Overcurrent device be sized based on the largest overcurrent in the group (based of Feeder % multiplier). This is to be added to the Full-Load Currents of all other motor supplied by that feeder. • This code section does not allow for the next available overcurrent device as permitted for individual overcurrent devices. • Calculation as follows…

  4. Feeder Calculations continued… • Largest motor has FLC of 96A… • 96A x 175% (Feeder Type) = 168A • 168A is not a standard size code permits • 175A overcurrent device. • 175A + 21A + 34A + 40A + 65A = 335A • Feeder must be sized to next lower O.C. • Answer 300A

  5. Feeder Conductor Calculation… • Article 430.24 requires that all feeder conductors be sized at “not less than” the sum total of all motor FLC plus the largest motor FLC at 125%... • (Largest Motor) 96A x 125% = 120A • 120A + 21A + 34A + 40A + 65A = 280A • Table 310.16 requires… 300kcmil cu.

  6. Individual Brach Circuit Overcurrent • Per Article 430.52 overcurrent is sized… • (15HP) 21A x 300% = 63A… 70A • (25HP) 34A x 250% = 85A… 90A • (30HP) 40A x 175% = 70A… 70A • (50HP) 65A x 300% = 195A… 200A • (75HP) 96A x 250% = 240A… 250A

  7. Brach Circuit Conductors • Article 430.22 requires that all conductors be sized at “not less than” 125% of the FLC of the Motor. • Article 110.14 (c) (4) allows motors (types B, C and D) to use the 75 degree C ampacities of table 310.16 • Calculations will be as follows…

  8. Branch Circuit Conductors continued… • 21A x 125% = 26.25A… #10 cu • 34A x 125% = 42.5A… #8 cu • 40A x 125% = 50A… #8 cu • 65A x 125% = 81.25A… #4 cu • 96A x 125% = 120A… #1 cu

  9. Branch Circuit Disconnects • Article 430.110 (A) requires that disconnects be sized at no less that 115% of the FLC of the Motor supplied… • 21A x 115% = 24.15A… 30A • 34A x 115% = 39.1A… 60A • 40A x 115% = 46A… 60A • 65A x 115% = 74.75A… 100A • 96A x 115% =110.4A… 200A

  10. Overload Protection • Article 430.32 requires overload protection to be sized based on the FLA of the motor protected… • 20A x 125% = 25A… 25A • 30A x 125% = 37.5A… 37.5A • 38A x 115% = 43.7A… 43.7A • 63A x 125% = 78.75A… 78.75A • 93A x 115% = 106.95A 106.95A

  11. All Motors 460V 300A 30A 70A 25A #10 Cu 15HP 60A 67.5A 90A # 8cu 25HP 60A 43.7A 70A #8 cu 30HP 100A 200A 78.75A #4 cu 50HP 200A 250A 106.95A #1 cu 75HP 300kcmil cu

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