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What is the MINIMUM size THWN copper conductors required to supply a continuousduty, 25 hp, 208volt, 3phase motor, where the motor is on the end of a short conduit run that contains only three (3) conductors, and located where exposed to an ambient temperature of 115 deg. F?


















To determine the minimum size required of the conductors to supply this motor, first find the fullload current rating of the motor, 74.8 amperes, from Table 430.250. Next, as per Section 430.22 multiply by 125%. Then, divide by the temperature correction factor, 0.75, from Table 310.15(B)(2)(a). Finally, select the conductor size, 1 AWG THWN, from Table 310.15(B)(16).
25 hp motor FLC = 74.8 amperes x 125% = 93.5 amperes 93.5 amps .75 (temperature correction) = 124.6 amperes
*NOTE: The wire size needs to be increased because of the elevated ambient temperature. Size 1 AWG THWN conductors with an allowable ampacity of 130 amperes should be selected.
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72.

Determine the MINIMUM size THWN copper branchcircuit conductors required by the NEC® to supply one 40 hp, 480 volt, continuous duty, 3phase, inductiontype, Design C, motor.


















To determine the minimum conductor size to supply this motor, first locate the fullload current rating of the motor, 52 amperes, from Table 430.250. Next, as per Section 430.22 multiply this value by 125%. Then, select the conductor size, 6 AWG THWN, from Table 310.15(B)(16). 40 hp FLC = 52 amperes x 125% = 65 amperes
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