Electrical Engineer's Portable Handbook, Second Edition

3.10: THREE-PHASE FEEDER SIZE SCHEDULE

3.10 THREE-PHASE FEEDER SIZE SCHEDULE

Table 3.75: Table 3.75 provides 3-phase, 3-wire and 3-phase, 4-wire feeder sizes based on the rating of the overcurrent protective device.

CIRCUIT SIZE SCHEDULE NOTES:

S1. UNLESS OTHERWISE INDICATED, FEEDER SIZING SHALL MATCH THE SIZE INDICATEO ABOVE FOR THE APPLICABLE OVERCURRENT DEVICE. PROVIDE LARGER FEEDER WHERE INDICATED.

S2. SCHEDULE IS BASED ON TYPE THHN/THWN FOR CONDUCTOR SIZES SMALLER THAN #3 AWG AND TYPE XHHW FOR CONDUCTOR SIZES #3 AWG AND LARGER.

S3. PROVIDE 4 WIRE CIRCUIT UNLESS DEVICE SERVED DOES NOT HAVE PROVISIONS FOR A NEUTRAL CONNECTION.

S4. MINIMUM SIZE CONDUIT UNDERGROUNO IS 4 INCH EXCEPT 1 INCH FOR SITE BRANCH CIRCUITS FOR LIGHTING AND MISCELLANEOUS POWER AND SYSTEMS, UNLESS SPECIFICALLY INDICATEO OTHERWISE.

S5. REFER TO TRANSFORMER SCHEDULE FOR CONDUCTOR AND CONDUIT SIZE REQUIREMENTS FOR PRIMARY AND SECONDARY FEEDERS.

S6. REFER TO MOTOR CIRCUIT SCHEDULE FOR CONDUCTOR AND CONDUIT SIZE REQUIREMENTS FOR MOTOR LOADS.

S6. CONDUIT SIZES ARE BASED ON MOST RESTRICTIVE RACEWAY TYPE AND ON NORMAL PRACTICES FOR ANTICIPATED METHODS OF INSTALLATION.

CONDUCTOR SIZES ARE BASED ON 60 C TEMPERATURE RATING FOR BREAKER SIZES 100A AND SMALLER AND BASED ON 75 TEMPERATURE RATING FOR BREAKER SIZES LARGER THAN 100A. NOT MORE THAN THREE CURRENT CARRYING CONDUCTORS SHALL BE PROMDE IN RACEWAY. CABLE OR EARTH (DIRECT BURY). BASED ON AMBIENT TEMPERATURE OF 30 C. UNLESS OTHERWISE NOTED.

CONDUIT SIZES ARE MORE RESTRICTIVE THAN ALLOWED BY CODE. RACEWAY DIAMETER MAY BE DECREASED BY ONE SIZE AND MEET THE FILL LIMITATIONS OF THE MOST RESTRICTIVE RACEWAY MATERIAL

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