Exam (elaborations)
26401 Load And Feeder Calculations: Q’s And A’s (A+)
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26401 Load And Feeder Calculations: Q’s And A’s (A+)
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26401 Load And Feeder Calculations: Q’s And A’s (A+)What is the minimum demand required for the portion of a feeder that
supplies 30ft of show window? Right Ans - NEC 220.43 (A) Show windows
30ft x 200va = 6000 va
Residential Small apliance circuits must be rated at __________ per NEC
220.52(A) Right Ans - 1500 va
When performing load calculations for farm buildings the load that must be
included in the calculation at 100% demand must be at least _______ . Right
Ans - 60 amps
The demand lighting load for a 20,000 square foot motel with no dining room
or ballroom is ____ per NEC 220.12 and 220.42 Right Ans - 220. 14(M) 1.7
volt amperes per square foot. 18,000 va
What is the demand lighting load for a 100,000 square foot hotel with no
dining room or ballroom is ____ per 220.12 and 220.42 ? Right Ans - 72,000
va
When calculating the feeder load for a motor Control Center supplying several
Motors per 430.24 you must ______ . Right Ans - Determine the sum of all
the motor loads plus 25% of the largest motor.
A commercial kitchen with six or more pieces of kitchen equipment is subject
to a demand factor of ___________ per NEC table 220.56. Right Ans - 65%
demand factor
What is a tap conductor? Right Ans - When the overcurrent protection for a
conductor is located on the load side rather than the supply side of a
conductor, it is considered to be a tap conductor
What is the minimum general lighting load in volt-amps per square foot
required by the NEC table 220.12 for a store? Right Ans - 3va per s.f.
What is the total load center length for a tapped feeder with loads of 120a at
50 feet, 110a at 60 feet, 75a and 90 feet, and 70 amps at 150 feet? Right
Ans - •120a x 50ft = 6000
, •110a x 60ft = 6600
•75a x 90ft = 6750
•70a x 150ft = 10,500
•6000+6600+6750+10,500 = 29,850
•120a+110a+75a+70a = 375a
•29,a = 79.6 ft load center length
The minimum ampacity for a feeder supplying ten 30a shore power
receptacles in a marina is _____ per NEC table 555.12 Right Ans - •Table
555.12
•9-14 receptacles @ 80%
•10 receptacles x 30a = 300a
•Apply the demand factor from 555.12 300a x 80% = 240a
The minimum ampacity for a feeder supplying (30) shore power receptacles
in a marina each rated at 30a is _____ per NEC table 555.12. Right Ans -
•Table 555.12
•15-30 receptacles @ 70%
•30 receptacles x 30a = 900a
•Apply the demand factor from 555.12 900a x 70% = 630a
•What is the total load for a feeder serving
•(4) 2 horsepower motors 7.5a
•(3) 5 horsepower Motors16.7a
•(1) 15 horsepower 46.2a motor
•(1) 25 horsepower motor ? 74.8a
•(all Motors are 208 volts) Right Ans - •Use Table 430.250
•7.5 amps x 4 = 30a
•16.7amps x 3 = 50.1a
• 46.2 amps x 1= 46.2a
• 74.8 amps x 100% = 74.8
•74.8a x .25% = 18.7a (add additional 25% for largest motor load)
•30+50.1+46.2+74.8+18.7=219.8a or 30+50.1+46.2+93.5 = 219.8a
What is the feeder ampacity for a three phase, 120/208 Volt subpanel with a
connected load of 84,563 Volt amps? Right Ans - •84,563 va / 208volts =
406.5522
•Don't forget it's three phase! = 1.732
•406..732 = 234.89a
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