Under normal circumstances what is the maximum size overcurr

Under normal circumstances, what is the maximum size overcurrent protection allowed for a 14 AWG copper conductor according to 240.4(D)? a) 15 amperes b) 20 amperes c) 30 amperes d) 50 amperes

A circuit load that is expected to be on for three hours or more is called a continuous load. At what percentage of full load current do we size conductors and over-current protection for these circuits? a) 110% b) 100% c) 125% d) 150%

A 14 amp fluorescent lighting circuit contains four conductors in the raceway with 75° C terminations and an ambient temperature of 42° C. What size copper THW conductor is required for this circuit? a) #10 AWG b) #12 AWG c) #14 AWG d) #16 AWG

What size over-current protection is required for a 133 ampere, 2-wire circuit using RHH conductors at normal ambient temperature? Assume non-continuous loading. a) 150 A b) 160 A c) 175 A d) 125 A

What is the maximum allowable ampacity of a 1/0 XHHW conductor? a) 110 A b) 125 A c) 150 A d) 175 A What is the maximum overcurrent protection that can be used on a #6 THW under continuous loading? a) 60 A b) 70 A c) 80 A d) 90 A

There are 35, #8 AWG, THW current carrying conductors in a raceway. Assuming normal ambient conditions, what is the allowable ampacity of these conductors? a) 20 A b) 40 A c) 50 A d) 60 A

There are 6, #4 AWG, XHHW current carrying conductors in a raceway. The ambient temperature is 50 C. What is the maximum overcurrent protection that can be used for this circuit assuming a non-continuous load? a) 30 A b) 45 A c) 60 A d) 70 A

There are twelve #3 THW current carrying conductors in one raceway. The ambient temperature is 125° F. What is the new ampacity of these conductors under these conditions? a) 40 amperes b) 33.5 amperes c) 30 amperes d) 20 amperes

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Solution

1.over current exists when current exceeds the rating of the equipment or the ampacity of a conductor. over current devices protect equipments and conductors from over current. The rating of over current device must be considered when sizing a conductor. According to national electrical code(NEC) 240.4(D) the over current protection for 14 AWG copper conductor LIMITS TO 15 AMPERES. S O OPTION IS A

2. when a feeder supplies a continous loads or a combination of continuous and non continuous load, neither the ampere rating of the over current device nor the ampacity of the feeder conductors shall be less than the noncontinuous load plus 125 percent of continous load. So option is A

THE MAXIMUM ALLOWABLE AMPACITY OF A 1/0 XHHW CONDUCTOR ACCORDING TO NEC

FOR COPPER CONDUCTORS 150 AT 75 DEGREES AND 170 AT 90 DEGREES

FOR ALUMINIUM CONDUCTORS 120 AT 75 DEGREES AND 135 AT 90 DEGREES