Article 240 - Overcurrent protection
a standard fuse is needed to provide overcurrent protection for 277/480 volt feeder with an ampacity of 1100 amps. if the feeder does not supply motor loads, which of the following fuses may be used?
1000 amps rated at 1000 volts 240.4C
a 4600 volt, 4/0 three conductor copper cable is in insulated conduit in air. what is the maximum allowable rating of a circuit breaker used to protect the ungrounded conductors?
1200 amps 360.60C(75) and 240.101(A) calcs: 255A x 6 = 1530A 240.101A shall not exceed 1200A
OCPDs shall not be located?
240.24
a 7200 volt, 2/0 three conductor aluminum cable is direct buried. what is the maximum allowable rating of a fuse used to protect the ungrounded conductors?
600 amps 360.60C(84) and 240.101(A) calcs: 210A x 3 = 630A 240.101A shall not exceed 600A
a 2500 volt, 2/0 three conductor copper cable is direct buried. what is the maximum allowable rating of a fuse used to protect the ungrounded conductors?
700 amps 360.60C(83) and 240.101(A) calcs: 260A x 3 = 780A 240.101A shall not exceed 700A
a fuse is protecting conductors which are supplying a continuous lighting load. the fuse is not listed for continous duty. what is the maximum load that this circuit can supply?
80% of the fuse rating (210.20A)
240.24
OCPDs shall be readily accessible...handle shall not exceed 6ft 7 in above working platform when at highest position
a 120/240 volt, 2-wire branch circuit supplies a 30 amp noncontinuous nonmotor load. what type of overcurrent device can be used to protect the branch circuit?
a 30 amp fuse installed in series with the underground conductor (240.8, 240.9,240.4B2,240.15A)
240.22
an OCPD cannot be connected in series with any intentionally grounded conductor
circuit breakers used for switches in 120 volt and 277 volt flourescent lighting circuits shall
be marked SWD (240.83D
240.83(D)
breakers should be durable ad visibly marked with their ampere rating. if the breaker is used as a switch in 120 or 277 volt fluorescent lighting circuits, they shall be listied for switching duty and marked SWD or HID
240.83(C) for breakers
breakers with an interrupting rating other than 5000 amps shall have the rating marked on the breaker
edison based plug fuses cannot be used for the following except
circuits over 20 amps (240.51)
240.4 states that
conductors other than flexible cords and cables shall be protected against overcurrent in accordance with ampacities specified in section 310.15
240.40
disconnecting means shall be provided on the supply side of all fuses in circuits of over 150 volts
240.51
edison base fuses shall be classified at not over 125 volts and 30 or less amps and used for replacement only
240.101(A)
feeders - a fuse shall not exceed three times the ampere rating of the conductor. a breaker or electronically actuated fuse shall not exceed six times the ampere rating of the conductor
240.60(C) for fuses
fuses with interrupting rating other than 10,000 amps shall have the rating marked o the fuse barrel or on a label attached to the barrel
210.8 covers
ground fault protection for personnel in dwelling units
240.4 (B)
if a conductor ampacity doesnt correspond to a standard OCPD rating, the next higher standard device is permitted if the rating does not exceed 800amps and the conductor isnt part of a multi-outlet branch circuit
240.8
overcurrent devices shall not be field connected in parallel
240.9
thermal devices shall not protect conductors against overcurrent due to shorts or ground faults. thermal devices are used to protect motor branch circuit conductors
what section of the codebook would be used to determine OCPD for GCFIs in dwellings?
210.8A6
an OCPD is connected in series with a grounded conductor of a 3 wire branch circuit. the device must?
240.22(1) - open all conductors in the circuit and allow no pole to operate independently
a #8 AWG copper NMS cable is supplying a household electric range. what is the maximum rating of the overcurrent device permitted to protect the cable?
40 amps 334.80, Table 310.15(b)(16) and 240.4
240.50(A)
plug fuses and fuseholders are limited to use in circuits not exceeding 125 volts between two conductors unless the circuit has a grounded conductor and no conductor at over 150 volts to ground
the screw shell of a plug type fuse holder shall be connected to?
the load side of the circuit (240.50e)
240.21
the overcurrent protection device shall be connected at the point where the conductor receives it supply
240.50(E)
the screw shell of a plug type fuseholder shall be connected to the load side of the circuit
