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1. |
250.35 This is a new section added to address the grounding of permanently installed generators. Part A covers separately derived systems where the neutral or grounded conductor is transferred using a transfer switch as shown in the diagram below. Part B covers non separately derived systems where the neutral or grounded conductor is not transferred by the transfer switch.
The equipment grounding conductor on the line side of the generator overcurrent device is sized using the rules in 250.102(C) that uses Table 250.66. On the load side of the generator the equipment grounding conductor is sized using Table 250.122 where the rating or setting of the overcurrent device is used to select the size of the EGC.
Question: A generator overcurrent device has a circuit breaker set at and rated at 400 amperes and the conductors from the generator to this device are 500 KCMIL, which Table would be used to select the size of equipment grounding conductor that go between the generator and the enclosure for the circuit breaker (supply or line side)?
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a)
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Table 250.66
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b)
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Table 250.122
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2. |
250.35 This is a new section added to address the grounding of permanently installed generators. Part A covers separately derived systems where the neutral or grounded conductor is transferred using a transfer switch as shown in the diagram below. Part B covers non separately derived systems where the neutral or grounded conductor is not transferred by the transfer switch.
The equipment grounding conductor on the line side of the generator overcurrent device is sized using the rules in 250.102(C) that uses Table 250.66. On the load side of the generator the equipment grounding conductor is sized using Table 250.122 where the rating or setting of the overcurrent device is used to select the size of the EGC.
Question: A generator overcurrent device is a circuit breaker set at and rated at 400 amperes and the conductors from the generator to this device are 500 KCMIL, which Table would be used to select the size of equipment grounding conductor on the load side of the circuit breaker?
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a)
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250.66
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b)
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250.122
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3. |
250.52(A)(3) Revision allows concrete encased electrodes to be either vertical or horizontal.
Concrete Encased Electrodes
An electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1.2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective.
NEW sentence added. Where multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.
Question: A concrete encased electrode shall be encased in at least _____ inches of concrete and shall be at least _______ feet long.
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a)
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20, 2
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b)
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4, 10
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c)
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2, 20
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4. |
250.52(A)(6) Other Listed Electrodes
This is a new section that gives permission for the use of other listed electrodes.
These electrodes are listed to UL standard 467 and are provided by various manufacturers.
Question: The 2008 NEC gives permission to use other _____ electrodes.
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a)
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identified
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b)
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listed
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c)
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approved
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5. |
250.64(D) Service With Multiple Disconnecting Means Enclosures. This section has been revised to clarify how grounding electrode conductors are sized for services with multiple disconnecting means. See the diagram below for an explanation.
Question: When a service has multiple disconnecting means as permitted in 230.71(A) grounding electrode conductors to each individual disconnecting means shall be based on Table _______ based on the size of the service entrance conductors supplying the individual disconnecting means.
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a)
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250.66
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b)
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250.102
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6. |
250.68(A) and Exception No. 2 Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrode
This section has been revised to make it clear that when a bolt and nut is used to attach a grounding electrode compression connector under fire proofed structural metal it does not have to be accessible.
Question: Exothermic or irreversible compression connections used at terminations, together with the mechanical means used to attach such terminations to fireproofed structural metal whether or not the mechanical means is reversible, shall not be required to be ________ .
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a)
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readily accessible
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b)
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accessible
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c)
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visible
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7. |
Section 250.94 Bondidng for Other Systems has been completely revised and incorporates changes in Chapters 7 and 8 that now require a Intersystem Bonding Termination (IBT). Article 100 defines IBT as a device that provides a means for connecting communications system(s) grounding conductor(s) and bonding conductor(s) at the service equipment or the disconnecting means for buildings or structures supplied by a feeder or branch circuit. The size of the conductor used to connect the IBT to the power service grounding electrode system must not be smaller than No. 6 AWG copper.
Question: The size of the required conductor for connecting the power service grounding electrode system to the IBT is ______________________ minimum.
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a)
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No. 14 AWG copper
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b)
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No. 6 AWG copper
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c)
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No. 4 AWG copper
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8. |
250.112(I) Remote-Control, Signaling, and Fire Alarm Circuits
NEW requirement added: Equipment supplied by Class 1 circuits shall be grounded unless operated at less than 50 volts.
Question: If a 120 volt Class 1 circuit supplies power to a damper motor then the damper motor is required to be ____________ .
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a)
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isolated
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b)
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grounded
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c)
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ungrounded
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9. |
250.118 Types of Equipment Grounding Conductors
A new Fine Print Note has been added. FPN: For effective ground-fault path see 250.2 definition.
The phrase "listed for grounding" used for flexible metal conduit and for liquidtight flexible conduit have been changed to "listed fittings" since fittings are used for both bonding and grounding.
Question: Listed fittings used with flexible metal conduit and liquidtight metal conduit are listed for both grounding and __________ .
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a)
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low impedance
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b)
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bonding
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c)
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low resistance
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10. |
250.119 Exception. This new exception allows the use of green insulated conductors for use other than grounding.
Exception: Power-limited, Class 2, or class 3 circuit cables containing only circuits operating at less than 50 volts shall be permitted to use a conductor with a green insulation for other than equipment grounding purposes.
Question: A ______ insulated conductor in a cable used for a Class 2, 24-volt circuit can be used to carry power to a damper motor.
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a)
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green
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b)
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red
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c)
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blue
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d)
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yellow
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e)
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Any of the above
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