Lessons 11-13
The general requirements for grounding and bonding for both grounded and ungrounded systems can be located in section ___.
250.4
Performance requirements for grounded electrical systems are provided in NEC ____.
250.4(A)
Where A DC system, other than a three wire balancer set, has a 250 Copper Kcmil neutral conductor connected, the grounding electrode conductor shall not be smaller than ___.
259 Kcmil copper
If overcurrent protection is NOT provided where the conductors originate, at a grounded separately derived system source supplying a separate building or structure, the installation must comply with ____.
250.30(A)
Which of the following systems is not required to be grounded because if it is grounded, the phase to ground voltage would exceed 150 volts? - 120 volt single phase - 480 volt 3 phase delta system - 120/240 single phase 3 wire system - 50 volt single phase
480 volt 3 phase delta system
For a three phase, three wire, corner grounded, separately derived system that has 500 Kcmil copper ungrounded derived phase conductors, the grounded conductor must be no less than ___.
500 Kcmil copper.
If the grounding electrode for a separate building or structure is a single ground rod as permitted in 250.53(A)(2) Exception, the maximum size grounding electrode conductor required is ___ copper, regardless of the size of the feeder supplying the building or structure served.
6 awg
Where the grounding electrode for a separate building or structure is a single ground rod, what is the maximum size copper grounding electrode conductor required if the feeder supplying the separate building or structure is sized at 2500 amps?
6 awg
The grounding electrode conductor for a separately derived system is required to be connected to the grounded conductor where the ____ is installed.
6 awg copper
Name something that is not an example of a separately derived system.
An auto transformer former with a grounded conductor common to both the primary and secondary.
True or false Where a delta connected system over 1000 volts is used to supply portable or morning equipment, a neutral point and system neutral is not permitted to be derived for grounding purposes.
False - not required
True or false: the system bonding jumper is permitted to extend beyond the enclosure where it originates.
False, it must remain in the same enclosure.
The size of a DC system bonding jumper has to be no less than the system grounding electrode conductor based on 250.66. True or false?
False. 250.166
A ________ includes all circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch circuit overcurrent device.
Feeder
Metal water piping and structural metal framing that exists in the area served by a separately derived system has to be bonded to the grounded conductor of that separately derived system and ___ is used to size this bonding jumper or conductor.
Table 250.66
True or false - a connection to ground through a grounding electrode system is generally require at separate buildings or structures to establish a reference to ground at that location.
True
True or false: In general, the grounding electrode for a separately derived system must be as near as practice of all, preferably. In the same area, and must be the nearest of either a metal water pipe electrode or a structural metal electrode, unless neither of the above electrodes are not available, in which case an electrode according to 250.52 A must be installed.
True
If a separately derived system has 600 Kcmil copper secondary ungrounded phase conductors, what is the minimum size required for the system bonding jumper (copper, wire type).
1/0 awg
Which of the following electrical systems is required to be grounded? 240 volt, 3 phase, 3 wire, delta connected 120 volt, single phase system 480 volt, 3 phase 3 wire delta connected 2300 volt 3 phase 3 wire delta connected 4600 volt 3 phase 3 wire delta connected
120 volt single phase system
What size grounding electrode conductor is required for a separately derived system with 4/0 AWG copper ungrounded derived phase conductors if the grounding electrode is a metal building frame electrode in accordance with 250.52 A2 ?
2 awg copper
If the grounding electrode conductor for a separate building or structure is a sole connection to a concrete-encased electrode, the maximum size required is a __ Awg copper conductor.
4
Name two locations that are permitted for installing the system bonding jumper of a separately derived system.
The first system disconnecting means enclosure, the source enclosure
A separately derived system is required to be grounded in accordance with 250.30 A and is located 50 feet from a building structural metal electrode and 100 feet from a metal water pipe electrode. What is required to be used to meet the minimum requirements in the NEC?
The system shall be grounded by connection to the metal building frame electrode.
A _____ equipment grounding conductor is the minimum size required for a 1000 ampere feeder supplying a separate building or structure. (State the # of awg and material.. Aluminum or copper)
4/0 awg aluminum
The grounding electrode conductor for a single separately derived system is required to be sized using which NEC table?
Table 250.66
The size of the grounding electrode conductor for a separate building or structure shall generally NOT be smaller than the sizes provided in ___.
Table 250.66 based on the size of the largest ungrounded conductor of the feeder
True or false: If the overcurrent device is located on the generator outside that supplies a separate building or structure, then the feeder is on the load side of an overcurrent device. In this case, the EGC with the feeder is sized based on the requirements in 250.102(D).
True
True or false: In health care facilities, those isolated powered circuits in hazardous (classified) inhalation anesthetizing locations are required to be supplied by an isolation transformer or other ungrounded source and are NOTE permitted to be grounded.
True
True or false: the neutral of a high impedance grounded neutral system is required to be fully insulated and no equipment grounding or equipment bonding connections are permitted on the supply side of the impedance device
True
Not connected to ground or to be a conductive body that extends the ground connection best defines which of the following code terms: not grounded, impedance grounded, ungrounded, resistance grounded?
Ungrounded
The grounding electrode conductor for a single separately derived system in accordance with ___ must be sized at a Minimum in accordance with the sizes ___ based in the circular mil area of the phase conductors.
250.30(A)(5)/table 250.66
Systems operating at 50 volts to 1000 volts are required to be grounded under which of the following conditions? - if the system can be grounded so that the max voltage to ground on the ungrounded conductors does not exceed 150 volts - if the system is in 3 phase, 4 wire and is wye connected and the system neutral conductor is used as a circuit conductor - if the system is a 3 phase 4 wire and is delta connected in which the midpoint of one phase winding is used as a circuit conductor - any of the above
Any of the above
Identify the three methods for connecting the grounding electrode conductor taps to the common grounding electrode conductor are at an accessible location.
Listed connector for grounding and bonding equipment, exothermic welding, listed connections to a 0.25 x 2" copper or aluminum BuSbar, irreversible crimps
The ___ is the conductor connected to the neutral point of a system that is intended to carry current under normal conditions.
Neutral conductor.
Is it ever Code compliant to install a feeder to a separate building or structure without an equipment grounding conductor or supply side bonding jumper?
No
Which part of article 250 provides the specific requirements for system grounding?
Part 2
According to NEC, that which is built or constructed best defines a _____.
Structure
True or false: If a generator is installed on a premises wiring system, it must be grounded as a separately derived system if there is a switching action in the grounded conductor through the transfer switch.
True
True or false: If the overcurrent device is NOT located on the generator outside that supplied a separate building or structure, then the feeder is on the load side of an overcurrent device. In this case, the EGC with the feeder is sized based on the requirements in 250.102(C)
True
True or false: The disconnecting means installed for a feeder supplying a separate building or structure is generally required to be suitable for use as service equipment.
True
Secondary circuits for underwater lighting installed in swimming looks or spas are NOT permitted to be grounded under which conditions?
Where listed for swimming pool or spa use, and either where the transformer incorporates a system of double insulation between the primary and secondary windings OR where the transformer is an isolation type with a grounded metal barrier between the primary and secondary windings
** Is a grounding electrode system required for each building or structure served by a feeder?
Yes
Where more than one separately derived system is grounded to a common ground in the electrode conductor, the common grounding electrode conductor shall be sized at not less then ____ copper or ___ aluminum.
3/0 awg/ 250 Kcmil
Which of the following AC systems is permitted to be grounded, but not required to be grounded?
480 volt delta, 3 phase system
What is the minimum size required for the ground and neutral conductor of a separately derived system where there is no load on the neutral conductor?
Not smaller than the values in table 250.66, based on the size of the largest ungrounded derived fees conductor connected to the system
Where the grounded conductor is used for grounding in accordance with the provision of 250.32(B)(1) exception, the size of the grounded conductor shall not be smaller than the larger of which 2 code provisions.
That required by 220.61, that required by 250.122
Define a branch circuit
The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
Which of the following is not considered an effective ground fault current path? Equipment grounding conductor (wire type) , earth, building steel, equipment grounding conductor (rigid metal conduit)
Earth
Where a system is grounded, the grounded (usually neutral) conductor(s) in sizes 4 awg and larger than 6 awg must be identified generally by which of the following means? - continuous white or gray insulation along the entire length of the conductor - three continuous white stripes on insulation other than green for the entire length of the conductor - identification at the time of installation by a distinctive white or gray marking at the termination of the conductor, the marking has to encircle the conductor. - any of the above
Any of the above
Where separately derived system is installed outside of building or structure and supplies, a grounding electrode connection is NOT required at the source location. True or false?
False.. It IS required.
A High impedance grounded neutral system rated 480 volts to 1000 volts is only permitted under which of the following conditions? - There are no conditions of maintenance and supervision that ensures only qualified persons service installation. - ground detectors are not installed on the system - line to neutral loads are served by the system. - all of the above - none of the above
None of the above
The __ is a conductor installed on the supply side of a service or within a service equipment enclosure(s), or for a separately derived system that ensures the required electrical conductivity between metal parts required to be electrically connected.
Supply side bonding jumper
Separately derived systems supplied by transformers that have a primary voltage eating less than 1000 volts are not required to be grounded if which conditions are met?
Systems used exclusively for control circuits, where conditions of maintenance and supervision ensure that only qualified persons service the installation, where continuity of control power is required, systems that are not required to be grounded in accordance with the requirements of 250.20(b).
True or false: where a building is supplied by an ungrounded system, the feeder from the ungrounded system must include equipment grounding conductor or supply side bonding jumper with the conductors to the building disconnecting means and it must be connected to the disconnecting means enclosure as well as to the grounding electrode conductor.
True
True or false: where a system bonding jumper is a wire type, it is sized using table 250.66 or the 12.5% rule based on the size of the largest ungrounded derived phase conductor(s) or the total circular mil (cm) area of all conductors connected to any one ungrounded phase at the source.
True
Using the installation described in question 30, what is the minimum size supply side bonding jumper (copper) required with a 400 ampere feeder from an outdoor generator to the building disconnecting means? Note: the largest ungrounded phase conductor supplied by the generator is 750 Kcmil aluminum.
3/0 awg
If the voltage of the secondary side of the transformer is less than ____ and the voltage of the primary side of the transformer exceeds ____ to ground, the secondary side shall be grounded.
50 volts and 150 volts
List 8 types of grounding electrodes permitted by 250.52 A.
1. Metal underground water pipe. 2. Metal frame of the building or structure. 3. Concrete encased electrode. 4. Ground ring. 5. Rod and pipe electrode. 6. Other listed electrodes. 7. Plate electrodes. 8. Other local metal underground systems or structures.
An AC system operating at less than 50 volts is required to be grounded under which conditions?
1. Where supplied by transformers if the supply system exceeds 150 volts to ground 2. Where supplied by transformers, if the supply system is ungrounded 3. Where installed outside as overhead conductors
A 400 amp feeder made up of four 600 Kcmil copper conductors and a single size 3 awg copper equipment grounding conductor is installed to supply a separate building. The only grounding electrode present is structural steel for the building. What is the min size grounding electrode conductor required for the building served?
1/0 awg copper
If PVC conduit is installed for an 800 amp feeder supplying a separate building, what is the minimum size wire type copper equipment grounding conductor required to be installed with the feeder conductors?
1/0 awg copper
250.188 required grounding all portable or mobile high voltage equipment that is supplied from an AC system of ____ and over.
1000 volts
True or false: Ungrounded systems are equites to be marked "ungrounded system" at the source or first disconnecting means of the system and the marking must be of sufficient durability for the environment in which it is installed.
True
True or false: Where a structure such as a light pole base in a parking lot is supplied by a single branch circuit, a grounding electrode is permitted to be installed but not required.
True
True or false: Where no grounding electrode is present at a separate building or structure served by a feeder a grounding electrode in accordance with 250.50 is required to be installed.
True
Where the derived phase conductors (secondary conductors) from a transformer separately derived system are sized at 500 kcmil copper and installed in flexible metal conduit from the transformer to a panelboard, what is the minimum size copper supply-side bonding jumper required to be installed in the flexible metal conduit?
1/0 awg
A separately derived system is installed and has 4/0 AWG copper XHHW conductors installed from the secondary of the system to a 225 amp panel board what is the minimum size copper bonding jumper for a metal water piping system that serves the same area that is served by the separately derived system?
2 awg
If a generator separately derived system has an overcurrent protection provided at the generator, what table is used to size the equipment grounding conductors installed with the supply conductors of the generator to the transfer equipment enclosure or first disconnecting means enclosure?
250.122
The minimum size required for the grounding electrode conductor installed for an ungrounded DC system must not be smaller than required in ___.
250.166
The system bonding jumper for a separately derived system in size in accordance with ____.
250.166
NEC _____ provides the requirements for grounding of electrical systems and equipment at buildings or structures that are supplied from a feeder or branch circuit.
250.32
If overcurrent protection is provided where the inductors originate, at a grounded separately derived system source supplying a separate building or structure, the installation must comply with ____.
250.32(B)(1)
When an ungrounded source supplies separate buildings or structures by a feeder, the requirements in ___ apply.
250.32C, 250.50, 250.32E
What section of article 250 requires that all electrodes present at any building or structure served be bonded together to form a grounding electrode system?
250.50
Which of the following conditions is not required to qualify for installation and use of a high impedance grounded neutral system?
Continuity of power is required
True or false: Where supplying portable or mobile equipment, electrical systems of 1000 volts and greater must not be grounded.
False
Choose from the following options: underground metal water pipe, structural metal building frame electrode, ground rods. Select all of the electrodes that must be used to form a grounding electrode system for a building or structure served by a feeder or branch circuit.
Any present must be used.
If a generator has 1200 amp overcurrent device installed at the generator set, and a minimum size of ___ copper is required for the EGC installed in conduit of a parallel set of 4 inch PVC conduit routed from the generator to the first system overcurrent device enclosure.
3/0 awg
An exception applying only to existing premises wiring systems permits the continued use of the grounded conductor for grounding at separate buildings under which restrictive conditions?
1. An ECG is not included with the supply circuit to the separate building or structure. 2. There are no common electrically continuous metallic paths between the feeder source and the destination at the building or structure served. 3. Ground fault protection of equipment is not provided on the supply side of the feeder.
What is the minimum size copper bonding jumper required for a metal water piping system in a building or structure supplied by a 400 amp feeder that includes 600 kcmil circuit conductors?
1/0 awg
Where a generator separately derived system is installed and there is no overcurrent device at the generator, what is the minimum size required for the supply-side bonding jumper (copper) installed with the ungrounded derived phase conductors to the first disconnecting means enclosure if the ungrounded phase conductors are at 750 Kcmil aluminum?
3/0 awg
A/n ____ is an intentionally constructed, low impedance electrically conductive path designed and intended to carry current under ground fault conditions from the point of grounding on a wiring system to the electrical supply source a d one that facilitates the the operation of the overcurrent device or ground fault detectors on a high impedance system.
Effective ground fault current path
True or false: If a feeder to a separate building or structure is installed in rigid metal conduit, the conduit is not permitted to serve as the required grounding conductor.
False
True or false: In general the one toon of the grounding electrode conductor to the grounded conductor of the separately derived system is required to be made at a different location then the bonding jumper connection.
False (the same location)
If the transfer switch for generator system switches the grounded neutral conductor the generator has to be grounded as a separately derived system in accordance with 250.30B. True or false?
False. It includes a switching action.
The _____ for an ungrounded system is required to be connected tot the system as close as practicable to where the system receives its supply.
Ground detection sensing equipment
A/n ___ is a premises wiring system whose power is derived form a source of electric energy or equipment other than a service. Such systems have no direct connection from circuit conductors of one system to circuit conductors of antoher system other than connections through the earth, metal enclosures, metallic raceways, or equipment grounding conductors.
Separately derived system
A/n ___ is the connection between the grounded circuit conductor and the supply side bonding jumper, or the equipment grounding conductor, or both, at a separately derived system.
System bonding jumper