Unit 8: Single Family Dwelling Service Calculations Flashcards
Apply NEC residential service calculation steps, justify service size selection, and validate compliance with NEC requirements.
Fill in the blank:
An acceptable color for conductors intended for use as ungrounded conductors is ________.
orange
Fill in the blank:
A metal underground water pipe is permitted for use as a grounding electrode where the water pipe is in direct contact with the earth for at LEAST ________ or more.
10 feet
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For low-voltage lighting systems operating at 30 volts or less, the output circuits of the power supply are to be rated for not more than ________ under all load conditions.
25 amperes
Where a 12-kW portable generator is used for temporary wiring on a construction site, which single-phase, 125-volt receptacle outlets are mandated to provide ground-fault circuit-interrupter protection for personnel?
All 15-ampere, 20-ampere, and 30-ampere rated
receptacles.
Fill in the blank:
An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment or earth is referred to as a ________ in the NEC®.
ground-fault
Fill in the blank:
Where GFCI protection is not provided, ceiling suspended (paddle) fans are not permitted to be located ________.
over a spa or hot tub, less than 12 ft. above the maximum water level
Which of the following underground installed buried metal pipes is approved for use as a grounding electrode?
I. A water pipe, in direct contact with the earth for 8 ft.
II. A gas pipe, in direct contact with the earth for 30 ft.
neither I nor II
Fill in the blank:
For an overhead type motor fuel dispensing device located at a service station or a convenience store, the space within the dispenser enclosure shall be classified as a ________ location.
Class I, Division 1
Disregarding exceptions, and assume the modification of the value you select is not necessary, determine the MAXIMUM trip setting permitted for the overload devices used to protect a 3-phase, 10 hp, 208-volt, continuous-duty motor with a FLA of 28 amperes and a temperature rise of 46°C marked on the motor nameplate.
32.2 amperes
Nameplate FLA rating – 28 amperes x 115% = 32.2 amperes
The neutral conductor is ALWAYS:
connected to the neutral point of an electrical system.
Fill in the blank:
The overcurrent protection for feeders and branch circuits that serve electric vehicle supply equipment, shall be sized at not less than ________ of the maximum load of the electric vehicle supply equipment.
125%
Fill in the blank:
Stationary ac motors require the ________ where installed in a Class I, Zone 2 atmosphere that is considered a hazardous or classified location.
frame of the motor shall be grounded
Given: A rigid metal conduit (RMC) originates in an area that is unclassified, then passes through a Class I, Division 1 area, and finally terminates in a panelboard located in an unclassified area. The RMC is without any connections or fittings when passing through the Class I, Division 1 area or within a foot on either size of the boundary of the Class I, Division 1 location. How many seal-off fittings are required in this conduit run?
none
Given: A 3-phase, 240-volt delta system is balanced with a 15 kVA load per phase (45,000 VA total load). What is the line current in amperes?
108.2 amperes
I = 45,000 VA/240 x 1.732
= 45,000/416
= 108.2 amperes
Fill in the blank:
Generally, where switches or circuit breakers are used as the main disconnecting means for a building service, they shall be installed such that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than ________ above the floor or working platform
6 feet, 7 inches
Fill in the blank:
The service equipment for a mobile home shall have an ampere rating of not less than ________ at 120/240-volts, single-phase.
100 amperes
What is the required characteristic of an intersystem bonding termination?
It shall be connected to the meter enclosure only, with a minimum size 8
AWG conductor.
Fill in the blank:
For 120-volt, 15- and 20-ampere branch circuits, the rating of any one (1) cord-and-plug connected utilization equipment not fastened in place shall not exceed ________ of the branch circuit ampere rating.
80%
Fill in the blank:
The National Electrical Code® requires ventilation of a battery room where batteries are being charged to prevent ________.
an accumulation of an explosive mixture
Where a building has a service rated at 1,200 amperes and multiple driven ground rods are used as part of the grounding electrode system, what is the MINIMUM size copper conductor that may be used to bond the ground rods together.
6 AWG
Fill in the blank:
All 15- and 20-ampere, 125- and 250-volt, non locking receptacles located in a wet location shall be listed ________ type.
weather-resistant
Fill in the blank:
Where liquidtight flexible metal conduit (LFMC) is used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation ________.
an equipment grounding conductor shall be installed
Fill in the blank:
Luminaires shall be installed so that adjacent combustible material is not subjected to temperatures in excess of ________.
90°C
Fill in the blank:
A household gas furnace with a one (1) hp motor protected with a circuit breaker accessible to the user, does not require a disconnecting means if ________.
provided with a unit switch that disconnects all ungrounded conductors
