Unit 9: Multi Family Dwelling Service Calculations Flashcards
Analyze NEC 2023 rules, compute service loads for multi-family buildings, and differentiate calculation methods. (25 cards)
Fill in the blank:
When calculating the service entrance conductors for a farm service, the second largest load of the total load, shall be computed at _________.
75%
If the use of multiple grounding connections of driven ground rods results in objectionable current, in compliance with the NEC®, which of the following alterations shall be permitted?
a. Pour salt around each of the ground rods.
b. Use only ground rods of 6 ft. in length.
c. Use a larger grounding electrode conductor.
d. Discontinue one or more grounding or bonding connections.
d. Discontinue one or more grounding or bonding connections.
Fill in the blank:
Installation of information technology equipment remote disconnecting controls shall not be required for critical operations data systems when several conditions are in place including _________.
an approved fire suppression system suitable for the application is in place
What is the term used for electrical equipment or materials to which a symbol has been attached, or other identifying mark of an organization that is acceptable to the authority having jurisdiction?
labeled
Fill in the blank:
Rooms or areas of dwelling units shall be protected by a listed arc-fault circuit interrupter (AFCI), combination type, installed to provide protection of the _________.
entire branch circuit
Fill in the blank:
All receptacles located within at least _________ of a therapeutic tub shall be provided with GFCI protection.
6 feet
Fill in the blank:
When applying the general method of calculations for a dwelling unit having four (4) or more fastened in place appliances, other than electric ranges, dryers, space heating equipment, or air-conditioning equipment, it shall be permissible to apply a demand factor of _________ when sizing the service conductors.
75%
Fill in the blank:
Branch circuits that supply electric signs shall be considered _________ loads for the purposes of calculations.
continuous
Fill in the blank:
Additional services shall be permitted for a single building or other structure sufficiently large to make two (2) or more services necessary if permitted by _________.
special permission by the local authority having jurisdiction
Which of the following statements are true for transformers serving
electric discharge lighting having a rating of more than 1,000 volts?
a. The transformers are not required to be accessible.
b. The transformers should be installed as near to the lamps as practicable to keep the secondary conductors as short as possible.
c. The secondary voltage shall be a maximum of 16,000 volts.
d. The maximum secondary current rating shall not exceed 120 mil amperes.
a. The transformers should be installed as near to the lamps as practicable to
keep the secondary conductors as short as possible.
Assuming the use of THWN copper conductors and terminations rated for 75°C, determine the minimum feeder conductor size when given the following related information:
- 120-volt, single-phase system
- one (1) 30 ampere continuous load
- one (1) 5 ampere non-continuous load
8 AWG
Fill in the blank:
As a general rule, all conductors of a multiwire branch circuit shall originate from the same panelboard, simultaneously disconnect all ungrounded conductors and supply only line-to- _________ loads.
neutral
Fill in the blank:
In general, for newly installed grounded systems, where branch circuits or feeders supply separate buildings or structures, equipment grounding conductors are _________.
required
Given: An underground run of PVC conduit with size 4 AWG conductors is the wiring method used to supply an air-conditioning unit that is protected by an overcurrent protective device rated 60 amperes. What is the minimum size wire-type copper equipment grounding conductor that must be installed in the PVC?
10 AWG
Fill in the blank:
Service conductors installed as open conductors or multi conductor cable without an overall outer jacket shall have a horizontal clearance of not less than _________ from windows that are designed to be open, doors, porches,ladders, stairs or similar locations.
3 ft.
Fill in the blank:
Utilization equipment weighing not more than 6 pounds is permitted to be supported to any box or plaster ring secured to a box, provided the equipment or its supporting yoke is secured with at least two (2) _________ or larger screws.
No. 6
Fill in the blank:
Photovoltaic systems operating at _________ dc or greater between any two conductors shall be protected by a listed PV arc-fault circuit interrupter or other system components listed to provide equivalent protection.
80 volts
Fill in the blank:
In general, for household electric ranges with a rating of 8¾ kW or more,the minimum branch-circuit rating shall be _________.
40 amperes
Fill in the blank:
Each doorway leading into a transformer vault from the building interior shall be provided with a tight-fitting door that has a minimum fire rating of three (3) hours. However, if the transformer vault is protected with an automatic sprinkler system, the minimum construction rating of _________ shall be permitted.
1 hour
Fill in the blank:
Where a 240-volt, single-phase, 5 kW storage-type water heater is located in the basement of a dwelling, and the load-center panel board is located outdoors and not capable to be locked in the open position, disconnect in the basement for the water heater is _________.
required
What is the maximum ampere rating permitted for a 125-volt, single-phase, receptacle outlet having a cord-and-plug connected motor load that does not have individual overload protection?
15 amperes
Fill in the blank:
After all demand factors have been taken into consideration and calculations completed, a one family dwelling with a 120/240-volt, single-phase electrical system has a demand load of 35,000 VA. The minimum sizeTHWN copper ungrounded (line) conductors required for an underground installed service lateral is _________.
2 AWG
What is permitted in the dedicated electrical space above a switchboard or panelboard?
sprinkler protection
Which 3-phase systems would be allowed to be a high-impedance grounded neutral system where a resistor limits the ground-fault current to a low value?
480-volts
