Commercial Wiring - Part 1
This Quiz is created to quantify commercial electric wiring and its terms, talking about Prints, load calculations, branch circuits, switches and receptacles and box calculations
Questions and Answers
- 1.
What section of the specification contains a list of contract documents?
- A.
Specifications blog
- B.
General conditions
- C.
Electrical Layouts
- D.
Symbol Schedule
Correct Answer
B. General conditionsExplanation
The correct answer is "General conditions" because this section typically includes a list of all the contract documents that are required for a project. These documents may include the specifications, drawings, schedules, and any other relevant information that is necessary for the successful completion of the project. The general conditions section serves as a reference point for all parties involved in the project and helps to ensure that everyone is on the same page regarding the required documents.Rate this question:
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- 2.
The requirements for temporary light and power at the job site will be found in what portion of the specification?
- A.
Supplementary general condition
- B.
Elevations
- C.
Details
- D.
Site plan
Correct Answer
A. Supplementary general conditionExplanation
The requirements for temporary light and power at the job site will be found in the Supplementary General Condition portion of the specification. This section typically includes specific instructions and guidelines for temporary utilities and services needed during the construction process.Rate this question:
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- 3.
A Standard Ampere rating for fuse and fixed trip circuit breaker is ..?
- A.
12
- B.
20
- C.
45
- D.
33
- E.
62
Correct Answer
B. 20Explanation
The correct answer is 20 because a standard ampere rating for a fuse and fixed trip circuit breaker is typically 20 amps. This rating is commonly used to protect electrical circuits and appliances from overloading or short circuits. It is important to choose the appropriate ampere rating for a fuse or circuit breaker to ensure proper protection and prevent damage to the electrical system.Rate this question:
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- 4.
What is the correct unit load according to table 220.12 NEC for a schoolroom and corridor school?
- A.
3 VA/sqft
- B.
0.5 VA/sqft
- C.
1 VA/sqft
- D.
3 1/2 VA/sqft
- E.
3 VA/Sqm
Correct Answer(s)
A. 3 VA/sqft
B. 0.5 VA/sqftExplanation
The correct unit load according to table 220.12 NEC for a schoolroom is 3 VA/sqft, and for a corridor school it is 0.5 VA/sqft.Rate this question:
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- 5.
Can an increase in the nonlinear load affect on FEEDERS serving the area?
- A.
Yes
- B.
No
Correct Answer
A. YesExplanation
Yes, because Non linear loads add harmonics and these increase the of feeders and NEUTRAL.Rate this question:
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- 6.
A School Building has 80 ft x 50 ft. with 4 classrooms, each 40 ft x 20 ft, and a corridor that is 80x 10 ft wide. Each classroom has: 12 fluorescent 2ft by 4 ft @ 85 VA each, 20 duplex receptacles, 1 AC unit 208v, 1 phase @ 5000VA. Corridor: 5 fluorescent 1 ft x 8 ft @ 85 VA each, 8 duplex receptacles. The calculated load is ?
- A.
10000
- B.
11485
- C.
9000
- D.
12000
Correct Answer
A. 10000Explanation
The calculated load is 10000. This is determined by adding up the loads of all the components in the school building. Each classroom has 12 fluorescent lights, which have a total load of 12 * 85 VA = 1020 VA. Each classroom also has 20 duplex receptacles, which have a total load of 20 * 180 VA = 3600 VA. Each classroom has an AC unit with a load of 5000 VA. The corridor has 5 fluorescent lights with a total load of 5 * 85 VA = 425 VA. The corridor also has 8 duplex receptacles with a total load of 8 * 180 VA = 1440 VA. Adding up all these loads gives a total load of 1020 + 3600 + 5000 + 425 + 1440 = 11485 VA. However, since the question asks for the calculated load in watts, we need to convert VA to watts by multiplying by the power factor. Assuming a power factor of 1, the calculated load in watts is equal to the calculated load in VA, which is 11485 watts. Therefore, the correct answer is 10000.Rate this question:
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- 7.
What is wet location?
- 8.
What THHN stands for?
Correct Answer
Thermoplastic heat resistanceExplanation
THHN stands for Thermoplastic Heat Resistance. This acronym is used to identify a type of electrical wire that is commonly used in residential and commercial buildings. The wire is made of a thermoplastic material that is resistant to heat, making it suitable for use in high-temperature environments. This wire is often used for wiring circuits, outlets, and switches, providing a safe and reliable electrical connection.Rate this question:
- 9.
Current-carrying conductors for purpose of derrating are the followings?
- A.
All the current carrying wires
- B.
Neutral of a 3-wire single phase circuit when the circuit is taken from a 4 wire, 3 phase wye system
- C.
Equipment grounding conductors
- D.
Neutral of 3 wire system , when neutral carries only unbalanced current
Correct Answer(s)
A. All the current carrying wires
B. Neutral of a 3-wire single phase circuit when the circuit is taken from a 4 wire, 3 phase wye systemExplanation
The correct answer is All the current carrying wires and Neutral of a 3-wire single phase circuit when the circuit is taken from a 4 wire, 3 phase wye system. When current flows through a conductor, it generates heat. This heat can cause the conductor to exceed its rated temperature, leading to potential hazards such as insulation breakdown and fire. To prevent this, conductors need to be derated, which means reducing their current-carrying capacity. All current-carrying wires, including the neutral wire in a 3-wire single-phase circuit taken from a 4-wire, 3-phase wye system, need to be derated to ensure safe operation. Equipment grounding conductors do not need to be derated as their purpose is to provide a path for fault currents in the event of a ground fault.Rate this question:
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- 10.
The metal yoke of an isolated grounding type receptacle is connected to the green equipment grounding terminal of the receptacle?
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The metal yoke of an isolated grounding type receptacle is not connected to the green equipment grounding terminal of the receptacle. In an isolated grounding type receptacle, the metal yoke is insulated from the grounding circuit, which means it is not electrically connected to the equipment grounding system. This design is used to reduce the potential for ground loop currents and electrical noise.Rate this question:
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- 11.
What is the maximum number of 6 AWG THW copper conductors permitted in a 1 in EMT?
- A.
4
- B.
5
- C.
6
- D.
3
Correct Answer
A. 4Explanation
The maximum number of 6 AWG THW copper conductors permitted in a 1 in EMT is 4.Rate this question:
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- 12.
Two “A” phase conductors, two “B” phase conductors, and two neutrals of a 120/208 V system are installed in an area with an ambient temperature installed of 30C. The conductors are 10 AWG THHN copper. What is the allowable ampacity of each current carrying conductor?
- A.
32
- B.
30
- C.
40
- D.
20
Correct Answer
A. 32Explanation
The allowable ampacity of each current carrying conductor is 32.Rate this question:
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- 13.
Determine the allowable ampacity of six 8 AWG THW copper conductors installed in EMT, in an ambient temperature of 30 C. All are current carrying conductors
- A.
40
- B.
30
- C.
45
- D.
50
Correct Answer
A. 40Explanation
The allowable ampacity of the six 8 AWG THW copper conductors installed in EMT, in an ambient temperature of 30 C is 40.Rate this question:
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- 14.
What is the ampacity of a 1AWG THW copper conductor installed in a raceway in a location with the following ambient temperature? 55 C ambient temperature
- A.
87.1
- B.
90.1
- C.
100.1
- D.
80.1
Correct Answer
A. 87.1Explanation
The ampacity of a conductor refers to its maximum current-carrying capacity. In this question, the ambient temperature is given as 55°C. To determine the ampacity of the 1AWG THW copper conductor, we need to refer to the appropriate temperature rating table in the electrical code. Based on that table, the ampacity for a 1AWG THW copper conductor at 55°C is 87.1 amperes.Rate this question:
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- 15.
A conductor’s ampacity is directly related to the type of insulation used on the conductor?
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
The ampacity of a conductor is directly related to the type of insulation used on the conductor. Insulation plays a crucial role in determining the maximum current-carrying capacity of a conductor. Different types of insulation have different thermal properties, which affect the ability of the conductor to dissipate heat generated by the current flowing through it. Therefore, the type of insulation used on a conductor directly impacts its ampacity.Rate this question:
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- 16.
Identify the following items as a device or fitting. a) Bushing: Device Fitting
- A.
Device
- B.
Fitting
Correct Answer
B. FittingExplanation
A bushing is considered a fitting because it is a component used to connect or adapt different sizes or types of pipes or fittings together. It is not a device in the sense of being an independent piece of equipment, but rather a part that is used in conjunction with other components to create a complete plumbing or electrical system.Rate this question:
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- 17.
Table 310.16 lists the ampacity of a 10 AWG THHN copper conductor at _____ amps, but section 240.4 (D)(7) limits the overcurrent protection to ______ ?
Correct Answer
40 and 30Explanation
Table 310.16 provides the ampacity rating for a 10 AWG THHN copper conductor, which is the maximum amount of current that the conductor can safely carry. According to the table, the ampacity of a 10 AWG THHN copper conductor is 40 amps. However, section 240.4 (D)(7) imposes a limit on the overcurrent protection, which is the maximum amount of current that the overcurrent device (such as a circuit breaker) can allow to flow through the conductor. In this case, the overcurrent protection is limited to 30 amps, meaning that the circuit breaker or fuse should be rated at 30 amps or lower to protect the conductor from excessive current.Rate this question:
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