Unit 3: Cooking Equipment & Appliance Demand Loads Flashcards
Understand NEC demand factors, apply them to real-world scenarios, and compare standard vs. demand load calculations.
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A listed ________ shall be installed in or on all emergency systems switchboards and panelboards.
Surge-protective device (SPD)
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In general, where a cable bus system is rated 95 amperes, the MAXIMUM allowable rating of the overcurrent device that may be used to protect the cable bus conductors is ________.
100 amperes
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A feeder tap less than 25 feet in length is not required to have overcurrent protection if the ampacity of the tap conductors is not less than ________ of the rating of the overcurrent device protecting the feeder conductors.
one-third
Given: A flexible metal conduit (FMC) to be installed will contain three (3) size 400 kcmil THWN copper conductors and one (1) size 250 kcmil copper conductor. Where the FMC is more than 24 inches long, what MINIMUM trade size FMC is permitted for this installation?
3 in.
250 kcmil THWN – 0.3970 sq. in. x 1 = 0.3970 sq. in.
400 kcmil THWN – 0.5863 sq. in. x 3 = 1.7589 sq. in.
Total = 2.1559 sq. in.
A trade size 3 in. FMC with a permitted fill area of 2.827 sq. in. @ 40% fill should be selected from Table 4 of Chapter 9.
In a hospital, what MUST be provided at a patient bed location used for general care (Category 2) spaces?
- one branch circuit from the normal system
- one branch circuit from the critical branch of the essential electrical system
- “hospital-grade” receptacles
When an electrical service is required to have a grounded conductor present, what is the smallest grounded conductor permitted for an electric service using size 1000 kcmil copper ungrounded conductors installed in a single raceway?
2/0 copper
Determine the MINIMUM number of 20-ampere, 277-volt, general-lighting branch circuits required for a 150,000 square foot retail department store where the actual connected load is 400 kVA of fluorescent lighting; consider circuit breakers of this size are not rated for continuous use.
91
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Where a 2-gang box contains two (2) single-pole switches, unless the box is equipped with permanently installed barriers, voltage between the adjacent switches shall not be in excess of ________.
277 volts
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Where electrical metallic tubing (EMT) is installed under metal-corrugated sheet roofing decking, a clearance of at LEAST ________ must be maintained between the top of the tubing and the surface of the roof decking.
1 ½ in.
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Fluorescent luminaires installed MORE than ________ above the floor located outside of the patient care vicinity in a hospital, shall not be required to be grounded by an insulated equipment grounding conductor.
7 ½ feet
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Where nonmetallic conduit is used to enclose conductors supplying a wet-niche luminaire located in a permanently installed swimming pool, a size ________ insulated copper grounding conductor shall be installed in the conduit, unless a listed low-voltage lighting system not requiring grounding is used.
8 AWG
Fill in the blank:
The ampacity of phase conductors from the generator terminals to the first overcurrent device shall not be less than ________ of the nameplate current rating of the generator where the design of the generator does not prevent overloading.
115%
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In Class II, Division 1 locations, an approved method of connection of conduit to boxes or cabinets is ________.
threaded bosses
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The upward discharging vent of an underground fuel tank of motor fuel dispensing facilities is classified as a Class I, Division 1 location WITHIN ________ of the open vent, extending in all directions
5 feet
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Conductors between the controller and the diesel engine of a fire pump are required to be ________
104 deg. C rated
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The ampacity of a size 750 kcmil XHHW aluminum conductor when there are six (6) current carrying conductors all of the same size and insulation in the raceway, installed in a dry location where the ambient temperature will reach 22 deg. C is ________.
361.92 amperes
Size 750 kcmil AL ampacity (before derating) = 435 amperes
435 amps x 1.04 (temp. correction) x .8 (adjustment factor) = 361.92 amperes
Fill in the blank:
Where multiple driven ground rods are used to form the grounding electrode system, in order to maintain an effective grounding electrode system, they shall not be spaced less than ________apart.
6 feet
According to the NEC®, flat conductor cable (FCC) is permitted to be used for:
I. general-purpose circuit conductors.
II. appliance circuit conductors
both I and II
Determine the MINIMUM size USE aluminum cable permitted for use on an underground 120/240-volt, single phase, service for a small office building that has a total load of 23,600 VA after all demand factors have been taken into consideration. Consider all conductor terminations are rated for 75 deg. C.
1 AWG
I = P ÷ E I = 23,600 VA ÷ 240 volts = 98.33 amperes
Size 1 AWG AL USE cable with an ampacity of 100 amperes should be selected from Table 310.16.
Fill in the blank:
Without overcurrent protection at the tap, the MAXIMUM horizontal length of feeder tap conductors in a high-bay manufacturing building over 35 feet high at walls shall be ________.
25 feet
Where an apartment complex has a connected lighting load of 205.4 kVA, what is the demand load, in kVA, on the ungrounded service-entrance conductors? Consider each apartment unit has provisions for cooking by tenants and apply the general (standard) method of calculation for dwelling units.
65.3 kVA
Total lighting equals 205,400 VA
1st. 3000 VA @ 100 % = 3,000 VA
next 117,000 VA @ 35% = 40,950 VA
remainder [205.4 kVA - 120 kVA] = 85,400 VA @ 25% = 21,350 VA
Total demand = 65,300 VA
All of the following copper conductors are to be installed in an electrical metallic tubing (EMT) ten (10) feet long:
- 24 - size 10 AWG THHW
- 10 - size 10 AWG THHN
- 14 - size 12 AWG THHN
Determine the MINIMUM trade size EMT required.
2 in.
Size 10 AWG THHW = .0243 sq. in. x 24 = 0.5832 sq. in.
Size 10 AWG THHN = .0211 sq. in. x 10 = 0.2110 sq. in.
Size 12 AWG THHN = .0133 sq. in. x 14 = 0.1865 sq. in.
Total = 0.9807 sq. in.
2 in. EMT with a 40% allowable fill of 1.342 sq. in. should be selected from Table 4 of Chapter 9.
Given: A 40 unit apartment complex with a 120/240-volt, single-phase electrical system is to add a 6,000 watt, 240 volt, single-phase clothes dryer in each unit. How many amperes will the clothes dryers add to the ungrounded (line) service-entrance conductors when applying the general method of calculation?
265 amperes
Demand = 35% minus .5% for each dryer exceeding 23
40 dryers – 23 = 17 (exceeding 23) x .5% = 8.5%
35% - 8.5% = 26.5% demand
40 dryers x 6 kW = 240 kW x 26.5% (demand) = 63.6 kW
63.6 kW x 1000 = 63,600 watts
I = P ÷ E I = 63,600 watts ÷ 240 volts = 265 amperes
Fill in the blank:
When sizing time-delay fuses for a branch circuit serving a hermetic refrigerant motor compressor, the device shall not exceed ________ of the rated load current marked on the nameplate of the equipment.
225 percent
