Delmar's Standard Textbook of Electricity (MindTap Course List)
6th Edition
ISBN: 9781285852706
Author: Stephen L. Herman
Publisher: Cengage Learning
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Chapter 11, Problem 7PP
A bank of electric heaters has a power rating of 25 kW. The heaters are connected to 480 volts. The heaters will operate for more than three hours at a time. The conductors supplying the heaters are to be aluminum with type THWN-2 insulation. The heaters are located in an area with an ambient temperature of
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Chapter 11 Solutions
Delmar's Standard Textbook of Electricity (MindTap Course List)
Ch. 11 - What is the maximum temperature rating of Type...Ch. 11 - 2. Name two types of conductor insulation designed...Ch. 11 - A 10 AWG copper conductor with Type THW insulation...Ch. 11 - 4. Six 1/0 aluminum conductors are to be run in a...Ch. 11 - Name five conditions that must be met for running...Ch. 11 - What is the largest solid (nonstranded) conductor...Ch. 11 - Can Type TW cable be used in an area that has an...Ch. 11 - How is the grounded conductor in a flat...Ch. 11 - What three colors are ungrounded conductors not...Ch. 11 - Twenty-five 12 AWG copper conductors are run in...
Ch. 11 - A single-hase load is located 2800 ft from its...Ch. 11 - It is decided to use parallel 0000 conductors to...Ch. 11 - A three-phase motor operates on 480 V and is...Ch. 11 - You have been hired by a company to connect an...Ch. 11 - 2. You are a journeyman electrician in an...Ch. 11 - You are an electrician working in an industrial...Ch. 11 - Using the above example, determine the wire size...Ch. 11 - 1. A 2 AWG copper conductor is 450 ft long. What...Ch. 11 - 2. An 8 AWG conductor is 500 ft long and has a...Ch. 11 - 3. Three 500-kcmil copper conductors with Type RHH...Ch. 11 - 4. Eight 10 AWG aluminum conductors with Type THWN...Ch. 11 - 5. A three-phase motor is connected to 480 V and...Ch. 11 - 6. A 50-hp DC motor is connected to 250 volts. The...Ch. 11 - 7. A bank of electric heaters has a power rating...Ch. 11 - A 15-hp squirrel-cage induction motor is connected...Ch. 11 - Determine the resistance of a 16 AWG copper...Ch. 11 - Determine the ohms-per-mil-foot of an aluminum...
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- A certain type of control connects electric heating units to a 120-volt supply or a 240-volt supply, depending on the amount of the temperature drop in a room. These controls are supplied from a 120/240-volt, 3-wire, single-phase source. Assuming that this type of device controls a 240-volt, 2000-watt heating unit, what is the wattage produced when the control supplies 120 volts to the heating unit? Show all calculations. ______________________________________________________________________ ______________________________________________________________________arrow_forwardAn electric dryer is rated at 7.5 kW and 120/240 volts, 3-wire, single-phase. The terminals on the dryer and panelboard are marked 75C. a. What is the wattage rating? ___________ b. What is the current rating? ___________ c. What minimum size type THHN copper conductors are required? ___________ d. If EMT is used, what minimum size is required? ___________arrow_forward8. What is the maximum load to be connected to a single receptacle rated at 20A?arrow_forward
- DETERMINE THE PROPER SIZE CONDUCTORS for a 500 watt load that is located 100 ft from a 250 volt panelboard the permissable line drop is 2 volts and k=12.6arrow_forwardEighty 16 AWG copper conductors with type THWN-2 insulation are to be run in a conduit. The conduit used in an area that has an ambient temperature of 120 F. What is the maximum ampacity of these conductors?arrow_forwardHow many lighting branch circuits are provided in this dwelling? __________ a. What is the minimum load allowance for small-appliance circuits for dwellings? See NEC 220.52(A). __________ b. An individual 15-ampere branch circuit is run to the receptacle outlet behind the refrigerator instead of connecting it to one of the two 20-ampere small-appliance branch circuits that are required in kitchens. For this separate circuit, an additional 1500 volt-amperes (shall) (does not have to) be added to the load calculations for dwellings. (Circle the correct answer.)arrow_forward
- Show the connections for a ceiling outlet that is to be controlled from any one of three switch locations. The 120-volt feed is at the light. Use colored pens or pencils. Assume the installation is in cable.arrow_forwardA central air-conditioning unit is rated at 4,100 watts. The unit uses 230 volts.How many amperes of current does the electrical cable for this unit carrywhen current is flowing?arrow_forwardThe branch circuit supplying a fixed electric space heater must be sized to at least ___________ percent of the heaters rating according to NEC ________________.arrow_forward
- Refer to the specifications in the back of this text following Chapter 33. a. What electrical codes must be conformed to? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ b. What is the wiring method to be used in the workshop? ________________________________________________________________________ c. What size conductors are to be used for the lighting branch circuits? ______________________ AWG the small-appliance branch circuits? ______________________ AWG d. What section of the specifications tells us the size of the service entrance to be installed for this residence?arrow_forwardIs it permissible to use standard 60C insulated conductors to connect all counter-mounted cooking units? ___________________________________________________ Why? ________________________________________________________________arrow_forwardDetermine the proper size of copper wire conductor necessary to apply a 750 W electric motor that is located 100 feet from the panel board. The voltage at the panelboard is 120 volts. The permissible line drop is 1.2 volts. (for your final answer: no decimal places and unit to have one common answer)arrow_forward
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