Final Examination No. 2

Total Time: 6 Hours

Only the Code Book May Be Used
for the Open-Book Portion

I. Problems (Closed-Book) Test Time: 2 Hours

1. Define the following:

(a) Feeder

(b) Appliance

(c) Branch circuit

(d) Overload

(e) Vented power fuse

2. What is the minimum height of a 120/240-volt service drop over the following:

(a) Sidewalk

(b) Residential driveway

(c) Public streets

3. What is the color of the finish for the high-voltage conductor in a high-leg delta feeder?

4. What are the requirements for lighting outlets in a one-family dwelling?

5. Which receptacles must have GFCI protection in one-family dwellings?

6. Plug fuses may be used to protect 120/240-volt, single-phase circuits. True or false?

7. An aluminum grounding conductor must not be used outside within ________ inches of the earth.

8. Metal water pipes used in the grounding electrode system must have a length of ________ feet or more.

9. Select the size aluminum conductors allowed in a single-phase residential service rated at (a) 100 amperes (b) 125 amperes (c) 150 amperes (d) 200 amperes.

10. Conductors of a 120-volt circuit may occupy the same raceway as a 4160-volt circuit if the low-voltage conductors are insulated for 5000 volts. True or false?

11. If six 300-kcmil THW conductors are enclosed in conduit, what is the ampacity as a percentage of the rated ampacity?

12. Rigid metal conduit of size 1 inch must be supported at least every ________ feet if a straight run with threaded couplings is used.

13. In a wireway, the cross-sectional area of conductors must not exceed ________ % of the area of the wireway and the area of splices must not exceed ________ %.

14. A device box with a volume of 12 cubic inches may hold up to ________ No. 14 conductors.

15. Busways may extend ________ feet from their supply if the current rating is at least ________ of the rating of the overcurrent device next back on the line.

16. Auxiliary gutters must not extend farther than ________ feet and contain more than ________ current-carrying conductors that are not derated.

17. Conductors for wiring lighting fixtures must not be smaller than ________.

18. A room air conditioner must be rated less than ________ amperes and ________ volts, single-phase. A flexible cord supplying a 208-volt unit must not exceed ________ feet in length.

19. The ampacity of conductors supplying a capacitor must be at least ________ % of the rated current of the capacitor. What is the setting of the overcurrent device?

20. A location in which electrically conductive dusts are present is a Class I, Division 1 area. True or false?

21. An area in which rayon is manufactured is classified as:

(a) Class II, Division 2

(b) Class III, Division 1

(c) Class III, Division 2

(d) Class I, Division 1

22. Type MI cable may be used in all hazardous locations. True or false?

23. At a gasoline pump the first fitting used as the conduit supplying the pump leaves the ground must be a ________. What is the next fitting?

24. Near a gasoline dispenser the area up to ________ inches from the base and extending ________ feet is a Class I, Division 2 location.

25. In the following circuit, determine the quantities listed:

(a) The reactance of the inductor

(b) The current the ammeter reads

(c) The voltage V1 across the resistor

(d) The voltage V2 across the coil

(e) The impedance of the circuit

26. What is the horsepower output of a 75-horsepower, three-phase motor with 85% efficiency and a .80 power factor if the voltage is 230 volts and the motor draws 192 amperes?

27. A motor with eight poles runs at 900 revolutions per minute is connected to a 60-hertz source. What will the speed be if the source frequency is 120 hertz?

28. A delta-wound, three-phase, 240/480-volt motor has nine terminals. Connect these terminals for (a) high-voltage operation and (b) low-voltage operation.

29. A motor controller has two remote start-stop stations and one jog station. Draw the one-line diagram.

II. Problems (Open-Book) Test Time: 4 Hours

1. A 100-unit apartment building is supplied by a 12,470Y/7200-volt service. Each apartment contains the following:

(a) 2000 square feet of living area

(b) 12-ampere, 120-volt dishwasher

(c) 6-ampere, 120-volt disposal

(d) 7.2-kilowatt counter-mounted cooking unit

(e) 7.2-kilowatt wall-mounted oven

(f) 5-kilowatt, 240-volt clothes dryer

(g) Washing machine

(h) 9.6-kilowatt, 240-volt electric heating

(i) 1½-horsepower, 240-volt air conditioner

The complex also contains a central 30-ampere, 480-volt, three-phase air conditioner for the recreation areas. The apartments are supplied by a single-phase, 7200/240/120-volt transformer and the motor is supplied by a separate 7200/480-volt, three-phase transformer.

Calculate the following:

(a) The feeder capacity for each apartment unit by using the standard method.

(b) The main-service conductor ampacity and the main fuse size by using the optional method for the apartment building load.

(c) The conductor ampacity and the fuse size for the motor circuit

2. A 140,000-square-foot department store is supplied by a 120/240 volt, high-leg delta circuit. The store contains the following:

(a) 40 duplex receptacles (continuous)

(b) 80 feet of show window (noncontinuous)

(c) 80-horsepower, 230-volt, three-phase motor

(d) Outside sign of 16 amperes

(e) Six hundred 100-watt fixtures for general illumination

Calculate the service capacity and transformer kilovolt-ampere rating.

3. Design the branch circuits and feeder supplying the following 460-volt, three-phase motors:

(a) 25-horsepower, squirrel-cage motor with service factor 1.15, code letter F

(b) Two 30-horsepower, wound-rotor motors

4. A 12,470-volt switchboard has exposed buses. The elevation of the buses must be at least ________ feet.

5. What is the impedance at 60 hertz of a 500-kcmil THW aluminum conductor in a steel raceway that is 800 feet long?

6. A 230-volt, three-phase squirrel-cage motor with a service factor of 1.2 has a power factor of .7 and draws 104 amperes. A capacitor is added to raise the power factor to 1.0. Find the following:

(a) The capacitor rating in VARS

(b) The rating of the required overload device for the motor if the capacitor is connected to the load side of the device

(c) The branch-circuit conductor ampacities for the motor circuit and the capacitor