MASTER ELECTRICIAN PREP EXAM PART 3

1. If the source of supply is 125 feet away, the voltage drop for a 120 volt, 20 amp single phase circuit that supplies a 12 amp load and has circuit conductors with a combined resistance of 0.35 ohms would be which of the following:

2. If a 120 volt, 20 amp single phase feeder circuit supplies a 12 amp load and has circuit conductors with a combined resistance of 0.35 ohms, and the source of supply is 125 feet away, then the approved conductor size, based on the resulting voltage drop for this run, would be which of the following:

3. In an apartment building with a three-phase, four-wire, 120/208 electrical service with a singlephase, three-wire 120/208 feeder where two ungrounded and one neutral conductor runs to each dwelling unit, only the 120 volts loads are operating and the loads are balanced. If the current to each ungrounded conductor is 42 amperes, then the current of the neutral conductor to one dwelling unit is equal to which of the following:

4. Assume that a three-phase, 460 volt continuous load wound induction motor is rated at 40 horsepower, and the nameplate indicates the full load current is 45.5 amps and a secondary full load current of 82 amps. The motor is rated at a temperature rise of 40 degrees C. Based on the fact that the resistor bank is separate from the controller and is classified at “medium intermittent duty,” then the minimum current rating of the secondary conductors running between the motor and the controller must be no less than which of the following:

5. Building “A” is supplied with 120/240 volt single-phase power from building “B” on the same property. “B” is supplied from a three-wire with two ungrounded conductors and one neutral without any metallic water pipe or other metal equipment connections to the building or equipment ground fault protection installed. The neutral conductor must:

6. A copper THHN feeder conductor consists of 40 amperes of continuous load and 35 amperes of noncontinuous load, and supplies a load that does not contain any general use receptacles but has three current-carrying conductors in a raceway with terminations rated at 75( degrees C. This means that the minimum standard overcurrent device required for the feeder is which of the following:

7. If a feeder conductor contains type RHW 500 kcmil copper conductors protected by a 400 amp circuit breaker, and a tap is made to the feeder in order to supply a 100 amp main circuit breaker 22 feet from the tap location, then the minimum size copper type THWN conductor that is permitted between the tap and the panelboard is which of the following:

8. If a single family dwelling unit has 2680 square feet of living space and all of the 120 volt general illumination circuits are rated at 15 amperes, then the minimum number of circuits required is which of the following:

9. A single family dwelling with 2400 square feet of living area has a 120/240 volt three-wire electrical service and contains the following: a 3.5 kW 240 volt electric water heater, a 12 kW electric range, a 1.5 horsepower 240 volt central air conditioner, a 1/2 horsepower 120 volt garbage disposal,a 1/3 horsepower 120 volt furnace blower motor, a 1.2 kW 120 volt dishwasher, and a 5 kW clothes dryer. The total minimum load required for the general illumination, small appliances, and laundry without any demand factors would be which of the following:

10. A recreational vehicle located on one of 20 RV sites is connected to a 20 amp 125 volt receptacle, which must also be which of the following:

11. In an eight unit apartment building, each kitchen contains a 3.5 kW 240 volt electric range. The demand load for the electric service to the building must include an allowance for the minimum demand load of all of the ranges, which would be which of the following:

12. A retail store has 3000 square feet and 30 feet of show window. The service is a 120/240 volt singlephase 3-wire service, and there is an actual connectedl ighting load of 8500 VA. There are a total of 80 duplex receptacles. Given these facts, the total calculated load is which of the following:

13. The same retail store with 3000 square feet and 30 feet of show window, a 120/240 volt single phase 3- wire service, an actual connected lighting load of 8500 VA, and a total of 80 duplex receptacles would require a minimum standard feeder overcurrent protection size of which of the following:

14. A multi-family dwelling has 40 units, with 208Y/120 volt three-phase main service and two-phase legs and neutral running to two meter banks of 20 units each. One half of the units are equipped with 12 kW electric ranges rated in accordance with the requirements of NEC® Section [220.55], and the other units have gas ranges. The only laundry connections are in a laundry room in the basement,available to all of the tenants. Each apartment unit has 840 square feet. Given these conditions, the net calculated feeder neutral load is which of the following:

15. A multi-family dwelling has 20 units, with 120/240 volt single phase main service running to two meter banks of 20 units each. One half of the units are equipped with 12 kW electric ranges rated in accordance with the requirements of NEC® Section [220.55], and the other units have gas ranges. The only laundry connections are in a laundry room in the basement, available to all of the tenants. Each apartment unit has 840 square feet. Given these conditions, the minimum feeder size for units without electric ranges would be which of the following:

16. A project requires the installation of twelve 1.4 ampere, 120 volt, fluorescent lights fixtures on two 20 amp branch circuits, as well as three 120 volt, 5.6 ampere electric fans on individual circuits in a building with a 120/240 single phase three-wire electric service. The minimum neutral current allowed for these loads is which of the following:

17. A 200A feeder installed in Schedule 80 rigid nonmetallic conduit has three 3/0 THHN conductors, one 2 THHN conductor, and one 6 THHN conductor. What trade size raceway is required?

18. What trade size rigid metal nipple is required for three 4/0 THHN conductors, one 1/0 THHN conductor, and one 4 THHN conductor?

19. What is the ampacity of four current-carrying 1/0 THHN conductors in a raceway?

20. A raceway contains eight current-carrying conductors. What size conductor is required to feed a 21A noncontinuous load? The overcurrent protection device is rated 30A.

21. What is the ampacity of eight current-carrying 10 THHN conductors installed in an ambient temperature of 100°F?

22. The branch-circuit short-circuit protection device for a 10 hp, 230V, single-phase motor shall not exceed __               ‘ Note: Use an inverse-time breaker for protection.

23. The branch-circuit protection (circuit breaker) for a 125 hp, 240V, dc motor is __              .

24. The motor feeder conductor size for three 15 hp, three-phase, 208V motors; three 3 hp, single-phase, 208V motors; and three 1 hp, single-phase, 115V motors will be                           .

25. If an inverse-time breaker is used for the feeder short-circuit protection, what size protection is required for the following three-phase motors?

Motor 1 = 40 hp, 52 FLC Motor 2 = 20 hp, 27 FLC Motor 3 = 10 hp, 14 FLC Motor 4 = 5 hp, 7.6 FLC

26. What is the ac ohms-to-neutral resistance for 100 ft of 3 AWG copper conductor?

27. A 2-wire circuit supplies a 36A load that is located 100 ft from the panelboard. The load is wired with 1 THHN aluminum in PVC conduit. What is the total ac ohms-to-neutral resistance of the circuit conductors?

28. What size copper conductors in a steel raceway can be used to replace 110 AWG aluminum that supplies a 110A load? Note: We do not want to increase the circuit voltage drop.

29. A 24A, 240V, single-phase load is located 160 ft from the panelboard. The load is wired with 10 THHN. What is the approximate voltage drop of the branch-circuit conductors?

30. A 36 kVA, 208V, three-phase load is located 100 ft from the panelboard and is wired with 1 THHN aluminum. What is the approximate voltage drop of the circuit conductors?

31. A single-phase, 5 hp motor is located 110 ft from a panelboard. The nameplate indicates that the voltage is 115/230V and the FLA is 52/26A. What size conductor is required if the motor windings are connected in parallel and operate at 115V? Apply the NEC recommended voltage-drop limits.

32. Each unit of a 60-unit apartment building has a 4 kW dryer. Using the optional method, the calculated load that will be added to the service is                    kW.

33. A multifamily dwelling (40-unit) contains a 4.5 kW electric clothes dryer in each unit. What is the feeder and service calculated load for all of the dryers?

34. What is the general lighting and general-use receptacle load for a 30,000 sq ft bank?