Journeyman/Master Electrician License Exam Motors, HVAC, and Special Equipment Syllabus

Motors, HVAC, and Special Equipment syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Motors, HVAC, and Special Equipment in Journeyman/Master Electrician License Exam, not a summary of it.

1. 1

   Motor Circuits (Article 430)

   4 topics

   • Motor Conductor Sizing
     • Using FLC tables (Tables 430.247-430.250)
     • 125% of FLC for single-motor branch circuits
   • Motor Overload and Branch-Circuit Protection
     • Overload sizing (115%-125%)
     • Short-circuit/ground-fault device sizing (Table 430.52)
   • Feeders Supplying Multiple Motors
     • Sum of FLCs plus 125% of largest
     • Feeder protection for motor groups
   • Motor Controllers and Disconnects
     • Disconnecting means rating and location
     • Controller marking and sizing
2. 2

   Air Conditioning and Refrigeration (Article 440)

   3 topics

   • Hermetic Motor-Compressor Loads
     • Using rated-load current (RLA) vs. FLC
     • Branch-circuit selection current
   • Disconnecting Means and Overcurrent Protection
     • Disconnect sizing within sight of equipment
     • Minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP) nameplate use
   • Conductor Sizing for HVAC Equipment
     • Sizing to nameplate MCA
     • Combination loads with electric heat
3. 3

   Transformers and Capacitors (Articles 450 and 460)

   3 topics

   • Transformer Overcurrent Protection
     • Primary-only protection (Table 450.3(B))
     • Primary and secondary protection
   • Transformer Sizing and Conductor Connections
     • Primary and secondary conductor ampacity
     • Transformer vault and installation requirements
   • Capacitor Conductor and Protection Sizing
     • 135% of capacitor rated current

Motors, HVAC, and Special Equipment flashcards for Journeyman/Master Electrician License Exam

21 of 50 cards from the Motors, HVAC, and Special Equipment deck — real questions with worked answers.

1. When sizing the branch-circuit conductors for a single continuous-duty motor, what minimum percentage of the motor full-load current (FLC) must the conductor ampacity equal?

   At least 125% of the motor FLC (NEC 430.22): $I_{conductor} \geq 1.25 \times I_{FLC}$.

2. For sizing motor branch-circuit conductors, do you use the motor nameplate current or the NEC table FLC value?

   Use the FLC value from NEC Tables 430.247–430.250 (based on horsepower and voltage), NOT the nameplate current. Nameplate (actual FLA) is used only for overload sizing.

3. A 10 hp, 230 V, 3-phase motor has a table FLC of 28 A. What is the minimum branch-circuit conductor ampacity?

   $1.25 \times 28 = 35$ A minimum conductor ampacity.

4. Why does the NEC require table FLC values rather than nameplate values for conductor and branch-circuit protection sizing?

   Table values give a standardized, worst-case current so designs remain consistent regardless of the specific motor installed; nameplate current is reserved for sizing the overload (running) protection, which must match the actual motor.

5. For a continuous-duty motor, what is the conductor ampacity rule and which NEC section governs it?

   NEC 430.22: conductors supplying a single continuous-duty motor must have an ampacity of at least 125% of the motor's table FLC.

6. What percentage of nameplate FLA is used to size overload protection for a motor with a marked service factor of $1.15$ or greater?

   125% of the nameplate full-load amperes (NEC 430.32).

7. List the NEC 430.32 overload sizing percentages for the three motor categories.

   Service factor $\geq 1.15$: 125%; temperature rise $\leq 40^{\circ}\text{C}$: 125%; all other motors: 115% of nameplate FLA.

8. What does motor branch-circuit short-circuit and ground-fault protection (Table 430.52) protect against — and what does it NOT protect against?

   It protects against short circuits and ground faults. It does NOT protect against overloads (running overcurrent); overloads are handled separately by the overload device per 430.32.

9. Give the standard maximum Table 430.52 percentages of FLC for: nontime-delay fuse, dual-element (time-delay) fuse, instantaneous-trip breaker, and inverse-time breaker.

   Nontime-delay fuse 300%; dual-element (time-delay) fuse 175%; instantaneous-trip breaker 800%; inverse-time breaker 250%.

10. If the Table 430.52 standard values are not sufficient to allow the motor to start, what increased maximum percentages are permitted?

    Nontime-delay fuse up to 400%; dual-element (time-delay) fuse up to 225%; instantaneous-trip breaker up to 1300%; inverse-time breaker up to 400%.

11. If the calculated overload device does not allow the motor to start/run without tripping, what next-step maximum percentages does NEC 430.32(C) allow?

    Increase to: service factor $\geq 1.15 \to 140\%$; temperature rise $\leq 40^{\circ}\text{C} \to 140\%$; all others $\to 130\%$ of nameplate FLA.

12. What is the NEC 430.24 rule for sizing feeder conductors supplying several motors?

    Ampacity must be at least 125% of the highest-rated motor's FLC plus the sum of the FLCs of all other motors on the feeder.

13. State the formula for the minimum feeder conductor ampacity supplying multiple motors.

    $I_{feeder} = 1.25 \times I_{largest} + \sum I_{other}$, where $I_{largest}$ is the largest motor FLC and $\sum I_{other}$ is the sum of all other motor FLCs.

14. How is the maximum feeder overcurrent protective device sized for a group of motors (NEC 430.62)?

    It equals the largest branch-circuit OCPD rating of any one motor in the group plus the sum of the FLCs of all the other motors.

15. Three motors have FLCs of 28 A, 20 A, and 16 A; the largest motor's branch OCPD is 70 A. What is the maximum feeder OCPD, and what standard size is used?

    $70 + 20 + 16 = 106$ A maximum; since you may not exceed the calculated value, use the next standard size down: a 100 A device.

16. What is the minimum ampere rating of a motor disconnecting means relative to the motor's full-load current (NEC 430.110)?

    At least 115% of the motor full-load current: $I_{disc} \geq 1.15 \times I_{FLC}$.

17. What horsepower relationship must a motor controller have to the motor it serves?

    The controller must have a horsepower rating at or above the motor's rating. (Exception: a stationary motor of 2 hp or less, 300 V or less, may use a general-use switch rated at least twice the motor FLC.)

18. Per NEC 430.102, where must the motor controller disconnecting means be located relative to the controller?

    It must be located in sight from the controller location — visible and not more than 50 ft (15 m) away.

19. How does the NEC define the phrase “in sight from” (or “within sight”)?

    The equipment is visible from one another and is not more than 50 ft (15 m) apart.

20. What two capabilities/locations does the NEC require of the motor disconnecting means for the motor and driven machinery (430.102(B))?

    It must be capable of being locked in the open position and be located in sight from the motor location and the driven machinery (with limited exceptions where lockable provisions are allowed instead).

21. For a hermetic refrigerant motor-compressor, what current value replaces horsepower/FLC for sizing, and where is it found?

    The rated-load current (RLC), marked on the equipment nameplate. Because the motor and compressor are sealed together, shaft horsepower cannot be measured.

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