Journeyman/Master Electrician License Exam Electrical Load Calculations Syllabus

Electrical Load Calculations syllabus — full chapter and topic list

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

1. 1

   Dwelling Unit Calculations

   4 topics

   • Standard Method (Article 220 Part III)
     • General lighting load at 3 VA per square foot
     • Small-appliance and laundry circuit loads
     • Lighting/receptacle demand factors (Table 220.42)
   • Appliance and Equipment Loads
     • Range and cooking equipment demand (Table 220.55)
     • Dryer load demand (Table 220.54)
     • Fixed appliance 75% demand factor (four or more)
   • Heating, Air Conditioning, and Largest-Motor Loads
     • Omitting the smaller of heat vs. AC
     • Adding 25% of the largest motor
   • Optional Method (220.82)
     • First 10 kVA at 100%, remainder at 40%
     • Comparing standard vs. optional results
2. 2

   Commercial and Multifamily Calculations

   3 topics

   • Commercial Occupancy Loads
     • Show window, sign, and outlet loads
     • Receptacle load demand (Table 220.44)
   • Multifamily Dwelling Calculations
     • Standard vs. optional multifamily methods (220.84)
     • House loads and common areas
   • Service and Feeder Sizing
     • Determining minimum service ampacity
     • Neutral/grounded conductor load (220.61)
3. 3

   Conductor Sizing and Voltage Drop

   3 topics

   • Selecting Conductors for Calculated Loads
     • Coordinating ampacity with overcurrent protection
     • Parallel conductor rules (310.10(G))
   • Voltage Drop Calculations
     • Single-phase and three-phase VD formulas (K-method)
     • Recommended 3% branch / 5% total limits
   • Adjusting Conductor Size for Conditions of Use
     • Combining ambient and fill adjustment factors
     • Selecting the controlling (lowest) ampacity

Electrical Load Calculations flashcards for Journeyman/Master Electrician License Exam

25 of 52 cards from the Electrical Load Calculations deck — real questions with worked answers.

1. Under the NEC Standard Method (Article 220, Part III), what is the minimum general lighting load value used for a dwelling unit, and on what is it based?

   $3 \text{ VA/ft}^{2}$ ($33 \text{ VA/m}^{2}$), applied to the outside dimensions of the dwelling. This general lighting load already includes the general-use receptacle outlets in a dwelling.

2. In the Standard Method, how do you determine the floor area used for the general lighting load calculation of a dwelling?

   Use the outside dimensions of the dwelling. Do NOT include open porches, garages, or unused/unfinished spaces unless they are adaptable for future use.

3. What are the two required small-appliance branch circuits' load and the laundry branch circuit load that must be added in a dwelling Standard Method calculation?

   Each small-appliance circuit (minimum two) is figured at $1500 \text{ VA}$ each, and the laundry circuit is figured at $1500 \text{ VA}$. So two small-appliance circuits plus one laundry circuit add $4500 \text{ VA}$.

4. What are the NEC general lighting demand factors (Table 220.42) for a dwelling unit?

   First $3000 \text{ VA}$ at 100%, the portion from $3001$ to $120{,}000 \text{ VA}$ at 35%, and any remainder over $120{,}000 \text{ VA}$ at 25%.

5. In the Standard Method, the demand factors of Table 220.42 are applied to the sum of which loads in a dwelling?

   The sum of the general lighting load ($3 \text{ VA/ft}^{2}$), the two small-appliance circuits, and the laundry circuit. These are totaled first, then the 100%/35%/25% demand factors are applied.

6. What is the maximum demand factor that may be applied to four or more dwelling-unit fixed appliances (other than ranges, dryers, space heating, A/C) per NEC 220.53?

   A demand factor of 75% may be applied to the nameplate load of four or more fastened-in-place appliances served by the same feeder/service in a one-family dwelling.

7. How is the load for a household electric clothes dryer determined under NEC 220.54?

   Use the nameplate rating or $5000 \text{ VA}$, whichever is larger. For one dryer the demand is 100%; demand factors from Table 220.54 apply when there are multiple dryers.

8. Under NEC 220.55, how is the demand load for a single household electric range rated not over 12 kW determined using Table 220.55 Column C?

   Column C gives a demand of $8 \text{ kW}$ for one range rated not over $12 \text{ kW}$.

9. Per NEC 220.55 Note 1, how do you adjust the Column C range demand when a range is rated over 12 kW (up to 27 kW)?

   Increase the Column C value by 5% for each kW (or major fraction) by which the rating exceeds 12 kW. For example, a 16 kW range: $8 \text{ kW} \times (1 + 4 \times 0.05) = 8 \times 1.20 = 9.6 \text{ kW}$.

10. When ranges of unequal ratings are used together, how is the average rating found for applying Table 220.55 Note 2?

    Add all the individual kW ratings and divide by the number of ranges. Any range under 12 kW is counted as 12 kW for computing the average.

11. What is the rule for sizing a branch circuit for the largest motor when including it in a service or feeder calculation (NEC 220.50 / 430.24)?

    Add 25% of the full-load current (or VA) of the largest motor to the sum of the other motor loads and the rest of the calculated load.

12. In a dwelling Standard Method calculation, how are fixed electric space heating and air-conditioning loads treated (NEC 220.60)?

    They are noncoincident loads — only the larger of the two needs to be included in the calculation, since heating and cooling do not operate simultaneously. The smaller load may be omitted.

13. Per NEC 220.60, when two noncoincident loads are unlikely to operate at the same time, which one is used in the service/feeder calculation?

    Only the larger of the two noncoincident loads is included; the smaller is omitted.

14. What demand factor applies to fixed electric space-heating loads for feeders/services under NEC 220.51?

    Fixed electric space heating is calculated at 100% of the total connected load.

15. When an air conditioner and the largest motor must both be considered, and the A/C compressor IS the largest motor, how do you apply the 25% factor?

    Apply the 25% largest-motor addition to the hermetic refrigerant compressor's rated-load current if that compressor is the largest motor in the system, per NEC 430.24 / 220.50.

16. What is the NEC Optional Method calculation for a one-family dwelling found in (cite the section)?

    NEC 220.82 — the Optional Calculation for a Dwelling Unit, permitted when the service or feeder is rated at least 100 A, 3-wire.

17. Under the Optional Method (220.82), how are the general loads computed before applying demand factors?

    Sum at 100% (nameplate VA): $3 \text{ VA/ft}^{2}$ general lighting, $1500 \text{ VA}$ per small-appliance and laundry circuit, and the nameplate rating of all fastened-in-place/permanently connected appliances (ranges, dryers, water heaters, etc.).

18. What demand factors does NEC 220.82(B) apply to the total general load in the Optional Method?

    First $10 \text{ kVA}$ of the general load at 100%, and the remainder over $10 \text{ kVA}$ at 40%.

19. List the heating/AC selection options in NEC 220.82(C) — which value is used as the largest?

    Use the largest of: (1) 100% of the A/C and cooling equipment; (2) 100% of heat pump compressors (without supplemental heat); (3) 100% of heat pumps with supplemental heat; (4) 65% of central electric space heating; (5) 65% of <4 separately controlled electric space heating units; (6) 40% of 4 or more separately controlled space heating units.

20. In the Optional Method 220.82, after computing the general load demand and the heating/cooling load, how do you get the total calculated load?

    Add the demand result from 220.82(B) (general loads) to the largest heating/cooling selection from 220.82(C). Then convert VA to amperes by dividing by the system voltage.

21. Compare the Standard Method and Optional Method (220.82) — which typically yields a smaller calculated service size and why?

    The Optional Method usually yields a smaller (or equal) result because its demand factors (100% of first 10 kVA, then 40% of remainder, plus reduced heating percentages) are more generous, reflecting diversity. The Standard Method is more conservative.

22. Convert a calculated dwelling load of $24{,}000 \text{ VA}$ on a 240 V, single-phase service to amperes.

    $I = \dfrac{24{,}000 \text{ VA}}{240 \text{ V}} = 100 \text{ A}$.

23. What is the general lighting load unit value for an office building under NEC Table 220.12 (general illumination, where used)?

    Office buildings are figured at approximately $1.3 \text{ VA/ft}^{2}$ (general lighting). Note: receptacle loads are computed separately in commercial occupancies, unlike dwellings.

24. In commercial occupancies, how are general-use receptacle outlets calculated under NEC 220.14(I)?

    Each single or multiple receptacle on one strap is figured at $180 \text{ VA}$. (Multioutlet assemblies are figured per 220.14(H).)

25. What demand factors may be applied to commercial/nondwelling receptacle loads exceeding 10 kVA per NEC 220.44 and Table 220.44?

    First $10 \text{ kVA}$ at 100% and the remainder over $10 \text{ kVA}$ at 50%.

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