Load calculations are where a lot of journeyman candidates lose time and points. You need to know the VA per square foot, the demand factors, and how branch circuits and feeders get sized.
Every question here is based on the 2023 NEC. Some states are on a different edition, so check which one your exam uses.
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Question 1 of 15
A subpanel was installed with its bonding screw left in. With only normal 120-volt loads running and no fault present, a clamp meter on the feeder's equipment grounding conductor reads 6 amps. What is the BEST explanation?
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Answer: A. The downstream neutral bond lets normal neutral current split onto the EGC and other metal paths
With the neutral bonded to the enclosure in the subpanel, the neutral and the EGC are connected at both ends. Normal neutral current then divides between them as parallel paths. That is objectionable current, which 250.6 addresses and which the load-side bonding rules in 250.24(B) and 250.142(B) prevent. Removing the bonding screw puts the neutral current back on the neutral only.
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Question 2 of 15
A 1,800 VA load is supplied by a 120V branch circuit. The load current is approximately:
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Answer: A. 15 A
I = 1,800 ÷ 120 = 15 A.
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Question 3 of 15
A dwelling has four small-appliance branch circuits installed that qualify under 220.52(A). Using the standard method, what load is added for these circuits before demand factors are applied?
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Answer: A. 6,000 VA
NEC 220.52(A) assigns 1,500 VA to each 2-wire small-appliance branch circuit. 4 × 1,500 = 6,000 VA. This load may be included with the general lighting load, where demand factors are applied afterward.
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Question 4 of 15
A detached garage is supplied from the house by a feeder that includes an equipment grounding conductor. The garage has its own grounding electrode. How are the neutral and grounding connections made at the garage panel?
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Answer: A. The neutral stays isolated; the EGC and grounding electrode conductor connect to a ground bar bonded to the enclosure
Under 250.32(B)(1), where a separate building is supplied by a feeder with an equipment grounding conductor, the grounded conductor must not be connected to the EGC or to the grounding electrode. The EGC bonds the enclosure and connects to the building's grounding electrode system, which 250.32(A) generally requires. Bonding the neutral at the garage would put normal neutral current on the EGC and metal parts.
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Question 5 of 15
A 3,000 VA load is supplied at 120V. What is the approximate load current?
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Answer: A. 25 A
I = 3,000 ÷ 120 = 25 A.
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Question 6 of 15
A dwelling has four fastened-in-place appliances on the same service: a 4,500 W water heater, a 1,200 W dishwasher, a 900 W disposer, and a 1,000 W trash compactor. Using the 75% demand factor of 220.53, what is the demand load?
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Answer: C. 5,700 VA
NEC 220.53 permits a 75% demand factor for four or more fastened-in-place appliances (each rated ¼ hp or 500 W or more) on the same feeder or service in a dwelling. Ranges and other fastened-in-place cooking equipment, dryers, space heating, A/C, and EVSE are excluded. Total = 4,500 + 1,200 + 900 + 1,000 = 7,600 VA; 7,600 × 0.75 = 5,700 VA.
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Question 7 of 15
A panelboard in the same building is supplied by a feeder from the service equipment, with wire-type equipment grounding conductors. Which statement is TRUE in a code-compliant installation?
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Answer: A. The grounded (neutral) conductors terminate on an isolated neutral bar, and equipment grounding conductors terminate on a bar bonded to the enclosure
For a service-supplied system, the neutral-to-ground bond is made only at the service equipment. On the load side, the grounded conductor must not be connected to equipment grounding conductors or the enclosure (250.24(B), 250.142(B)). So in the downstream panel the neutral bar stays isolated, and the EGCs land on a ground bar bonded to the enclosure. This gives an effective fault-current path without putting normal neutral current on metal parts (250.6).
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Question 8 of 15
Which branch-circuit rule is MOST directly associated with providing required small-appliance circuits in dwellings?
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Answer: A. 210.11(C)(1)
NEC 210.11(C)(1) addresses required small-appliance branch circuits in dwelling units.
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Question 9 of 15
A dwelling clothes dryer has a nameplate rating of 4,000 W. What load is used for the dryer in a standard-method dwelling calculation?
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Answer: D. 5,000 VA
NEC 220.54 requires the dryer load to be calculated at 5,000 watts (volt-amperes) or the nameplate rating, whichever is larger. 5,000 VA is larger than the 4,000 W nameplate.
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Question 10 of 15
A feeder conductor is undersized for the calculated load. Which action is MOST code-aligned?
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Answer: A. Increase the feeder conductor size (or revise installation conditions) so ampacity meets the load
If the feeder is undersized, the code-aligned fix is to increase conductor size or change conditions so the corrected/adjusted ampacity meets the required load.
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Question 11 of 15
A permanently connected appliance is rated not over 300 volt-amperes. What may serve as its disconnecting means?
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Answer: B. The branch-circuit overcurrent device
NEC 422.31(A) permits the branch-circuit overcurrent device to serve as the disconnecting means for permanently connected appliances rated not over 300 volt-amperes or 1/8 horsepower.
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Question 12 of 15
Where would you MOST likely look for the optional method for calculating feeder/service loads for a dwelling unit?
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Answer: A. 220.82
NEC 220.82 covers the optional method for dwelling unit feeder and service load calculations.
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Question 13 of 15
A feeder supplies a subpanel where none of the connected equipment requires a neutral (only 240-volt water heater and air-conditioner circuits). Which statement is MOST accurate?
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Answer: A. A neutral isn't required for these loads, but an equipment grounding path is still required
A neutral is needed only where connected equipment requires one. An equipment grounding path is still required to bond the enclosures and clear faults. It can be a wire-type EGC or a qualifying metal raceway under 250.118.
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Question 14 of 15
A 20-amp branch circuit supplies only a continuous load. Assume the 100%-rated assembly exception doesn't apply. What is the MAXIMUM continuous load permitted?
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Answer: A. 16 A
NEC 210.20(A) requires the overcurrent device to be rated at least 125% of the continuous load, so the continuous load on a 20A circuit is limited to 20A ÷ 1.25 = 16A (80% of the rating).
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Question 15 of 15
Using the optional multifamily calculation (Table 220.84), what demand factor applies to a building with four dwelling units?
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Answer: A. 45%
Table 220.84 assigns a 45% demand factor to buildings with 3 to 5 dwelling units. It's applied to the dwelling units' connected load calculated under 220.84; house loads are calculated separately under Part III and added.
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Write out every step. Most load calc mistakes come from skipping a demand factor or using the wrong table.
If the article numbers threw you off, remember the 2023 NEC moved some load calc rules around compared to 2020.
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