Written against the 2026 NEC and checked section by section, September 2026
HVAC Circuits Practice Questions
A sealed compressor has no horsepower on its plate, so Article 440 works from the currents the manufacturer measured and modifies Article 430 rather than replacing it. These 25 items work the rated-load and branch-circuit selection currents, the conductor and device percentages, the marked minimum circuit ampacity and maximum device rating, the disconnect rules, and the outdoor ground-fault subsection at 210.8(F) with all three of its exceptions.
Pick an answer and the explanation opens with the section it comes from. These are original questions written for this site, not questions from the exam. Have your own code book open: the Texas exam is open book, and looking the section up is the skill being tested.
Read the hvac circuits study page first if the topic is new to you.
1. Why does a condensing unit send you to Article 440 instead of the general motor article?
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D. The compressor and its motor are sealed in one housing with no horsepower rating, so the sizing works from a current on the nameplate
The ordinary method starts by looking a horsepower up in a full-load current table, and a hermetic compressor has none to look up. So the article works from what the manufacturer measured. It modifies the motor article rather than replacing it, which is why an item about a rooftop unit can send you to two articles.
NEC 2026 440.1, 440.6
2. A nameplate prints both a rated-load current and a branch-circuit selection current. Which one is used to size the conductors and the protective device?
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A. The branch-circuit selection current, because it is never the smaller of the two
Where a branch-circuit selection current is marked, the code uses it in place of the rated-load current for the disconnect, the conductors, the controller and the protective device. That is why the sizing rules keep saying whichever is greater. A nameplate that prints both numbers is handing you a decision and testing whether you noticed.
NEC 2026 440.6
3. A single motor-compressor has a rated-load current of 32 amperes and no branch-circuit selection current marked. Copper conductors land on 75 degree C terminations, and no correction or adjustment applies. What is the smallest conductor?
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B. 8 AWG
Conductors for a single motor-compressor carry not less than 125 percent of the governing current, so 32 times 1.25 is 40 amperes. In the 75 degree column, 10 AWG copper carries 35 amperes and 8 AWG carries 50, so 8 AWG is the first size that reaches 40. Reading the 90 degree column instead is how 10 AWG becomes tempting.
NEC 2026 440.32, Table 310.16
4. The same compressor has a rated-load current of 32 amperes and no maximum device rating on the nameplate. What is the largest inverse time circuit breaker the branch circuit rules permit?
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C. 60 amperes
The base permission is a device not exceeding 175 percent of the governing current, and 32 times 1.75 is 56 amperes. That is not a standard rating, and an exception permits going up to the next standard rating, which is 60. The 50 ampere answer comes from rounding down instead of using the exception.
NEC 2026 440.22, 240.6(A)
5. That 32 ampere compressor will not start on the device the first calculation gives. How far up does the code let the rating go?
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A. 70 amperes, since the ceiling is 225 percent of the governing current
A second exception opens the ceiling where the device sized under the first rule will not carry the starting current, and it stops at 225 percent. Here 32 times 2.25 is 72 amperes, so the largest standard rating that stays at or below it is 70. This ceiling is a permission and not a target.
NEC 2026 440.22, 240.6(A)
6. A separate overload relay responsive to motor-compressor current protects that same 32 ampere compressor. What is the highest current at which it may be selected to trip?
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B. 44.8 amperes
The overload rule is a separate percentage from a separate starting number, and it is 140 percent of the rated-load current. That gives 32 times 1.4, or 44.8 amperes. The 40 ampere figure is the conductor calculation and the 56 is the short-circuit calculation, and both are offered because candidates reuse the wrong percentage.
NEC 2026 440.52
7. What is the minimum ampere rating of the disconnecting means for a motor-compressor with a rated-load current of 32 amperes?
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C. 36.8 amperes
The disconnect is rated at least 115 percent of the rated-load current or the branch-circuit selection current, whichever is greater, so 32 times 1.15 gives 36.8 amperes. A separate rule handles a listed unfused motor circuit switch with an adequate horsepower rating, which is permitted to fall below that figure.
NEC 2026 440.12
8. One circuit supplies a motor-compressor at 24 amperes rated-load current, a condenser fan motor at 3.5 amperes and an indoor blower at 2.5 amperes. What conductor ampacity does the article call for?
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D. 36 amperes
The rule adds the compressor currents, adds the full-load currents of the other motors, then adds 25 percent of the largest single motor in the group. That is 24 plus 3.5 plus 2.5, which is 30, plus 25 percent of 24, which is 6, for 36 amperes. Multiplying the whole 30 by 1.25 gives 37.5 and is the error the option list is built around.
NEC 2026 440.33
9. A packaged rooftop unit is marked with a minimum circuit ampacity. What does that number do?
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B. It sets the floor for the conductor ampacity, so the conductor is selected at or above it
The manufacturer has already combined the compressor, the fans and any electric heat in the cabinet and applied the multipliers, and printed the result. Your job is to select a conductor that carries at least that after your own ambient and bundling corrections and after the termination limit. The marking does not do the termination check for you.
NEC 2026 440.35, 440.4
10. The same nameplate marks a maximum rating for the branch-circuit short-circuit and ground-fault protective device. How is the device selected?
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C. The largest standard device at or below the marked value
This is where the habit from ordinary motor problems costs the item. On a motor branch circuit you calculate and round up, and here a printed maximum is a ceiling that neither percentage gets you past. Rounding up past the marking produces an answer that will be sitting in the option list.
NEC 2026 440.22, 440.4
Ten down. If you want these timed and scored by content area, the practice exam runs thirty questions free, and the full bank of 178 plus the calculation ladder is $79 once.
11. A unit is marked with both a minimum circuit ampacity and a maximum overcurrent device rating. Which way does each number round?
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D. The conductor is selected at or above the ampacity, and the device at or below the maximum
One number is a floor and the other is a ceiling, and getting them the wrong way round is the most common miss on this equipment. A device too large will not protect the wiring inside the cabinet, and a conductor too small will not carry what the equipment draws. Say which is which before you touch a table.
NEC 2026 440.35, 440.22
12. A small motor-compressor has no locked-rotor current marked on its nameplate. What does the article tell you to assume?
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A. Six times the rated-load current
The article supplies a substitute figure so the disconnect and controller work can go on without the marking, and it reaches small motors not covered by the full-load current tables as well. Locked-rotor current is what a horsepower rated switch is checked against, so a missing marking cannot be allowed to stop the calculation.
NEC 2026 440.12
13. A disconnecting means is being located for a packaged air-conditioning unit. Which location does the code rule out?
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C. On a panel that has to be removed to reach the equipment
The disconnect is allowed to sit on or within the equipment, which is how most packaged units come. What the section refuses is a location on an access panel, and it separately refuses any location that covers the nameplate. Hiding the nameplate would hide the two marked numbers the sizing depends on.
NEC 2026 440.14
14. A disconnect switch is mounted on the side of a rooftop unit. Which general requirement still applies to it?
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D. The working space requirements at 110.26(A)
The location section points at the general working space rule by number, so the depth, width and height figures come along with the disconnect wherever it lands. That is a real design constraint on a crowded roof curb and a straightforward item to write.
NEC 2026 440.14, 110.26(A)
15. An outdoor disconnecting means serves one condensing unit of a split system in an apartment building. What does the 2026 edition require at that disconnect?
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A. A marking giving the location of the indoor units it supplies
This is a new section aimed at a bank of outdoor units against one wall with no way to tell which apartment each one serves. It applies in other than one- and two-family dwellings, so the single family house next door is outside it. New sections get written into items early.
NEC 2026 440.15
16. A servicing receptacle outlet is required near heating, air-conditioning and refrigeration equipment. What does the section state?
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B. A 125 volt, single-phase, 15 or 20 ampere receptacle outlet at an accessible location within 25 feet of the equipment
The rating, the location and the distance are all in that one section, so it is a clean lookup once you know it exists. A separate subsection sets a second requirement for other than dwelling units, near indoor switchboards, switchgear, panelboards, motor control centers and service equipment.
NEC 2026 210.63
17. Which of these is not permitted for that servicing receptacle outlet?
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D. Connecting it on the load side of the equipment's branch-circuit disconnecting means
The point of the outlet is that a technician has power while working on the equipment, and putting it downstream of the equipment disconnect takes that away at exactly the wrong moment. Same level and within the stated distance are the two location conditions the section does state.
NEC 2026 210.63
18. Which equipment is specifically excused from the servicing receptacle requirement?
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B. An evaporative cooler at a one- or two-family dwelling
One narrow exception names evaporative coolers and limits itself to one- and two-family dwellings. Everything else in the scope of that section keeps the outlet. Exceptions this small are common exam material because they are easy to write four plausible options around.
NEC 2026 210.63
19. The outdoor outlet subsection for dwellings reaches circuits within what limits?
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A. Single-phase, 150 volts or less to ground, 60 amperes or less
Both numbers matter, and the ampere ceiling went up in this edition, so a study sheet written against the previous book gives the wrong figure. The subsection also names garages with floors at or below grade, accessory buildings and boathouses among the outdoor outlets it covers.
NEC 2026 210.8(F)
20. A listed Class C special purpose ground-fault device protects listed HVAC equipment at a dwelling. What does the code require alongside it?
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C. A warning marking on the disconnect serving the equipment saying the protection is provided
The third exception in that subsection permits the Class C route and asks for the marking so that whoever opens the disconnect knows what kind of protection is in the circuit. A Class C device is not the Class A device from a bathroom receptacle, and it lets more leakage current through before it opens.
NEC 2026 210.8(F)
21. An older outdoor unit at a dwelling is replaced with a new one, on an existing circuit with no ground-fault protection. What does the subsection say?
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B. The outlet is provided with ground-fault protection when the equipment is replaced
A sentence in the middle of the subsection reaches replacements, which is where a lot of this work actually happens. Reading only the list of covered locations and stopping there misses it. The exceptions still apply on their own terms once the replacement rule has brought the outlet into scope.
NEC 2026 210.8(F)
22. Which outlets does the first exception to that outdoor subsection release?
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D. Lighting outlets, other than those the code covers in a different subsection of the same section
The lighting exception is narrow and it carries a pointer to another subsection that keeps certain lighting outlets covered. Read all three exceptions while the book is open rather than only the one being argued about, because the third one answers a question the second cannot reach.
NEC 2026 210.8(F)
23. Which of these appears on the nameplate of multimotor and combination-load equipment?
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C. The minimum supply circuit conductor ampacity and the maximum rating of the branch-circuit short-circuit and ground-fault protective device
The marking rule lists the manufacturer name, the voltage, the frequency, the number of phases, the ampacity floor, the device ceiling and the short-circuit current rating of the controllers. It gives you a current, not a wire size, because the size still depends on your material, ambient and terminations.
NEC 2026 440.4
24. A room air conditioner is cord connected. What may serve as its disconnecting means?
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A. The attachment plug and receptacle, or a separable connector
The article permits the plug and receptacle to serve as the disconnect for cord-connected equipment such as room air conditioners, household refrigerators and freezers, drinking water coolers and beverage dispensers. Where that is the arrangement, the location has to be accessible but is not required to be readily accessible.
NEC 2026 440.13, 440.14
25. What does the 2026 edition require of factory-assembled electric motor-driven air-conditioning and refrigerating equipment?
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D. That it be listed
A listing requirements section sits near the front of the article in the 2026 template, and it also covers electric heaters field installed inside the enclosure of listed equipment, which have to be identified as a listed field installable accessory. Sections in the .2 position of an article are worth a glance for exactly this reason.
NEC 2026 440.2
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