Disconnecting Means Practice Questions

A. It is visible from the other, and not more than 50 feet away from it

The rule is a pair of conditions and both hold or neither does. An installation can pass one and fail the other, which is exactly what a stem describing a plan view with a wall in it is built to test. Being in the same room is neither condition, since a room can be long enough to break the distance and a partition can break the visibility inside one room.

NEC 2026 110.29

B. 110.29

This one moved. It reads as a rule in Article 110 rather than as a definition, and the service disconnect location rule points at that section by number. Section 430.102 is where the requirement lands on a motor circuit but it does not define the term. A candidate hunting the definitions for it will lose a minute before finding it.

NEC 2026 110.29, 230.70(A)

C. No, because the visibility half of the test fails

Distance passes and visibility fails, so the pair fails. Visibility is assessed as the installation stands rather than as anybody intended, which means a door that is kept shut is shut and shelving parked in front of a disconnect is in front of it. Sketching the layout in the margin before reading the options makes the wall much easier to see than it is in a sentence.

NEC 2026 110.29

D. No, because the distance half of the test fails

This is the mirror image of the wall case. Visibility passes and distance fails, and again the pair fails. Marking the disconnect and keeping the aisle clear are both good practice and neither one is a condition in the rule, which is why two of the wrong options sound like a compromise an inspector might accept.

NEC 2026 110.29

B. The provisions for locking remain in place whether or not a lock is installed

The substitution only works if the locking hardware is there on the day the next person arrives, which is usually years after the installer left. A hasp that travels in somebody's van is not a provision for locking, and a breaker that only accepts an accessory nobody left on site is not lockable in the sense the code means. The lock itself does not have to be installed.

NEC 2026 110.25

C. A cord and plug connection

A cord pulled out of a receptacle is its own proof that the circuit is open, so the locking provision does not have to remain in place without the lock in that case. The industrial and over 1000 volt conditions are real, but they appear as conditions on other permissions in the motor and air conditioning articles rather than on this one. Reading an exception under the rule it actually modifies is the habit being tested.

NEC 2026 110.25

A. An individual disconnecting means, located in sight from the controller

Each controller gets its own disconnect and it goes where somebody working at the controller can see it. That is a separate requirement from the one protecting somebody working at the motor, and the two can be satisfied by one device only when that device is in sight from both places. The branch circuit protective device is a different element in the circuit and does not stand in for this.

NEC 2026 430.102(A)

D. A single disconnecting means for the group, located in sight from those controllers

The exception recognizes that one machine is one thing to work on, so one disconnect in sight from the group of controllers does the job the rule was written for. The in sight requirement does not go away, it just applies to the group. An out of sight disconnect with a label is a different permission, and it belongs to the circuits over 1000 volts.

NEC 2026 430.102(A)

B. In sight from the motor location and the driven machinery location

Two locations, not one. Somebody may be working at the motor or at the machine the motor drives, and a conveyor or a pump can put those in different places. The wording is why a disconnect at the motor on a piece of equipment whose drive end is around a corner can still fail. The controller end is protected by a different subsection.

NEC 2026 430.102(B)

C. Yes, if it is in sight from the motor location and the driven machinery location

One device can satisfy both requirements when it happens to be in sight from all three places, the controller, the motor and the driven machinery. That is common on a small package unit and rare on a long conveyor. Distance alone is not the test, since the visibility half still has to hold at each location.

NEC 2026 430.102(B)

A. The controller disconnect is lockable, and locating a motor disconnect is impracticable or introduces added hazards, or the site is an industrial installation with written safety procedures

The exception buys the same protection a different way, so it starts by requiring the controller disconnect to be lockable open. Then one of two situations has to hold, either the location is impracticable or hazardous, or the installation is industrial with written procedures and qualified persons. Horsepower on its own does not open the exception, though very large motors appear in the informational note as an example of added hazard.

NEC 2026 430.102(B), 110.25

A. It opens all ungrounded supply conductors, no pole can be operated independently, and it cannot be closed automatically

All three conditions sit in one short section. The same section permits the disconnect to share an enclosure with the controller, which is why a combination starter is one box with two functions inside it. A device that could reclose on its own would defeat everything the disconnect exists for, which is the reason that sentence is there.

NEC 2026 430.103

C. Article 440, which modifies the motor rules rather than replacing them

The scope of that article covers electric motor-driven air conditioning and refrigerating equipment and the circuits and controllers for it, and it adds what is needed for a sealed compressor that has no horsepower rating for the motor tables to work from. It modifies Article 430 rather than displacing it, so a rooftop unit can pull in both. Article 404 governs switches as devices, not where a disconnect goes.

NEC 2026 440.1, 440.14

D. At least one of them has to be readily accessible

The section is one line and it asks for at least one. That is a lower bar than it looks, because every disconnect in the circuit between the feeder or branch circuit and the motor still has to meet the type and rating sections. Readily accessible means reachable without climbing over or removing obstacles, which is a separate idea from being in sight.

NEC 2026 430.107, 430.108

D. 28 amperes

A general-use switch used this way needs an ampere rating of not less than twice the full-load current, so 14 doubled is 28. The first figure is 115 percent, which is the general rating rule for a disconnecting means, and the second is 125 percent, which is the conductor rule. Three plausible percentages of the same current is how this item is built.

NEC 2026 430.109(A)

A. 16 amperes

The condition on this permission runs the other way from the general-use switch rule. The motor full-load current has to be not more than 80 percent of the switch rating, so a 20 ampere switch tops out at 16 amperes. The switch also has to be one suitable for alternating current only rather than the general-use ac and dc kind.

NEC 2026 430.109(A)

B. 16.1 amperes

The general rating rule is 115 percent of the full-load current, so 14 times 1.15 is 16.1. That current comes from the motor table rather than from the nameplate, since the table values are what the code uses for conductor ampacity, switch ratings and branch circuit protection. An exception releases a listed unfused motor-circuit switch with a horsepower rating at or above the motor from the 115 percent figure.

NEC 2026 430.110(A), 430.6(A)(1)

D. A single disconnecting means for the group, rated for the combined load

The general rule gives each motor an individual disconnecting means, and the exception lets one device serve a group under any one of three conditions, the first of which is several motors driving parts of a single machine or piece of apparatus. The single device is then rated for the combined load. Horsepower does not enter into which condition applies.

NEC 2026 430.112

A. Within sight from and readily accessible from the equipment, and it is permitted to be on or within the equipment

That section asks for two things at once, line of sight and ready access from the equipment, and it then permits the disconnect to be mounted on or inside the unit itself. It also requires the working space rules to be met at the disconnect, which is easy to overlook on a crowded roof curb. A device in a panelboard two rooms away is in sight of nobody working on the unit.

NEC 2026 440.14

D. Both are prohibited, since the section bars mounting on panels designed to allow access to the equipment and bars a location that obscures the nameplate

The second paragraph of that section carries two prohibitions in one sentence and both are aimed at the same practical problem, that a service technician needs the panel to come off and the nameplate to be readable while the disconnect stays where it is. Being within sight does not rescue either one. This is the kind of detail that gets tested because it is invisible in a summary.

NEC 2026 440.14

C. Its purpose, together with the identification and location of the circuit source that supplies it

The marking rule has two halves and the second one applies in other than one- or two-family dwellings. Both halves fall away where the disconnect is located and arranged so that the purpose, or the source, is evident on its own. The marking also has to be durable enough for the environment it sits in, which rules out a felt pen on a rooftop.

NEC 2026 110.22(A)

B. It simultaneously disconnects all ungrounded service conductors it controls from the premises wiring system

Simultaneous opening is the point of the section, since a service disconnect that could leave one leg energized would put a working electrician in exactly the position the disconnect exists to prevent. A separate section handles the grounded conductor, requiring other means in the service equipment where the disconnect does not open it, and permitting a terminal or bus with pressure connectors for that purpose.

NEC 2026 230.74, 230.75

B. Yes, provided that pole cannot be opened without simultaneously disconnecting all conductors of the circuit

The permission exists so a switch can carry a pole in the grounded conductor, and the condition is what keeps it safe, since a grounded conductor opened while the ungrounded ones stay closed leaves the load energized and the return path broken. That condition is a design feature of the device rather than something field wiring can supply. It sits alongside the rule that no pole of the disconnect may be operated independently.

NEC 2026 430.105, 430.103

D. In a readily accessible outdoor location, either on the dwelling or within sight of it

The 2026 rule splits by occupancy. One- and two-family dwellings take a readily accessible outdoor location, on the building or within sight of it by the same in sight rule used everywhere else, with an exception where an emergency disconnect is installed instead. The inside near the entrance option belongs to other occupancies. Bathrooms are barred outright for service disconnecting means.

NEC 2026 230.70(A)

C. One, unless the conditions permitting two to six are met

The 2026 rule starts at one disconnect per service and then opens a path to two through six under a listed set of arrangements, such as separate enclosures each holding a single disconnect or switchgear with each disconnect in its own compartment. Disconnects that only cut power monitoring equipment, a surge device or certain control circuits are not counted against the number. Grouping on its own does not buy an unlimited count.

NEC 2026 230.71