14.1 Motor Disconnects & Controllers
Key Takeaways
- NEC Article 430 Part IX requires a disconnecting means for motors and for motor controllers; Article 100 defines “in sight from” as visible and not more than 50 ft distant
- NEC 430.102(A) generally requires a disconnect in sight from the controller; 430.102(B) generally requires a disconnect in sight from the motor and driven machinery, with a locked-open exception when the controller disconnect is not in sight from the motor
- NEC 430.103 requires the disconnect to open all ungrounded supply conductors simultaneously and to be designed so it cannot be closed automatically
- NEC 430.109 and 430.110 set permitted disconnect types and minimum ampere/horsepower ratings (commonly at least 115% of motor full-load current for many motor disconnects)
- Article 430 Part VII covers controllers: ratings (430.83), grounded-conductor rules (430.84/430.85), and limited cases where a branch-circuit device or attachment plug may serve as the controller
Why Disconnects & Controllers Matter on the Arkansas JW Exam
The Arkansas Journeyman Electrician exam (Prov / ADLL, NEC 2023, 60 questions, 3 hours, 70% pass) weights Motors and Controls at 7 items. Chapter 13 covered how to size motor branch-circuit conductors, overload devices, and short-circuit/ground-fault protection from Article 430 Parts II–V. This section covers the hardware that starts and stops the motor safely: disconnecting means (Part IX) and controllers (Part VII).
Open-book Prov stems in this cluster almost always turn on location (“in sight from”), what the disconnect must open, and whether a device is allowed to serve as both controller and disconnect. Tab Article 100 (in sight from), 430.101–430.113, and 430.81–430.90 as one cluster. Do not answer a disconnect location question from feeder rules in Article 225 or service rules in Article 230.
Vocabulary Before You Open Part IX
| Term | Exam-useful meaning |
|---|---|
| Controller | Device or group of devices that governs electric power to the motor (starter, contactor + overload, VFD as controller, etc.) |
| Disconnecting means | Device that disconnects the motor / controller from the supply conductors |
| In sight from | Visible and not more than 50 feet distant (Article 100) |
| Motor control circuit | Circuit that carries electric signals directing controller performance (taught in §14.2) |
Trap: a magnetic starter is usually the controller. The disconnect may be a separate fused switch, circuit breaker, or a combination starter that includes both functions. Read the stem’s exact word.
Scope — 430.101
Part IX covers disconnecting means for motors and controllers. It answers: where must the disconnect be, what must it open, what types are permitted, and how is it rated? It does not replace overload rules in Part III or branch-circuit short-circuit/ground-fault rules in Part IV. If the stem asks “maximum fuse size for motor branch-circuit protection,” stay in 430.52 / Tables — not Part IX.
Location of the Disconnect — 430.102 (High-Yield)
Controller disconnect — 430.102(A)
A disconnecting means shall be located in sight from the controller location. Classic exceptions (verify exact text when the stem invokes them) include:
- Where the disconnect is capable of being locked in the open position and meets the section’s lockable-disconnect conditions.
- Special equipment arrangements listed in the exceptions (for example, certain elevator / industrial process situations described in the Code).
On Prov, if the stem shows a starter in a mechanical room and asks for the normal rule, look for a disconnect visible and ≤50 ft from that starter — not “anywhere in the building.”
Motor disconnect — 430.102(B)
A disconnecting means shall be located in sight from the motor location and the driven machinery location. Important practical pairing with (A):
- Often one properly located disconnect serves both controller and motor when both are in sight of that disconnect.
- Where the controller disconnect is not in sight from the motor, 430.102(B) generally still requires a motor disconnect in sight — unless the controller disconnect is lockable open under the stated conditions (the “locked-open” path many stems test).
Workflow under time pressure:
- Find the controller and the motor on the sketch/description.
- Ask whether one device is in sight of both.
- If not, decide whether the stem is testing the second disconnect requirement or the lockable controller disconnect exception.
- Confirm “in sight” with Article 100 (visible + 50 ft), not a remembered “100 ft” folklore number.
Operation & Indication — 430.103 / 430.104
430.103 requires the disconnecting means to open all ungrounded supply conductors and to be designed so that no pole can be operated independently in a way that defeats simultaneous opening of those conductors. The disconnect must be designed so it cannot be closed automatically. That is why a plain “start” pushbutton is not a disconnecting means.
430.104 addresses readily accessible / indication themes in coordination with other Article 430 rules — on the exam, prefer options that keep the disconnect operable without climbing into unsafe positions or defeating lockout.
Grounded conductors are handled carefully: motor disconnects focus on ungrounded conductors. Do not invent a requirement that every motor disconnect must open the neutral unless the stem points to a specific rule that does.
Types of Disconnecting Means — 430.109
430.109 lists permitted disconnect types. Journeyman-frequency examples include:
- A horsepower-rated motor-circuit switch
- A circuit breaker molded-case or other permitted CB arrangement
- A molded-case switch
- An instantaneous-trip circuit breaker that is part of a listed combination with a controller (where permitted)
- A self-protected combination controller
- For portable motors, an attachment plug and receptacle (within the horsepower / ampere limits stated)
- For stationary motors of ⅛ horsepower or less, the branch-circuit overcurrent device may be permitted to serve as the disconnect under the section’s conditions
Always open 430.109 when the stem asks “which of the following is an acceptable motor disconnect?” — the distractors are usually feeder breakers remote from the motor, horsepower-underrated general-use switches, or devices that cannot be locked open when the exception path requires locking.
Ampere Rating / Interrupting Capacity — 430.110
430.110 is a calculation/lookup favorite:
- The disconnecting means for motor circuits rated 1000 volts or less generally must have an ampere rating of not less than 115% of the motor full-load current rating determined from Article 430 tables (not a random nameplate guess when the Code points you to Tables 430.247–430.250).
- Horsepower-rated switches must be rated for the motor horsepower (and voltage).
- Combination loads, multi-motor circuits, and torque-motor / locked-rotor special cases have additional rating paths — open the applicable subsection when the stem is not a single ordinary motor.
Prov pattern: “Minimum ampere rating of the motor disconnect” → find FLC from the correct table → apply 115% → select the next device rating that meets or exceeds that value if the options are standard switch sizes.
Do not confuse 115% disconnect rating with:
- 125% conductor sizing (430.22),
- overload trip settings (430.32),
- or maximum branch-circuit short-circuit/ground-fault device percentages (430.52).
Those percentages live in different Parts for different purposes.
Controllers — Part VII Essentials
General & design — 430.81 / 430.82
Controllers must be suitable for starting and for interrupting the motor’s locked-rotor current where required by the equipment design rules. A controller is not automatically a disconnect unless it also meets Part IX (or is a listed combination that is marked/used for both functions).
Ratings — 430.83
430.83 requires controller ratings not less than the motor horsepower / current as applicable. Exceptions allow certain circuit breakers and other devices to serve as controllers for limited motor sizes. Stationary motors ⅛ HP or less may use the branch-circuit protective device as the controller under stated conditions. Portable motors may use a cord-and-plug arrangement as the controller within limits.
Grounded conductors — 430.84 / 430.85
430.84: the controller need not open the grounded conductor. 430.85 restricts switching of grounded conductors when a switch is used in the grounded conductor — typically only if the ungrounded conductors are simultaneously opened. Exam trap: “must always break the neutral” is usually wrong for ordinary motor controllers.
Number of conductors opened / arrangement
Controllers generally open enough conductors to halt the motor. Multi-speed / two-winding arrangements and reversible controllers have specific construction expectations — if the stem describes a reversing starter, look for simultaneous opening of the supply conductors feeding that controller, not a single-leg “trick” stop.
Combination Starters & “One Device, Two Jobs”
Many commercial installations use a combination motor controller: disconnect + branch-circuit short-circuit/ground-fault protection + controller + overload relay in one enclosure. On the exam:
- Confirm the assembly is listed for the combined functions claimed.
- Still apply 430.102 location rules to the combination enclosure relative to the motor.
- Still size power conductors and OCP from Parts II–IV; the combination label does not rewrite Table 430.52.
Timed Open-Book Tips for §14.1
- Tab 100 (in sight), 430.102, 430.109, 430.110, 430.83 together.
- Classify the stem: location, type permitted, ampere/HP rating, or controller vs disconnect identity.
- Recycle FLC from Chapter 13 tables when 430.110 needs a number.
- Never use service-disconnect rules (230.70) to answer a motor disconnect stem.
- If both “controller” and “motor” are named, run the 430.102(A) and (B) checklist before picking an exception.
Per Article 100, what does “in sight from” mean for locating a motor or controller disconnect?
Under NEC 430.102(A), where must a motor controller’s disconnecting means generally be located?
For many motor circuits 1000 volts or less, NEC 430.110 generally requires the disconnecting means ampere rating to be not less than what percentage of the motor full-load current?
Which statement best matches NEC 430.84 regarding motor controllers and the grounded conductor?