Short answer: A controller starts and stops the motor. A disconnecting means isolates the motor and controller from the supply so they can be worked on. Each controller needs a disconnect in sight from it, and the motor normally needs a disconnect in sight from the motor too. The disconnect must open all ungrounded supply conductors and show whether it is on or off. Controllers and disconnects are usually horsepower rated, and in some cases one switch can serve as both.
PSI lists motors in the Motors and Generators subject area of the Texas Journeyman exam (5 scored NEC Knowledge questions and 2 scored Calculations questions) and disconnecting means in Control Devices and Disconnecting Means (1 scored question in each part). PSI does not say how many cover motor disconnects alone. The Texas Journeyman Practice Pack has 1,000 original questions and 10 timed mock exams in the real two-part format, with step-by-step solutions for every calculation. Try free practice questions without signing up. Get the full pack for US$39 with one payment.
Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the ideas in our own words and do not reproduce NEC text. Check every rule and table value in your own 2026 NEC, and follow your supervisor and the local inspector.
Controller vs disconnect
| Controller | Disconnecting means | |
|---|---|---|
| Job | Starts and stops the motor in normal use | Isolates the motor and controller from the supply |
| Must open every ungrounded conductor? | No, unless it is also used as the disconnect (NEC 430.84) | Yes, all ungrounded supply conductors at once (NEC 430.103) |
| Typical devices | Magnetic starter, manual motor starter, switch | Fused or unfused switch, circuit breaker |
| Rating | Horsepower rating not lower than the motor (NEC 430.83(A)(1)) | Usually horsepower rated |
Where the disconnects go
- Controller disconnect. A disconnecting means is required for each controller, located in sight from the controller (NEC 430.102(A)). In sight means visible and not more than 50 feet away.
- Motor disconnect. A disconnect is also required in sight from the motor and its driven machinery (NEC 430.102(B)). The controller disconnect can serve this role if it is in sight from the motor too.
- Exception. Where a disconnect at the motor is impracticable or would add a hazard, it can be left out if the controller disconnect can be locked open as the code describes (NEC 430.102(B) Exception). Read the full list of conditions in your NEC.
- Accessibility. At least one of the disconnecting means must be readily accessible (NEC 430.107).
What the disconnect must do
- Open all ungrounded conductors together, with no pole that can be operated on its own (NEC 430.103).
- Show its position. It must plainly indicate whether it is open (off) or closed (on) (NEC 430.104).
- Disconnect every source. Where a motor and its equipment get power from more than one source, each source needs its own disconnecting means (NEC 430.113).
Small motors and special cases
- 1/8 hp or less, stationary. The branch circuit overcurrent device can serve as the disconnect (NEC 430.109(B)).
- Cord-and-plug connected. A horsepower-rated attachment plug and receptacle, or similar connector, can serve as the disconnect, with some exceptions for appliances, room air conditioners and small portable motors (NEC 430.109(F)).
- Small portable motors. A portable motor of 1/3 hp or less can use a plug and receptacle as its controller (NEC 430.81(B)).
- General-use switch for small motors. For a stationary motor of 2 hp or less at 300 V or less, a general-use switch rated at least twice the motor’s full-load current can be the controller (NEC 430.83(C)(1)). Example: a 1 hp, 115 V single-phase motor has a table full-load current of 16 A (NEC Table 430.248), so the switch must be rated at least 32 A.
When one switch can be both
A switch or circuit breaker can serve as both the controller and the disconnect if it meets the controller rules, opens all ungrounded conductors, and has overcurrent protection in each ungrounded conductor (NEC 430.111(A)). A simple horsepower-rated switch on a small motor is the common example.
Worked example: one disconnect for three motors
Each motor normally has its own disconnect. One disconnect may serve a group of motors only under the conditions in the exceptions to 430.112, such as several motors driving parts of one machine (NEC 430.112 Exception (1)). When sharing is allowed, the disconnect is rated for the combined load (NEC 430.110(C)(1)).
Assume three 460 V three-phase motors, 25 hp, 20 hp and 10 hp, drive parts of one machine and are allowed to share one disconnect. From Table 430.250:
| Motor | Full-load current at 460 V |
|---|---|
| 25 hp | 34 A |
| 20 hp | 27 A |
| 10 hp | 14 A |
| Total | 75 A |
- Add the full-load currents: 34 + 27 + 14 = 75 A.
- Find the smallest horsepower in the 460 V column with a full-load current of at least 75 A: 60 hp (77 A). 50 hp is 65 A, which is too low.
- 60 hp is not yet the final rating. Repeat the check with the locked-rotor currents of the motors and the locked-rotor table, then use the larger of the two horsepower results. This example stops at the full-load step, so the final rating depends on that second check.
Confirm the table values in your own 2026 NEC before you rely on them.
Check yourself
- Does a magnetic starter have to open every ungrounded conductor? No, unless it also serves as the disconnecting means.
- How far away can a disconnect be and still be in sight? Visible and not more than 50 feet.
- Can the branch circuit breaker be the disconnect for a 1/8 hp stationary motor? Yes.
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Find Article 430 Part IX faster on exam day
NFPA 70, National Electrical Code, 2026 Edition (softcover). Highlight the in sight rules, the disconnect rating rules and Tables 430.248 and 430.250, and practice moving between a rule and a motor current table. The Texas exam is open book. PSI allows a soft-bound NEC with highlighting, underlining and notes made in advance. Loose-leaf, spiral-bound and ring-bound copies are not allowed, and only permanent index tabs made or supplied by the NEC publisher are permitted; homemade and third-party tabs are not.
FAQ
Does a motor need a disconnect within sight?
Generally yes. The controller needs a disconnect in sight from it, and a disconnect is also required in sight from the motor, with a limited exception where the controller disconnect can be locked open.
What does “in sight from” mean in the NEC?
Visible and not more than 50 feet from the equipment.
Can a circuit breaker be the motor disconnect?
Yes. A circuit breaker is one of the permitted disconnecting means, and it must open all ungrounded supply conductors.
Is this on the Texas Journeyman exam?
PSI lists motors in Motors and Generators (5 scored NEC Knowledge and 2 scored Calculations questions) and disconnecting means in Control Devices and Disconnecting Means (1 scored question in each part).
Sources checked October 2026
- PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
- NFPA 70, National Electrical Code, 2026 Edition, Article 430 Parts VII and IX, Tables 430.248 and 430.250
