Controls & Disconnects — Texas Master Practice Questions

6 questions · 4% of the NEC Knowledge exam

Worked questions

1. A healthcare facility is required to install an emergency lighting system. According to the 2026 NEC, what is the minimum required duration of illumination for emergency lighting in this facility?

A1 hour
B90 minutes
2 hours
D3 hours

Exam tip

Remember that healthcare facilities have specific requirements for emergency systems, including lighting, that are more stringent than general occupancy requirements.

Why C is correct

Healthcare facilities are required to have emergency lighting systems with a minimum duration of 2 hours of illumination according to 2026 NEC Article 700.10(A)(1). Option A, B, and D are incorrect as they do not meet the specific requirements for healthcare facilities.

2. A proposed 100-ampere branch circuit is intended to supply equipment whose instructions call for 125-ampere overcurrent protection. The circuit design has not been checked for that protection. What should be done before selecting a device?

AInstall a 100-ampere breaker and ignore the equipment instructions
Resolve the mismatch by checking conductor capacity, equipment instructions and applicable protection rules
CInstall a 125-ampere breaker without reviewing the circuit
DInstall a 125-ampere fuse without reviewing the circuit

Where to look it up

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.304

Why B is correct

The stated ratings reveal a mismatch that requires design review. Protection must be compatible with conductor and equipment capacity, while listed equipment instructions and any applicable specific permissions must also be checked. Choosing a breaker or fuse solely from one rating does not establish a suitable circuit.

3. In a motor control center, the disconnecting means for each circuit must be accessible from the point of control. According to the 2026 NEC, what type of disconnecting means is typically used for this purpose?

Circuit Breaker
BGround Fault Circuit Interrupter (GFCI)
CIsolating Transformer
DManual Motor Starter

Exam tip

Familiarize yourself with the types of disconnecting means required in various applications as per the NEC.

Why A is correct

Circuit breakers are commonly used as disconnecting means in motor control centers, as they provide the necessary isolation from the source of power and are accessible from the point of control. GFCIs, isolating transformers, and manual motor starters are not typically used as primary disconnecting means for this purpose.

4. What electrical hazard is an arc-fault circuit interrupter (AFCI) designed to detect and interrupt to help reduce fire risk?

AEvery possible cause of equipment overheating
Hazardous arcing faults in the protected circuit
CA loss of utility power
DThe absence of an equipment grounding conductor

Where to look it up

https://www.cpsc.gov/s3fs-public/5133(1).pdf

Why B is correct

AFCIs detect hazardous arcing conditions and interrupt the circuit to help reduce associated fire risk. This is distinct from the shock-protection purpose of GFCIs. An AFCI does not prevent every electrical fire or replace proper wiring and other required protection.

5. In an office building, a series of lighting fixtures are being installed. According to the 2026 NEC, what is the maximum spacing between luminaires that can be connected in series for control purposes?

A3 feet
B5 feet
C7 feet
10 feet

Exam tip

Understand the limitations and requirements for the installation of lighting fixtures and control systems as outlined in the NEC.

Why D is correct

The NEC specifies that the maximum spacing between luminaires connected in series for control purposes is 10 feet. Options A, B, and C are incorrect as they exceed the maximum spacing allowed.

6. When installing a grounding electrode in residential construction, the NEC requires a minimum length of 8 feet for the electrode. What is the primary reason for this requirement?

To increase the surface area for better grounding
BTo ensure the electrode is below the frost line
CTo provide a sufficient length for the bonding wire
DTo minimize the risk of corrosion

Exam tip

Understand the importance of grounding and bonding in residential construction and the specific requirements outlined in the NEC.

Why A is correct

The primary reason for the minimum length requirement of 8 feet for grounding electrodes in residential construction is to increase the surface area, which enhances the grounding effectiveness. The other options are not the primary reasons for this requirement.

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Controls & Disconnects — Texas Master Practice Questions

Worked questions

1. A healthcare facility is required to install an emergency lighting system. According to the 2026 NEC, what is the minimum required duration of illumination for emergency lighting in this facility?

2. A proposed 100-ampere branch circuit is intended to supply equipment whose instructions call for 125-ampere overcurrent protection. The circuit design has not been checked for that protection. What should be done before selecting a device?

3. In a motor control center, the disconnecting means for each circuit must be accessible from the point of control. According to the 2026 NEC, what type of disconnecting means is typically used for this purpose?

4. What electrical hazard is an arc-fault circuit interrupter (AFCI) designed to detect and interrupt to help reduce fire risk?

5. In an office building, a series of lighting fixtures are being installed. According to the 2026 NEC, what is the maximum spacing between luminaires that can be connected in series for control purposes?

6. When installing a grounding electrode in residential construction, the NEC requires a minimum length of 8 feet for the electrode. What is the primary reason for this requirement?

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