Contractor Practice Exam Questions

CA D04 Central Vacuum Systems Contractor Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• What is the primary purpose of a central vacuum system in a building?
• Increase indoor humidity
• Remove dust and debris efficiently
• Provide fresh air
• Heat the building

Answer: B. Remove dust and debris efficiently

Rationale: Central vacuum systems are designed to remove dust, dirt,

and debris from living or working spaces efficiently, improving indoor air quality.

• Which material is most commonly used for central vacuum system

piping?

• Copper

B. PVC

• Steel
• Aluminum

Answer: B. PVC

Rationale: PVC is lightweight, corrosion-resistant, and smooth inside,

reducing friction and maintaining suction efficiency.

• What is the recommended pipe diameter for a standard residential

central vacuum system?

• 1 inch
• 2 inches 1 / 3

• 3 inches
• 4 inches

Answer: B. 2 inches

Rationale: A 2-inch diameter provides sufficient airflow for most

residential systems without excessive pressure loss.

• Where should the power unit of a central vacuum system typically be

installed?

• In the kitchen
• In a garage, basement, or utility room
• In a living room
• On a balcony

Answer: B. In a garage, basement, or utility room

Rationale: Installing the power unit in an out-of-the-way area reduces

noise and allows easy access for maintenance.

• What is the maximum recommended horizontal run for PVC piping in a

central vacuum system without an intermediate in-line booster?

• 50 feet
• 100 feet
• 150 feet
• 200 feet

Answer: B. 100 feet

Rationale: Longer runs can reduce suction performance. 100 feet is

generally recommended for standard systems.

• Which type of central vacuum hose connection is most common?
• Threaded
• Slip-fit with locking ring
• Welded
• Snap-on tape

Answer: B. Slip-fit with locking ring

Rationale: Slip-fit connections with locking rings are easy to install

and remove while ensuring an airtight seal.

• What is the typical voltage requirement for a residential central vacuum

power unit?

A. 110-120V

B. 120V

C. 220V

D. 240V 2 / 3

Answer: B. 120V

Rationale: Most residential units are designed for standard 120V

circuits.

• Which of the following is a key advantage of a central vacuum system

over portable vacuum cleaners?

• Cheaper initial cost
• Reduced noise and improved indoor air quality
• No need for maintenance
• Portable for outdoor use

Answer: B. Reduced noise and improved indoor air quality

Rationale: Central vacuum systems are quieter since the motor is

remote, and exhausts outside or through a filter.

• How often should the central vacuum canister be emptied under normal

residential use?

• Weekly
• Every 6–12 months
• Every 2–3 years
• Only when suction drops to zero

Answer: B. Every 6–12 months

Rationale: Frequency depends on usage, but yearly maintenance is

typical for average homes.

• Which standard should contractors reference for electrical wiring

of central vacuum systems?

A. ISO 9001

• National Electrical Code (NEC)
• OSHA General Industry Standard

D. ASTM D1785

Answer: B. National Electrical Code (NEC)

Rationale: All electrical installations in the U.S. must comply with the

NEC for safety.

• What is the ideal slope for horizontal central vacuum piping

runs?

• Level
• 1/4 inch per 10 feet toward the power unit
• 1 inch per foot
• Downward only at elbows

Answer: B. 1/4 inch per 10 feet toward the power unit

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