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Contractor Licensing · CMC

Tennessee Contractor Full Mechanical Contractor Examination Practice Test

Mechanical contracting draws on HVAC, refrigeration, ventilation, fuel-burning equipment, and the installation practices that keep these systems safe and effective. The available practice material includes motor selection and electrical isolation, duct construction, refrigerant-line brazing, condensate drainage, fire-damper placement, and combustion-air and venting conditions.

Exam overview

Exam providerTennessee Board for Licensing Contractors
Exam codeCMC
CategoryContractor Licensing

About the Tennessee Contractor Full Mechanical Contractor Examination Exam

Mechanical work requires matching replacement motors to equipment ratings and isolating power so machinery cannot start unexpectedly during service. Duct decisions affect airflow, noise, and pressure loss: sealed joints limit leakage, while gradual transitions help avoid unnecessary turbulence. Refrigerant piping work calls for clean, properly prepared joints; flowing dry nitrogen during brazing helps limit internal oxidation. Drain-pan slope and outlet placement matter because standing condensate can interfere with drainage. Mechanical systems also interact with building fire protection: a required fire damper helps maintain a rated wall or floor assembly where a duct penetrates it. For fuel-burning appliances, adequate combustion air and unobstructed, correctly configured venting are central to safe operation. These topics call for reading equipment information, recognizing installation hazards, and connecting component details to system performance.

Sample Practice Questions

Review a selection from this exam's published US Practice Tests practice bank.

Question 1

A fan motor is being replaced with one that has a different rated horsepower. What should be checked before installation?

  1. AThat the replacement motor’s electrical and mechanical ratings are compatible with the equipment and its load
  2. BThat the replacement motor has the same paint color as the original
  3. CThat the motor is installed without checking the fan’s rotation direction
  4. DThat the motor’s rated speed is ignored if its frame fits
Show answerCorrect answer: A

A replacement motor must be suitable for the equipment load and compatible with the electrical supply, speed, mounting, and other relevant operating requirements. Physical fit alone does not establish compatibility.

Question 2

A technician is preparing to work on a motor-driven mechanical unit. Which action is the safest way to prevent unexpected electrical startup during service?

  1. ATurn the thermostat to its lowest setting only
  2. BApply lockout/tagout to the energy-isolating device and verify the equipment is de-energized
  3. CRemove the equipment nameplate
  4. DDisconnect the motor grounding conductor
Show answerCorrect answer: B

Lockout/tagout helps prevent equipment from being energized unexpectedly. A qualified worker should isolate the relevant energy sources and verify the absence of hazardous voltage before beginning work.

Question 3

Why should a duct system’s joints and seams be sealed?

  1. ATo reduce uncontrolled air leakage and help the system deliver its intended airflow
  2. BTo increase the duct’s electrical conductivity
  3. CTo eliminate the need for duct supports
  4. DTo prevent all temperature change in the air stream
Show answerCorrect answer: A

Sealing duct joints limits leakage, which can waste conditioned air and impair system performance. Sealing methods and materials should be suitable for the duct application and comply with applicable requirements.

Question 4

A technician is brazing copper refrigerant tubing. Why is a small flow of dry nitrogen commonly passed through the tubing during brazing?

  1. ATo increase the refrigerant pressure before charging
  2. BTo reduce internal oxidation and scale formation
  3. CTo cool the joint rapidly after heating
  4. DTo remove moisture from the system without evacuation
Show answerCorrect answer: B

A low flow of dry nitrogen displaces oxygen inside the tubing, helping prevent copper oxide scale from forming during brazing. Nitrogen flow does not replace proper evacuation or charging procedures.

Question 5

What is the purpose of a fire damper where an air duct passes through a fire-resistance-rated wall or floor, when one is required by the design and code?

  1. ATo help limit fire spread through the duct opening by closing under specified conditions
  2. BTo increase outdoor-air intake during normal operation
  3. CTo prevent water hammer in nearby piping
  4. DTo balance refrigerant flow between circuits
Show answerCorrect answer: A

A fire damper is a life-safety device intended to help maintain the fire-resistance function of a rated assembly at a duct penetration. Its type, location, and installation must follow the approved design and applicable code.

Question 6

A cooling coil is installed above a drain pan outlet. Which feature helps ensure condensate flows to the outlet rather than pooling in the pan?

  1. AA pan sloped toward the drain connection
  2. BA larger refrigerant suction line
  3. CA closed isolation valve on the drain
  4. DA higher fan speed
Show answerCorrect answer: A

A drain pan should be arranged with an appropriate slope toward its outlet so condensate can drain rather than stagnate or overflow. Installation details should follow the equipment instructions and applicable requirements.

Question 7

When laying out a rectangular sheet-metal duct transition, what design practice generally helps reduce airflow noise and pressure loss?

  1. AUse gradual transitions rather than abrupt changes in duct area
  2. BMake the transition as short and abrupt as possible
  3. CAdd sharp internal corners to redirect the airflow
  4. DReduce the duct area at every fitting regardless of airflow requirements
Show answerCorrect answer: A

Gradual changes in duct area generally reduce flow separation and turbulence compared with abrupt transitions, which helps limit pressure loss and noise. Transition dimensions should still suit the system's airflow and space constraints.

How to use this practice test

Access is free. A session draws up to 20 random questions from the 50-question practice bank and displays results when the session ends. Use each question to identify the mechanical principle behind the decision—such as motor compatibility, duct airflow, brazing practice, drainage, or combustion safety—and revisit any missed concepts before another session.

Preparation tips

  • Compare a replacement motor’s horsepower and other nameplate ratings with the equipment requirements before installation; consider how a mismatch can affect operation.
  • Practice identifying electrical energy-isolation steps that prevent unexpected motor startup during service.
  • Review why duct sealing and gradual rectangular transitions affect leakage, airflow noise, and pressure loss.
  • Study copper-tube preparation for soldering and the purpose of dry-nitrogen flow during refrigerant-line brazing.
  • Trace condensate drainage, required fire-damper locations, and combustion-air and venting conditions in mechanical-system layouts.
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