Tennessee CMC-C HVAC Contractor License Exam Practice Test

Prepare for the Tennessee CMC-C HVAC/Refrigeration Contractor Exam with a focused bank of original practice questions and detailed answers covering the technical areas candidates need to review before test day. This study material is designed for HVAC and refrigeration contractors working toward the Tennessee CMC-C classification, with practical scenarios involving heating, cooling, refrigeration, fuel gas, piping, controls, electrical concepts, load calculations, air distribution, ventilation, and safety.

The practice set is built around the current CMC-C examination scope and is intended to help you test your knowledge, locate weak areas, and become more comfortable working through technical questions under time pressure. The product is independent preparation material and is not an official Tennessee Board or Prov examination.

How This Exam Practice Test Helps You Prepare

This practice test gives you repeated exposure to the types of technical decisions and calculations relevant to HVAC/refrigeration contracting. Each question is followed by an answer and explanation so you can learn from both correct and incorrect choices.

• Practice HVAC and refrigeration exam-style questions in multiple-choice format
• Review heating, cooling, refrigeration, piping, controls, and mechanical-system concepts
• Work through practical troubleshooting situations rather than relying only on memorization
• Strengthen understanding of fuel-gas systems and combustion-related problems
• Review electrical concepts used in HVAC equipment and motor troubleshooting
• Practice load-calculation and sensible-heat calculations
• Study air distribution, ductwork, ventilation, exhaust, and system-pressure problems
• Review safety situations involving electrical work, pressure testing, refrigerants, hot work, and hazardous energy
• Use detailed explanations to understand why an answer is correct and why the alternatives are not

The questions are particularly useful for identifying topics that need another review before scheduling the Tennessee trade examination.

What Is the Tennessee CMC-C HVAC/Refrigeration Contractor Exam?

The CMC-C classification covers HVAC and refrigeration work, including installation, alteration, repair, replacement, and servicing of heating, ventilation, air-conditioning equipment, refrigeration systems, HVAC-related gas piping, ductwork, exhaust systems, controls, heat pumps, geothermal and solar thermal HVAC systems, and related refrigeration piping.

According to the current Prov Candidate Information Bulletin:

• Exam: Tennessee CMC-C — HVAC/Refrigeration Contractor
• Questions: 100
• Time allowed: 2 hours
• Format: Computerized and open-book
• Passing standard: 73%
• Exam fee: $53 per attempt through Prov
• Trade exam provider: Prov began administering Tennessee contractor examinations July 1, 2026
• Testing options: Prov testing centers and Examroom remote proctoring are available
• Business & Law: New contractor applicants also take the Tennessee Business & Law examination in addition to an applicable trade exam

The current CMC-C outline contains 100 questions distributed across 12 subject areas, making it important to prepare broadly rather than concentrating on refrigeration or air conditioning alone.

Tennessee CMC-C Exam Topics and Subject Areas

The current Prov outline identifies the following CMC-C areas:

The largest portion is Air Distribution and Venting, followed by Piping, Fuel Gas Systems, HVAC Equipment, and Refrigerants and Oils. That distribution makes it important to study the complete mechanical system rather than preparing only for refrigeration charging or air-conditioning troubleshooting.

What Is Included in This CMC-C Practice Test?

This product contains 750 practice questions and answers covering the technical subject matter relevant to Tennessee CMC-C preparation. The questions include practical troubleshooting, calculations, equipment operation, installation concepts, safety situations, and scenario-based HVAC and refrigeration problems.

You will find practice covering areas such as:

• HVAC heating and cooling principles
• Furnaces, heat pumps, boilers, and cooling equipment
• Refrigeration systems and refrigerant circuits
• TXVs, fixed metering devices, EEVs, receivers, accumulators, EPRs, and related controls
• Refrigerant charging, evacuation, recovery, restrictions, and oil management
• Gas pressure, regulators, burners, combustion air, venting, and combustion troubleshooting
• Hydronic piping, pumps, valves, balancing, expansion tanks, and steam systems
• Electrical measurements, motors, controls, transformers, contactors, and voltage problems
• HVAC controls, sensors, VFDs, economizers, and variable-air-volume systems
• Duct sizing, static pressure, airflow, ventilation, exhaust, and air balancing
• Sensible-heat and HVAC load calculations
• Fire and smoke protection concepts
• OSHA-oriented jobsite and equipment safety
• Commissioning and troubleshooting situations

The material is intended as a practice resource, not as a substitute for the official Tennessee examination bulletin, licensing requirements, or permitted examination references.

How We Created This Tennessee CMC-C Practice Test

The question set was developed around the official CMC-C subject areas and the practical knowledge reflected in the examination scope. The questions emphasize situations an HVAC/refrigeration contractor may encounter when diagnosing, installing, commissioning, or servicing equipment.

The practice material focuses on:

• Official CMC-C subject areas
• HVAC and refrigeration operating principles
• Fuel-gas and combustion concepts
• Mechanical and refrigerant piping
• Electrical and control troubleshooting
• Air distribution and ventilation
• Load calculations and practical mathematics
• Safety and equipment-protection situations
• Original scenarios with explanations rather than copied examination questions

The official Prov bulletin states that the examination is designed around knowledge qualified individuals would normally encounter during regular work operations and recommends becoming familiar with both the subject areas and permitted reference materials.

Who Can Take the Tennessee CMC-C HVAC Contractor Exam?

The CMC-C trade examination applies to candidates seeking the Tennessee HVAC/Refrigeration Contractor classification. Tennessee’s classification outline identifies CMC-C as a trade-exam-required classification covering HVAC, refrigeration, and gas piping.

Important licensing points include:

• Tennessee contractor licensing requirements are determined by the Tennessee Board for Licensing Contractors.
• New contractor applicants must take the Tennessee Business & Law examination along with a required trade examination.
• CMC-C requires its applicable trade examination.
• The current Prov bulletin specifically identifies CMC and CMC-A as the examinations requiring Board pre-approval before scheduling; CMC-C is not listed among those two examinations.
• Passing the trade examination alone does not automatically issue a contractor license; the Board separately reviews the licensing application and applicable qualifications.
• For projects of $25,000 or more, Tennessee generally requires the appropriate contractor license, including HVAC/mechanical subcontracting situations covered by the state’s licensing rules.

Because licensing circumstances can depend on the applicant and project, candidates should confirm their individual eligibility directly with the Tennessee Board before registering.

How to Register for the Tennessee CMC-C Exam

For current testing, Prov administers Tennessee contractor examinations. Candidates can register through Prov’s scheduling system or contact Prov directly. The current bulletin states that CMC-C candidates follow the standard Prov registration process, while the full CMC and CMC-A examinations have separate Board-approval requirements.

The current process includes:

• Select the Tennessee Board for Licensing Contractors as the certifying body
• Select the appropriate license/examination
• Enter the requested candidate information
• Select an available testing date, time, and location
• Complete payment to secure the appointment
• Review the testing instructions and permitted references before test day

Prov currently lists a $53 examination fee per attempt. Appointments can be taken at Prov testing centers or through the Examroom remote-proctoring option.

Candidates should verify the current scheduling information before registering because testing procedures and provider information can change.

How Is the Tennessee CMC-C Exam Scored?

The current Prov bulletin states that Tennessee contractor examinations use a 73% passing standard. With a 100-question CMC-C examination, a candidate needs a score of at least 73% to receive a passing result.

The important points are:

• 100 questions
• 73% passing standard
• 2-hour testing period
• Results are scored after completion
• Candidates who do not pass receive diagnostic information identifying content areas needing improvement
• Passing the examination is only one part of the Tennessee contractor licensing process

A useful preparation target is to consistently perform above the minimum passing level on practice sessions rather than studying only to reach the exact cutoff.

What References Can You Use for the CMC-C Exam?

The Tennessee CMC-C examination is open book. The current Prov bulletin identifies reference materials including the International Mechanical Code 2018, Modern Refrigeration and Air Conditioning, 21st Edition, Refrigeration and Air Conditioning Technology, 9th Edition, the Residential Comfort System Installation Standards Manual, 8th Edition, and OSHA 29 CFR 1926.

The bulletin also provides specific rules for preparing permitted references. Highlighting and permanent tabs are allowed, while handwritten notes, movable tabs, Post-it notes, photocopied documents, and practice examinations are not permitted inside reference books under the stated testing rules.

Through January 1, 2027, the bulletin also permits specified PSI-approved alternate references for candidates who already own materials from the prior testing vendor.

How to Study for the Tennessee CMC-C HVAC Exam

A strong preparation plan should combine technical review with timed practice. Because the examination is open book, learning how to locate information efficiently is also part of preparation.

• Start with the official CMC-C subject-area distribution.
• Give extra study time to Air Distribution and Venting and Piping because they represent large portions of the current outline.
• Review fuel-gas and combustion problems carefully.
• Practice refrigeration diagnosis using pressure, temperature, superheat, and subcooling together.
• Work through HVAC load and sensible-heat calculations without relying on memorized answers.
• Review electrical measurements such as voltage, current, resistance, motor loading, and control circuits.
• Practice finding information quickly in permitted reference books.
• Mark important reference locations with permitted permanent tabs before exam day.
• Keep a record of missed practice questions and revisit the underlying concept rather than memorizing the answer.

The official bulletin specifically recommends becoming familiar with the examination subject areas and reference materials before entering the testing room.

Tennessee CMC-C Exam Day Tips

Prov’s current testing instructions require candidates to arrive with appropriate identification and permitted reference materials. Testing centers require a valid government-issued photo ID, and the name must correspond with the registration information.

Keep these points in mind:

• Arrive early enough to complete check-in.
• Bring a valid government-issued photo ID.
• Bring only permitted reference materials.
• Use only an approved simple four-function calculator if you bring one.
• Do not bring cell phones, smart watches, cameras, recording devices, or other prohibited electronic devices into the testing room.
• Remember that the examination timer continues during an authorized break.
• Review and finalize questions before taking a break because previously displayed questions may be frozen after the break.
• Become familiar with your reference books before test day rather than learning their organization inside the testing room.

Common Tennessee CMC-C Preparation Mistakes to Avoid

Many candidates lose valuable preparation time by studying only the topics they already understand. CMC-C covers a broad mechanical skill set, so a balanced review is more useful.

Avoid:

• Studying only refrigeration and ignoring air distribution
• Memorizing answer choices without understanding the HVAC principle
• Ignoring fuel-gas and combustion questions
• Avoiding calculations because they represent a smaller portion of the outline
• Failing to review piping and hydronic systems
• Practicing without timing yourself
• Waiting until exam week to organize permitted reference books
• Assuming an open-book exam requires little preparation
• Changing an answer simply because another option sounds more technical
• Ignoring the wording of scenario-based questions
• Treating a practice question as evidence that the same question will appear on the actual examination

The current exam has only two hours for 100 questions, so spending excessive time searching for individual answers can become a serious time-management problem.

Is the Tennessee CMC-C Exam Difficult?

The difficulty depends heavily on your field experience, familiarity with the reference material, and ability to work through technical questions efficiently. The exam covers a wide range of HVAC/refrigeration subjects rather than one narrow specialty.

Candidates who prepare only by memorizing definitions may find the practical scenarios more challenging. A better approach is to understand the relationship between airflow, temperature, pressure, electrical readings, refrigerant behavior, combustion, piping, and controls.

How to Pass the Tennessee CMC-C HVAC/Refrigeration Exam

Use the practice material as a diagnostic tool, not simply as a question bank. Work until you can explain the reasoning behind your answers and locate supporting information efficiently in your permitted references.

A practical preparation sequence is to review the official CMC-C subject areas, complete topic-based practice, analyze missed questions, strengthen weak technical areas, then take timed mixed-question sessions. Aim to perform consistently above the 73% passing standard during practice so that you have a reasonable margin for difficult questions on exam day. The practice material cannot guarantee a passing result, but disciplined review can make your preparation more structured and targeted.

Start Preparing for Exam

Use the practice questions to identify the subjects that need the most attention, then return to the appropriate technical references and repeat the difficult areas until the reasoning becomes familiar. With coverage spanning refrigeration, HVAC equipment, piping, fuel gas, controls, electrical concepts, load calculations, ventilation, air distribution, and safety, the material is designed to support structured preparation for the Tennessee CMC-C trade examination.

Sample Questions and Answers

Question 1. A commercial split-system air conditioner is operating continuously on a hot afternoon. The evaporator coil is clean, the indoor blower is operating at the manufacturer’s specified airflow, and the return-air temperature is 78°F while the supply-air temperature is 61°F. The measured suction pressure is substantially lower than the manufacturer’s expected operating range, and the superheat is high. Which condition is MOST likely responsible?

A. Excessive refrigerant charge
B. Restricted airflow across the evaporator
C. Refrigerant undercharge
D. Oversized condenser coil

Correct Answer: C

Answer Explanation: Option C is correct because a low suction pressure combined with high superheat is a classic indication that the evaporator is being starved of refrigerant. With adequate airflow and a clean coil already established, a refrigerant undercharge becomes the strongest diagnosis. Insufficient refrigerant reduces the amount of liquid entering the metering device and evaporator, causing less refrigerant to boil and absorb heat. The remaining vapor becomes highly superheated before reaching the compressor. An accurate diagnosis should be confirmed with the manufacturer’s charging procedure, leak inspection, and appropriate pressure and temperature measurements rather than adding refrigerant based only on suction pressure.

Why the other options are incorrect:

Option A would normally tend toward higher suction pressure and lower superheat under comparable conditions.

Option B is contradicted by the established adequate blower operation and clean evaporator.

Option D does not explain the combination of low suction pressure and high superheat.

Study Guide:
Review the relationship between suction pressure, superheat, and evaporator feeding.
Know how undercharge, overcharge, airflow problems, and restrictions produce different symptoms.
Always diagnose refrigerant charge using manufacturer-required measurements and procedures.
For troubleshooting questions, evaluate the complete symptom pattern rather than relying on one gauge reading.

Question 2. During startup of a gas-fired rooftop heating unit, the inducer motor starts and the ignition sequence begins. The ignitor operates, but the gas valve does not open because the pressure switch remains open. The vent connector is unobstructed, but the technician discovers that the combustion-air intake is partially blocked. What is the BEST corrective action?

A. Remove the pressure switch and jumper its terminals
B. Correct the combustion-air restriction and verify the pressure-switch circuit
C. Increase the gas-valve outlet pressure
D. Replace the ignitor

Correct Answer: B

Answer Explanation: Option B is correct because the pressure switch is a safety device intended to verify an acceptable draft or pressure condition before the burner sequence proceeds. A restricted combustion-air intake can prevent the inducer from establishing the pressure required to close the switch. Correcting the obstruction and then verifying the pressure-switch circuit restores the intended safety sequence. The technician should also determine why the intake became restricted and confirm that the unit operates according to the manufacturer’s specifications. Safety controls should never be bypassed simply to force ignition. Proper combustion air, venting, draft, and safety-control operation are essential to prevent unsafe combustion products from entering occupied areas.

Why the other options are incorrect:

Option A defeats a safety control and can create a dangerous operating condition.

Option C changes fuel pressure without addressing the actual combustion-air problem.

Option D is inappropriate because the ignitor is already operating.

Study Guide:
Understand the purpose of inducer motors and pressure switches in gas-fired equipment.
Review combustion-air requirements and common causes of inadequate draft.
Never permanently bypass a furnace safety control to obtain operation.
Diagnose the complete ignition sequence before replacing components.

Question 3. A hydronic air-handling unit has a heating coil supplied by a hot-water loop. The entering-water temperature is normal, but the leaving-water temperature is nearly identical to the entering-water temperature even when the control valve is commanded fully open. The circulation pump is running and the strainer is clean. Which condition should the technician investigate FIRST?

A. Insufficient water flow through the heating coil
B. Excessive refrigerant charge
C. Incorrect compressor rotation
D. Excessive condenser airflow

Correct Answer: A

Answer Explanation: Option A is correct because a very small temperature change across a heating coil can indicate that insufficient water is moving through the coil to transfer the expected amount of heat. Even though the pump is operating, actual flow may still be inadequate because of a closed isolation valve, air trapped in the coil, pump performance problems, incorrect balancing, a control-valve issue, or another hydronic restriction. The technician should verify differential pressure and actual flow conditions rather than assuming that a running pump guarantees adequate circulation. In hydronic systems, heat transfer depends on both water temperature and mass flow. A diagnosis should therefore evaluate the entire water circuit from the pump through the coil and back to the source.

Why the other options are incorrect:

Option B concerns refrigeration and does not explain poor heat transfer in the hot-water coil.

Option C applies to compressor operation, not hydronic circulation.

Option D affects condenser performance and is unrelated to this heating-coil symptom.

Study Guide:
Review hydronic heating principles and temperature difference across coils.
Remember that a running pump does not automatically prove adequate water flow.
Study balancing valves, strainers, air elimination, pumps, and control valves.
Use differential pressure and flow information when diagnosing hydronic performance.

Question 4. A rooftop package unit repeatedly trips its motor overload after operating for approximately 20 minutes. Voltage at the motor terminals is within the manufacturer’s acceptable range, the shaft turns freely when power is removed, and the motor nameplate amperage is 12.0 A. During operation, the motor draws 15.5 A. The most appropriate next step is to:

A. Increase the motor overload setting above the nameplate rating
B. Add refrigerant to reduce compressor loading
C. Determine why the motor is operating above its rated load
D. Replace the thermostat

Correct Answer: C

Answer Explanation: Option C is correct because a motor consistently drawing substantially more current than its nameplate rating indicates an abnormal operating condition that must be identified before changing the overload protection. Possible causes include excessive mechanical load, incorrect blower adjustment, excessive static pressure, bearing problems that appear only when hot, incorrect motor configuration, or an equipment condition causing the motor to work beyond its design load. Increasing the overload setting simply defeats the protection intended to prevent motor overheating and damage. The technician should compare operating conditions with manufacturer specifications, verify motor wiring and configuration, measure system static pressure where applicable, and determine whether the mechanical load is appropriate.

Why the other options are incorrect:

Option A can allow the motor to overheat and may create a fire or equipment hazard.

Option B is unrelated to the blower motor’s excessive current unless a specific compressor-loading relationship has been established.

Option D does not address an excessive motor-current condition.

Study Guide:
Know how motor nameplate data is used during HVAC troubleshooting.
Review overload protection and why protective devices should not be arbitrarily upsized.
Understand static pressure and mechanical loading effects on blower motors.
Compare measured amperage with manufacturer specifications before replacing components.

Question 5. A newly installed commercial air-conditioning system has insufficient cooling in several zones. The technician performs a load calculation and discovers that the installed cooling equipment is significantly larger than the calculated design load. The building also has short operating cycles and elevated indoor humidity. Which consequence is MOST likely associated with the oversized cooling equipment?

A. Excessive compressor superheat caused solely by oversizing
B. Improved dehumidification because the system runs for shorter periods
C. Longer compressor operating cycles and lower indoor humidity
D. Reduced latent moisture removal because the system cycles off before adequate dehumidification occurs

Correct Answer: D

Answer Explanation: Option D is correct because oversized cooling equipment can satisfy the sensible temperature load quickly and shut off before the evaporator has operated long enough to remove sufficient latent moisture from the space. The result can be acceptable or even low dry-bulb temperature while indoor relative humidity remains unnecessarily high. Proper equipment selection begins with an accurate load calculation rather than simply choosing a larger capacity for additional margin. Oversizing can also contribute to short cycling, reduced comfort, increased equipment cycling, and inefficient operation. A contractor should evaluate both sensible and latent loads and select equipment whose capacity and controls are appropriate for the actual design conditions.

Why the other options are incorrect:

Option A is not an automatic consequence of equipment oversizing.

Option B reverses the typical humidity-control effect of short cycling.

Option C is opposite to what oversizing commonly causes.

Study Guide:
Review sensible and latent cooling loads and their relationship to equipment selection.
Understand why Manual J or applicable load-calculation procedures matter.
Know the comfort and efficiency consequences of oversized equipment.
Avoid selecting equipment based solely on floor area or a large capacity margin.

Question 6. A technician finds frost forming on the suction line immediately downstream of the evaporator. The customer reports weak cooling. The evaporator filter is clean, the blower is operating correctly, and the measured superheat is very low. Which condition is MOST consistent with these findings?

A. Excessive refrigerant feeding into the evaporator
B. Severe refrigerant undercharge
C. Excessive duct leakage on the supply side
D. Insufficient refrigerant entering the evaporator

Correct Answer: A

Answer Explanation: Option A is correct because very low superheat indicates that refrigerant is leaving the evaporator with relatively little sensible heat added after boiling. If liquid refrigerant continues beyond the intended evaporator outlet, the suction line can become excessively cold and frost may develop. Possible causes include an improperly adjusted or malfunctioning metering device, excessive refrigerant feed, or another control problem that allows the evaporator to become overfed. This must be distinguished from an undercharge, which typically produces high superheat because the evaporator becomes starved. The technician should verify airflow, operating pressures, superheat or subcooling as appropriate to the system, metering-device operation, and manufacturer specifications before making a charge adjustment.

Why the other options are incorrect:

Option B generally produces high rather than very low superheat.

Option C can affect system performance but does not directly explain very low evaporator superheat.

Option D would starve the evaporator and normally increase superheat.

Study Guide:
Study the difference between evaporator starvation and overfeeding.
Know how superheat helps determine whether refrigerant is fully vaporized at the evaporator outlet.
Review metering devices and their role in controlling refrigerant flow.
Do not diagnose charge problems from frost alone.

Question 7. A commercial kitchen exhaust system is being evaluated after a complaint that smoke and cooking odors are entering the dining area. The exhaust fan is operating, but the measured airflow is substantially below the design requirement. The filters are clean and the fan rotation is correct. Which condition should be investigated next?

A. Refrigerant superheat
B. Duct system pressure loss and restrictions
C. Compressor crankcase heater operation
D. Heating-water temperature

Correct Answer: B

Answer Explanation: Option B is correct because inadequate exhaust airflow despite a properly operating fan can result from excessive system resistance. The technician should inspect the ductwork for restrictions, collapsed sections, excessive fittings, improperly sized components, dirty grilles or hoods, dampers that are not fully open, and other conditions that increase static pressure. The actual fan performance should then be compared with the design operating point. Kitchen exhaust systems are particularly dependent on proper airflow and makeup-air relationships because inadequate exhaust can allow contaminants and odors to migrate into occupied spaces. The investigation should therefore consider both the exhaust path and the building’s overall air balance.

Why the other options are incorrect:

Option A applies to refrigeration-system performance rather than kitchen exhaust airflow.

Option C does not determine exhaust fan airflow.

Option D concerns hydronic heating and is unrelated to the exhaust-air deficiency.

Study Guide:
Review duct static pressure, fan curves, and system resistance.
Understand how elbows, transitions, dampers, and restrictions affect airflow.
Study commercial exhaust and makeup-air principles.
Remember that airflow performance must be evaluated against the system’s design requirements.

Question 8. During installation of a refrigerant piping system, the contractor plans to route a long suction line with several vertical rises. Which design consideration is MOST important for maintaining reliable compressor operation?

A. Eliminating all horizontal piping regardless of system design
B. Increasing the suction-line diameter as much as possible without calculation
C. Maintaining proper refrigerant velocity and oil return while controlling pressure drop
D. Using the smallest available pipe to increase refrigerant velocity in every situation

Correct Answer: C

Answer Explanation: Option C is correct because refrigerant piping must be designed to balance pressure drop, refrigerant velocity, and reliable oil return. A suction line that is excessively large may permit refrigerant velocity to fall too low for dependable oil movement under certain operating conditions, while an undersized line can create excessive pressure drop and reduce system capacity. Vertical risers require particular attention because oil must be carried back to the compressor against gravity. Proper pipe sizing therefore depends on refrigerant type, capacity, line length, vertical lift, operating conditions, and manufacturer or design guidance. Long piping systems should not be sized simply by choosing the largest or smallest pipe available.

Why the other options are incorrect:

Option A ignores legitimate piping configurations required by system layout.

Option B can cause poor oil return and unnecessary material cost.

Option D can create excessive pressure drop and unacceptable system performance.

Study Guide:
Review suction, liquid, and discharge-line design principles.
Understand the relationship between pipe diameter, velocity, oil return, and pressure drop.
Pay special attention to vertical risers and long piping runs.
Use recognized piping tables and manufacturer data rather than guesswork.

Question 9. A technician is servicing a gas-fired furnace in a mechanical room. The furnace has experienced repeated rollout incidents. Inspection reveals that the vent connector is partially obstructed and combustion air is also inadequate. What is the technician’s FIRST priority?

A. Increase the gas input rate to stabilize the flame
B. Replace the thermostat
C. Bypass the rollout switch
D. Correct the unsafe venting and combustion-air conditions before returning the furnace to service

Correct Answer: D

Answer Explanation: Option D is correct because repeated rollout is a serious combustion and safety problem. An obstructed vent and inadequate combustion air can disrupt proper combustion, draft, and the movement of combustion products. The rollout switch is a protective device and should never be bypassed merely to restore operation. The technician must identify and correct the underlying hazardous conditions, verify the venting system and combustion-air provisions, inspect the burner and heat exchanger as appropriate, and confirm safe operation before placing the furnace back into service. Gas-fired equipment requires particular attention to combustion products because improper venting can expose occupants to carbon monoxide and other hazards.

Why the other options are incorrect:

Option A could worsen combustion and create additional hazards.

Option B has no meaningful relationship to the venting deficiency.

Option C defeats a critical safety device and is unacceptable.

Study Guide:
Review combustion-air, venting, draft, and rollout safety principles.
Understand why rollout switches and other safety controls must remain functional.
Know the hazards associated with blocked vents and improper combustion.
Treat repeated safety-control trips as evidence of an underlying fault, not as a nuisance.

Question 10. A packaged rooftop unit uses a belt-driven supply fan. After several months of operation, the belt repeatedly fails even though the belt size is correct. Inspection shows that the motor and fan pulleys are not aligned and the belt is visibly running at an angle. What is the BEST corrective action?

A. Correct pulley alignment and verify belt tension according to manufacturer requirements
B. Increase the belt tension substantially above the manufacturer’s specification
C. Install a larger motor regardless of the measured load
D. Reduce the supply-air temperature setpoint

Correct Answer: A

Answer Explanation: Option A is correct because misaligned pulleys impose abnormal lateral forces on the belt and can cause rapid wear, overheating, noise, vibration, and premature failure. Correcting the alignment and then setting belt tension according to the equipment manufacturer’s requirements addresses both the mechanical cause and proper operating condition. Excessive belt tension can overload bearings and shorten their service life, while insufficient tension can cause slipping. A larger motor does not correct a mechanical alignment problem and could introduce other design issues. Proper fan maintenance should include inspection of bearings, sheaves, belts, guards, alignment, tension, and operating conditions.

Why the other options are incorrect:

Option B may create excessive bearing loads and does not correct pulley misalignment.

Option C does not address the actual mechanical defect.

Option D changes a control setting without addressing belt failure.

Study Guide:
Study belt-driven fan maintenance and pulley alignment.
Know the effects of excessive and insufficient belt tension.
Understand why mechanical alignment affects bearing and belt life.
Use manufacturer procedures for belt installation and tension adjustment.

Question 11. A building owner reports that several rooms are warmer than the rest of the building even though the central air-handling unit is operating normally. Supply-air temperature is satisfactory at the air handler, but airflow at the affected diffusers is much lower than expected. Inspection reveals several disconnected flexible-duct sections above the ceiling. What is the MOST likely effect of these disconnected sections?

A. Increased refrigerant subcooling
B. Reduced delivered airflow and increased energy loss
C. Increased compressor oil pressure
D. Lower gas-line pressure

Correct Answer: B

Answer Explanation: Option B is correct because disconnected flexible ducts allow conditioned air to escape into the ceiling or building cavity rather than reaching the intended occupied spaces. This reduces the amount of supply air delivered to the affected rooms and can produce comfort complaints even though the central equipment is producing air at the proper temperature. Duct leakage can also increase fan energy requirements and reduce overall system efficiency. Flexible duct should be properly supported, connected, sealed, and installed without excessive compression or sharp bends. The technician should inspect the entire distribution system, measure airflow where appropriate, and correct leakage and installation deficiencies before attempting to alter the equipment capacity.

Why the other options are incorrect:

Option A concerns refrigerant-system operation and is unrelated to disconnected ductwork.

Option C is not a direct consequence of supply-duct leakage.

Option D concerns the fuel system and does not explain the airflow deficiency.

Study Guide:
Review duct leakage, airflow distribution, and flexible-duct installation.
Understand why supply-air temperature alone cannot prove adequate room cooling.
Study the relationship between duct resistance, leakage, and fan performance.
Verify delivered airflow at the occupied zones when diagnosing comfort complaints.

Question 12. A technician is calculating the required cooling capacity for a new commercial space. The owner states that the previous contractor used a simple rule of thumb based only on floor area. The technician finds large south-facing windows, significant internal equipment loads, occupancy that varies throughout the day, and substantial ventilation requirements. What is the MOST appropriate approach?

A. Select equipment based solely on square footage
B. Add 50% capacity to the largest available unit for safety
C. Perform a proper heating and cooling load calculation using the relevant design conditions
D. Select the same equipment capacity used in the previous building

Correct Answer: C

Answer Explanation: Option C is correct because HVAC equipment should be selected from a calculated design load rather than a generalized square-footage rule. Cooling demand can be strongly affected by solar gain, building envelope characteristics, occupancy, lighting, equipment, ventilation, infiltration, orientation, and operating schedules. Oversizing does not automatically provide better performance and can create short cycling and humidity-control problems. A proper load calculation establishes the sensible and latent requirements under defined design conditions and provides a rational basis for equipment selection and distribution-system design. The Tennessee CMC-C examination outline specifically includes load calculation as a tested subject area, making practical application of load-calculation principles important for exam preparation.

Why the other options are incorrect:

Option A ignores major variables that influence actual cooling demand.

Option B creates arbitrary oversizing rather than engineering-based capacity selection.

Option D assumes another building has identical load characteristics.

Study Guide:
Review Manual J and Manual N load-calculation concepts applicable to the project.
Study solar, internal, ventilation, infiltration, sensible, and latent loads.
Understand why equipment capacity should follow calculated demand.
Know how oversizing affects cycling, humidity control, comfort, and efficiency.

Question 13. A refrigeration system has a liquid receiver installed in the liquid line. During operation, the technician observes unstable liquid supply to the metering device. The receiver outlet is partially restricted by a malfunctioning service valve. Which consequence is MOST likely?

A. Reduced liquid flow to the metering device and possible evaporator starvation
B. Increased evaporator airflow
C. Increased combustion-air supply
D. Lower building infiltration

Correct Answer: A

Answer Explanation: Option A is correct because a restriction downstream of the receiver can limit the flow of liquid refrigerant available to the metering device. If the metering device does not receive a stable supply of liquid, the evaporator can become starved, reducing cooling capacity and potentially producing high superheat. The technician should verify the valve position and temperature or pressure conditions across the suspected restriction while following safe service procedures. Refrigeration restrictions must be distinguished from low charge because both can produce low evaporator feeding, but the pressure and temperature pattern across the system can help identify the actual cause. A liquid receiver is intended to store and manage liquid refrigerant within the system, not compensate for an unintended flow restriction.

Why the other options are incorrect:

Option B concerns air-side operation and does not result directly from a liquid-line restriction.

Option C applies to combustion systems rather than refrigerant circulation.

Option D concerns building-envelope airflow and is unrelated to the refrigeration restriction.

Study Guide:
Review liquid receivers, liquid lines, metering devices, and evaporator feeding.
Learn how restrictions differ diagnostically from low refrigerant charge.
Study pressure and temperature changes across suspected restrictions.
Always verify valve position and system configuration before condemning a component.

Question 14. A commercial air-conditioning unit is operating normally at first, but after several hours the compressor trips on thermal overload. The condenser coil is heavily fouled, outdoor airflow is restricted, and the discharge pressure is elevated. Which condition is the MOST likely primary cause?

A. Excessive indoor airflow
B. Excessive condenser heat rejection caused by restricted airflow
C. Low evaporator entering-air temperature
D. Excessive return-air filtration efficiency

Correct Answer: B

Answer Explanation: Option B is correct because a heavily fouled condenser and restricted outdoor airflow prevent the condenser from rejecting heat efficiently. As condensing temperature and pressure rise, compressor compression work increases, which can raise compressor motor temperature and eventually cause thermal overload. The correct response is to restore the condenser’s required airflow and heat-transfer capability, then verify operating pressures, temperatures, amperage, and system performance under appropriate conditions. Simply resetting the overload does not correct the underlying cause. The technician should also determine why the condenser became fouled and whether other airflow restrictions exist. Proper condenser maintenance is therefore directly related to compressor reliability and system efficiency.

Why the other options are incorrect:

Option A does not explain the documented high condensing pressure and fouled condenser.

Option C is not the primary cause of the elevated outdoor-side heat-rejection problem.

Option D does not directly produce high condenser pressure.

Study Guide:
Review condenser heat rejection and the effect of outdoor airflow.
Understand how high condensing pressure increases compressor workload.
Study the relationship among condenser fouling, head pressure, amperage, and compressor temperature.
Always correct the heat-transfer or airflow problem before repeatedly resetting overload protection.

Question 15. A contractor is installing a new gas-fired HVAC system in a commercial mechanical room. The equipment manufacturer specifies combustion-air openings based on the installation conditions. The contractor proposes reducing the opening size because the room already feels well ventilated to personnel. What is the BEST response?

A. Reduce the openings because natural room ventilation is sufficient
B. Seal the openings after commissioning to improve energy efficiency
C. Size and install combustion-air provisions according to applicable requirements and the equipment manufacturer’s instructions
D. Replace the gas appliance with a larger unit

Correct Answer: C

Answer Explanation: Option C is correct because combustion-air requirements are determined by the equipment, installation configuration, applicable code requirements, and manufacturer’s instructions—not by whether the room subjectively feels ventilated. Gas-fired appliances require sufficient air for safe combustion and proper operation. Inadequate combustion air can contribute to incomplete combustion, unstable flames, improper draft, rollout, carbon-monoxide production, and unsafe venting conditions. The contractor must evaluate the installation conditions and provide combustion-air openings or other approved provisions as required. Energy-efficiency concerns do not justify reducing required combustion air. Any modification to the installation should be evaluated against the applicable code provisions and equipment instructions before the appliance is placed into service.

Why the other options are incorrect:

Option A relies on human comfort rather than combustion requirements.

Option B can create an unsafe appliance installation by eliminating required air.

Option D changes equipment capacity without addressing the combustion-air requirement.

Study Guide:
Review combustion-air requirements for gas-fired appliances.
Understand the difference between human ventilation comfort and combustion-air requirements.
Study how inadequate combustion air can affect flame stability, draft, and carbon-monoxide risk.
Use the applicable code provisions and manufacturer’s installation instructions when determining required openings.