Ohio HVAC Contractor Practice Test

Free Ohio HVAC Contractor Practice Sample Questions & Answers

Question 1. A split air-conditioning system is operating with a normal indoor airflow rate, but the evaporator coil is beginning to ice over. The measured suction pressure is lower than expected, while the liquid line is warmer than normal. Which condition should the technician investigate first?

A. Excessive condenser airflow

B. Low refrigerant charge

C. Oversized evaporator coil

D. Excessive liquid-line subcooling

Correct Answer. B. Low refrigerant charge

Explanation:

A low refrigerant charge can reduce the amount of refrigerant entering the evaporator, causing the coil to operate at an abnormally low saturation temperature. This can lead to coil icing and reduced cooling capacity. A technician should verify operating pressures, superheat, subcooling, and the manufacturer’s charging procedure before adding refrigerant. Airflow should still be confirmed because restricted airflow can also cause icing, but the question establishes normal indoor airflow. The combination of low suction pressure and abnormal liquid-line conditions points toward a refrigeration-side problem. The system should also be inspected for leaks before correcting the refrigerant charge.

Question 2. A gas-fired forced-air furnace starts normally, but the burner shuts off shortly after ignition while the blower continues operating. The flame sensor is clean and properly positioned. Which component should be checked next?

A. Limit control circuit

B. Condenser fan motor

C. Evaporator metering device

D. Compressor overload

Correct Answer. A. Limit control circuit

Explanation:

If the burners ignite and then shut down while the blower continues operating, the furnace control sequence should be evaluated. A limit control or related safety circuit can interrupt burner operation when an unsafe temperature condition is detected. The technician should verify whether the limit switch is opening, then investigate the underlying cause rather than bypassing the safety device. Excessive temperature can result from restricted airflow, a dirty filter, blocked ductwork, incorrect blower operation, or other conditions. A clean flame sensor makes flame-proving failure less likely, while the condenser and compressor components are unrelated to the furnace’s burner sequence.

Question 3. A heat pump operates in heating mode, but the indoor air temperature remains below the expected supply temperature during mild outdoor conditions. The outdoor coil is clean and the indoor airflow is within the manufacturer’s specified range. Which measurement would provide the most useful information when evaluating the refrigeration circuit?

A. Compressor crankcase heater resistance only

B. Refrigerant superheat and subcooling

C. Indoor blower motor horsepower only

D. Thermostat display temperature only

Correct Answer. B. Refrigerant superheat and subcooling

Explanation:

Superheat and subcooling measurements provide valuable information about refrigerant conditions at different points in the system. When a heat pump is not delivering expected heating performance, these measurements can help determine whether the system has an incorrect refrigerant charge or another refrigeration problem. The technician should compare measured values with the manufacturer’s specifications and consider outdoor temperature and operating mode before making adjustments. A single pressure reading is usually insufficient for diagnosing the complete refrigerant circuit. Because airflow has already been confirmed as acceptable and the outdoor coil is clean, evaluating refrigerant behavior is an appropriate next diagnostic step.

Question 4. An air-conditioning compressor has the correct supply voltage at the disconnect, but the compressor does not start when there is a cooling demand. Voltage is absent at the compressor terminals. Which component should be tested before condemning the compressor?

A. Evaporator coil

B. Contactor and control circuit

C. Condenser coil

D. Refrigerant filter

Correct Answer. B. Contactor and control circuit

Explanation:

The absence of voltage at the compressor terminals does not establish that the compressor has failed. The technician should trace the electrical circuit to determine where power is being interrupted. The contactor, thermostat signal, low-voltage wiring, control board, safety controls, and associated components should be checked according to the equipment’s wiring diagram. If the contactor is not closing, the control circuit should be investigated before testing the compressor as the primary fault. This approach prevents unnecessary compressor replacement and helps identify whether a low-voltage control problem or an open safety device is preventing the compressor from receiving operating voltage.

Question 5. A commercial HVAC system has several air-handling zones. One zone consistently receives more supply air than the design calls for, while another zone receives too little. The fans and filters are operating correctly. Which adjustment is most appropriate?

A. Increase refrigerant charge

B. Adjust the branch balancing dampers

C. Increase compressor voltage

D. Lower the furnace gas pressure

Correct Answer. B. Adjust the branch balancing dampers

Explanation:

Air balancing is used to distribute conditioned air according to the requirements of individual zones or branches. If one branch receives excessive airflow while another is starved, the balancing dampers can be adjusted to redistribute airflow. The technician should use measured airflow values and compare them with the system design or commissioning requirements rather than making arbitrary adjustments. Increasing refrigerant charge, changing compressor voltage, or altering furnace gas pressure would not directly correct an air-distribution imbalance. Proper balancing improves comfort and system performance while helping ensure that each occupied area receives the amount of conditioned air intended by the system design.

Question 6. During installation of a new rooftop HVAC unit, the contractor discovers that the manufacturer’s required service clearances cannot be maintained because of an adjacent structural obstruction. What should the contractor do?

A. Install the equipment anyway because the unit will still operate

B. Reduce the clearances after increasing refrigerant charge

C. Resolve the installation conflict before proceeding

D. Remove the equipment access panels permanently

Correct Answer. C. Resolve the installation conflict before proceeding

Explanation:

Required equipment clearances are important for safe installation, service access, ventilation, and proper equipment operation. If an obstruction prevents the required clearance from being maintained, the contractor should resolve the conflict before completing the installation. Depending on the project, this may involve relocating the equipment, modifying the obstruction, or obtaining an approved installation solution consistent with the manufacturer’s requirements and applicable codes. Simply installing the unit in an unsuitable location can create maintenance problems and may violate installation requirements. Service panels should remain accessible, and operating adjustments such as refrigerant charge cannot compensate for inadequate physical clearance around equipment.

Question 7. A refrigeration system has normal condenser airflow but shows higher-than-expected condensing pressure and a temperature difference across the condenser that is greater than the manufacturer’s expected range. Which condition should be investigated?

A. Excessive heat rejection or refrigerant-side restriction

B. Low indoor humidity only

C. Undersized thermostat wire

D. Excessive evaporator airflow

Correct Answer. A. Excessive heat rejection or refrigerant-side restriction

Explanation:

Elevated condensing pressure indicates that the refrigeration system is having difficulty rejecting heat or that refrigerant flow through the condenser circuit may be restricted. The technician should verify condenser cleanliness, entering-air temperature, airflow, refrigerant charge, and the condition of components that could restrict refrigerant movement. A high condensing temperature difference should be evaluated against the equipment manufacturer’s specifications rather than interpreted from pressure alone. Electrical control wiring and indoor airflow may affect overall system operation but do not directly explain an abnormal condenser condition in this situation. Accurate pressure and temperature measurements are important before deciding which component requires correction.

Question 8. A hydronic heating loop has adequate boiler temperature, but several terminal units remain underheated. The circulator is operating, and the system pressure is within the expected range. Which measurement would best help determine whether the circuit is receiving sufficient water flow?

A. Voltage at the thermostat only

B. Flow rate through the hydronic circuit

C. Gas pressure at an unrelated appliance

D. Outdoor humidity level

Correct Answer. B. Flow rate through the hydronic circuit

Explanation:

Adequate boiler temperature does not guarantee that enough heated water is reaching the terminal units. Measuring actual flow through the affected circuit helps determine whether the hydronic system is delivering the required quantity of water. Low flow can result from an improperly adjusted balancing valve, blocked strainer, trapped air, incorrect circulator selection, closed valve, or excessive system resistance. The technician should compare measured flow with the design requirement and investigate any significant difference. Checking thermostat voltage or unrelated equipment conditions would not directly establish whether the hydronic circuit is receiving adequate water for proper heat transfer.

Question 9. A technician is servicing an HVAC system that uses a motor with a capacitor specified by the equipment manufacturer. The replacement capacitor has the correct voltage rating but a different capacitance value. What is the best practice?

A. Install it because the voltage rating matches

B. Install it only if the motor runs quietly

C. Use the manufacturer’s specified capacitance value

D. Increase the capacitance to improve motor speed

Correct Answer. C. Use the manufacturer’s specified capacitance value

Explanation:

A motor capacitor must be selected according to the equipment manufacturer’s specifications. Matching only the voltage rating does not make a capacitor an appropriate replacement. Incorrect capacitance can affect motor starting, running current, torque, efficiency, and operating temperature and may contribute to premature motor failure. The technician should verify the required microfarad rating and voltage rating before installation and follow the manufacturer’s service information. Increasing capacitance in an attempt to make a motor run faster is not an acceptable repair method. Proper component selection protects the motor and helps ensure that the HVAC equipment operates within its intended electrical characteristics.

Question 10. Before placing a newly installed commercial HVAC system into service, the contractor wants to verify that the equipment performs according to the installation requirements. Which activity provides the most complete evaluation?

A. Check only the thermostat display

B. Perform system commissioning and compare measured conditions with design requirements

C. Increase the operating temperature until the unit stops

D. Run the equipment without checking electrical or mechanical conditions

Correct Answer. B. Perform system commissioning and compare measured conditions with design requirements

Explanation:

Commissioning provides a structured method for confirming that an HVAC installation operates as intended. Depending on the system, the contractor may verify electrical characteristics, airflow, refrigerant conditions, temperatures, pressures, controls, safety devices, equipment sequence, and other operating parameters. Measured results should be compared with the manufacturer’s specifications and applicable design requirements. Checking only the thermostat does not establish whether the system is performing correctly throughout its operating range. Likewise, forcing equipment to operate until a safety device trips is not an appropriate commissioning procedure. Proper commissioning can identify installation problems before they develop into operating, comfort, efficiency, or reliability issues.