Ohio HVAC Practice Test (Free)

Question 1

In a gas furnace, what is the primary function of the heat exchanger?

Accepted Answer

To transfer heat from combustion gases to the circulating air without mixing the two airstreams

Answer

To mix outdoor air with return air before combustion

Answer

To ignite the burners using an electric spark

Answer

To filter dust and debris from the return air

Question 2

In Ohio, who is eligible to sit for the OCILB HVAC contractor exam based on trade experience alone?

Accepted Answer

A person with 5 years of experience as a tradesperson in the HVAC trade immediately before applying

Answer

Anyone who has completed a single 40-hour HVAC training course

Answer

Any homeowner who has installed their own furnace

Answer

A person with 1 year of part-time HVAC helper work

Question 3

In a forced-air heating system, what problem is most commonly caused by a severely undersized return air duct?

Accepted Answer

Reduced airflow across the heat exchanger, which can trip the limit switch and cause short cycling

Answer

Excess refrigerant charge in the condenser

Answer

Increased gas valve pressure at the burner orifice

Answer

A drop in the thermostat's calibration accuracy

Question 4

What is the function of a hot surface igniter in a modern gas furnace?

Accepted Answer

It heats up electrically and ignites the gas at the burners, replacing a standing pilot light

Answer

It senses flue gas temperature to control the draft inducer speed

Answer

It regulates the thermostat's heat anticipator

Answer

It measures outdoor temperature to adjust furnace staging

Question 5

Why do high-efficiency condensing furnaces require a condensate drain?

Accepted Answer

Because they extract additional heat from flue gases, causing water vapor in the exhaust to condense into liquid

Answer

Because the blower motor is water-cooled

Answer

Because the gas valve requires periodic flushing with water

Answer

Because the heat exchanger is submerged in a water bath

Question 6

During a combustion analysis on a mid-efficiency furnace, a technician measures unusually high carbon monoxide readings in the flue gas along with low excess air. What does this combination most likely indicate?

Accepted Answer

Incomplete combustion due to insufficient combustion air supply

Answer

A properly tuned burner with ideal air-fuel ratio

Answer

An oversized gas orifice delivering too little gas pressure

Answer

A refrigerant leak in the indoor coil

Question 7

A heat pump in heating mode shows adequate airflow but insufficient heat output on a mild day, with the outdoor unit running continuously and frost forming heavily on the outdoor coil earlier than expected. What does this suggest?

Accepted Answer

A low refrigerant charge or defrost control malfunction reducing heat transfer efficiency

Answer

The thermostat is set to emergency heat mode as intended

Answer

The reversing valve is functioning correctly for cooling mode

Answer

The indoor blower is oversized for the ductwork

Question 8

In the basic refrigeration cycle, what is the primary function of the compressor?

Accepted Answer

To raise the pressure and temperature of refrigerant vapor so it can reject heat at the condenser

Answer

To lower refrigerant pressure before it enters the evaporator

Answer

To filter moisture and debris from the refrigerant

Answer

To meter the exact amount of refrigerant entering the evaporator

Question 9

What is superheat in a refrigeration system?

Accepted Answer

The temperature rise of refrigerant vapor above its saturation temperature at the measured pressure

Answer

The temperature drop of liquid refrigerant below its saturation temperature

Answer

The maximum temperature the compressor can safely reach

Answer

The temperature difference between indoor and outdoor air

Question 10

What is subcooling in an air conditioning system?

Accepted Answer

The amount liquid refrigerant is cooled below its saturation temperature at the measured pressure

Answer

The amount refrigerant vapor is heated above its saturation temperature

Answer

The temperature of the air leaving the evaporator coil

Answer

The pressure drop across the metering device