Free HVAC Practice Test (20 Questions) | ExamsLib

Question 1

In a heat pump system, what is the purpose of the reversing valve?

Accepted Answer

It switches refrigerant flow direction so the system can operate in both heating and cooling modes

Answer

It reverses the direction of compressor rotation to prevent damage during startup

Answer

It reverses the polarity of the thermostat signal during defrost cycles

Answer

It redirects airflow from supply to return during emergency heat mode

Question 2

During refrigerant recovery from a system with a hermetic compressor larger than 200 horsepower, what is the required vacuum level (inches of mercury) before the system is considered recovered, assuming the recovery machine was manufactured after November 15, 1993?

Accepted Answer

10 inches Hg

Answer

0 inches Hg

Answer

4 inches Hg

Answer

15 inches Hg

Question 3

A technician finds a system leaking refrigerant. Under EPA Section 608, what is the maximum allowable annual leak rate for a commercial refrigeration system holding more than 50 pounds of refrigerant before repair is required?

Accepted Answer

20%

Answer

5%

Answer

10%

Answer

30%

Question 4

Which EPA 608 certification type covers technicians who service small appliances containing five pounds or less of refrigerant, such as household refrigerators and window AC units?

Accepted Answer

Type I

Answer

Type II

Answer

Type III

Answer

Universal

Question 5

Which thermostat terminal is typically used to energize the air handler fan independently, such as when the occupant selects 'Fan On' on a 24-volt thermostat system?

Accepted Answer

G (fan)

Answer

W (heat)

Answer

Y (compressor)

Answer

C (common)

Question 6

A condensing gas furnace produces liquid condensate in its secondary heat exchanger. Where should this condensate drain, and what safety device confirms proper combustion airflow before ignition?

Accepted Answer

Through a neutralizer into a sanitary drain; an induced draft motor with pressure switch proves combustion airflow

Answer

Into a floor drain; a barometric damper prevents backdrafting

Answer

Through a humidifier pad into the ductwork; a limit switch prevents overheating

Answer

Into an outdoor condensate pump; a draft hood prevents negative pressure

Question 7

A technician recovers refrigerant from a large commercial chiller using R-123. After recovery, what vacuum level must be achieved, and which EPA 608 type covers this equipment?

Accepted Answer

29 inches Hg vacuum; Type III

Answer

25 inches Hg vacuum; Type II

Answer

4 inches Hg vacuum; Type I

Answer

10 inches Hg vacuum; Universal

Question 8

An air-cooled condensing unit is operating on a 95 degree F day. The technician reads a high-side pressure corresponding to a condensing temperature of 125 degrees F. What is the condenser split (also called condenser temperature difference)?

Accepted Answer

30 degrees F

Answer

125 degrees F

Answer

95 degrees F

Answer

220 degrees F

Question 9

A compressor discharge temperature on an R-22 system reads 220 degrees F. What is the most likely cause, and what is the potential consequence if left uncorrected?

Accepted Answer

High superheat caused by low charge or a restricted metering device; compressor overheating can break down oil and damage valves

Answer

Low superheat caused by refrigerant overcharge; the condenser coil will ice over

Answer

High subcooling caused by a flooded condenser; the liquid receiver will overpressurize

Answer

Non-condensable gas causing high suction pressure and low discharge temperature

Question 10

A variable refrigerant flow (VRF) system uses an electronic expansion valve (EEV) in each indoor unit. What key advantage does this provide over a fixed orifice system serving multiple zones?

Accepted Answer

EEVs allow each indoor unit to independently modulate refrigerant flow to match its zone load, improving efficiency and comfort

Answer

EEVs eliminate the need for any refrigerant, using only chilled water

Answer

EEVs prevent any superheat from developing, which reduces compressor work

Answer

EEVs convert refrigerant directly to water vapor, eliminating condensate

Free HVAC Practice Test

Question 1

In a heat pump system, what is the purpose of the reversing valve?

Question 2

During refrigerant recovery from a system with a hermetic compressor larger than 200 horsepower, what is the required vacuum level (inches of mercury) before the system is considered recovered, assuming the recovery machine was manufactured after November 15, 1993?

Question 3

A technician finds a system leaking refrigerant. Under EPA Section 608, what is the maximum allowable annual leak rate for a commercial refrigeration system holding more than 50 pounds of refrigerant before repair is required?

Question 4

Which EPA 608 certification type covers technicians who service small appliances containing five pounds or less of refrigerant, such as household refrigerators and window AC units?

Question 5

Which thermostat terminal is typically used to energize the air handler fan independently, such as when the occupant selects 'Fan On' on a 24-volt thermostat system?

Question 6

A condensing gas furnace produces liquid condensate in its secondary heat exchanger. Where should this condensate drain, and what safety device confirms proper combustion airflow before ignition?

Question 7

A technician recovers refrigerant from a large commercial chiller using R-123. After recovery, what vacuum level must be achieved, and which EPA 608 type covers this equipment?

Question 8

An air-cooled condensing unit is operating on a 95 degree F day. The technician reads a high-side pressure corresponding to a condensing temperature of 125 degrees F. What is the condenser split (also called condenser temperature difference)?

Question 9

A compressor discharge temperature on an R-22 system reads 220 degrees F. What is the most likely cause, and what is the potential consequence if left uncorrected?

Question 10

A variable refrigerant flow (VRF) system uses an electronic expansion valve (EEV) in each indoor unit. What key advantage does this provide over a fixed orifice system serving multiple zones?

Question 11

A refrigerant cylinder is painted green. Which refrigerant does this color coding indicate?

Question 12

A residential forced-air system moves 1,200 CFM of air. The supply air temperature is 120 degrees F and the return air temperature is 70 degrees F. Using the sensible heat formula Q = 1.08 x CFM x delta-T, what is the system's heating output in BTU/hr?

Question 13

During furnace operation, the high-limit switch trips and shuts off the gas valve. What is the most common cause?

Question 14

Which refrigerant is classified as an HFC and has zero ozone depletion potential (ODP)?

Question 15

A technician measures total system superheat on an R-22 system and finds it is 35 degrees F. What condition does this most likely indicate?

Question 16

Question 17

What does the term 'recycling' mean in the context of refrigerant handling under EPA 608?

Question 18

What is the primary difference between a single-stage and a two-stage gas furnace?

Question 19

A gas furnace has an input rating of 100,000 BTU/hr and an AFUE of 80%. What is its approximate heating output?

Question 20

What is the function of the compressor in a vapor-compression refrigeration system?