Certified Air Conditioning Systems
Technician (CAST) – 2026
Edition|||Questions And Answers
With Rationales/Graded A+/2026
Update/100% Correct /Instant
Download
School Level: Technical / Vocational
Total Questions: 85
Time Allowed: 120 minutes
Passing Score: 70%
Format: Multiple Choice
Section 1: Fundamentals of Refrigeration (Questions 1–15)
1. In the vapor-compression refrigeration cycle, the component where refrigerant
changes from low-pressure vapor to high-pressure vapor is the:
a) Evaporator
b) Condenser
c) Compressor
d) Expansion valve
Rationale: The compressor increases pressure and temperature of the refrigerant
vapor, preparing it for condensation.
2. Which refrigerant is being phased down globally under the Kigali Amendment
(effective stricter limits in 2026)?
a) R-410A
b) R-134a (also R-410A, but R-134a is a high-GWP HFC targeted heavily)
c) R-290
d) R-744
,Rationale: R-134a has a GWP of 1,430; the Kigali Amendment accelerates HFC
phase-downs. (Note: R-410A is also correct, but for single answer, R-134a is
commonly tested.)
3. The superheat of a system is defined as:
a) Temperature of refrigerant in the condenser minus saturation temperature
b) Suction line temperature minus evaporator saturation temperature
c) Liquid line temperature minus condenser saturation temperature
d) Discharge line temperature minus compressor inlet temperature
Rationale: Superheat ensures no liquid enters the compressor.
4. A thermostatic expansion valve (TXV) responds to changes in:
a) Evaporator pressure
b) Condenser pressure
c) Superheat
d) Subcooling
Rationale: The TXV bulb senses evaporator outlet temperature to modulate
refrigerant flow.
5. What is the typical subcooling range for a modern AC system using R-410A?
a) 0–5°F
b) 8–15°F
c) 20–30°F
d) 35–40°F
Rationale: Proper subcooling (typically 10–15°F for TXV systems) ensures
efficient condenser performance.
6. Which of the following is a natural refrigerant with an Ozone Depletion
Potential (ODP) of 0 and GWP of 1?
a) R-32
b) R-744 (CO₂)
c) R-1234yf
d) R-134a
Rationale: CO₂ is natural, GWP=1, ODP=0; R-32 and R-1234yf are synthetic but
low GWP.
7. The primary function of an accumulator is to:
a) Store excess refrigerant
b) Prevent liquid refrigerant from entering the compressor
c) Filter debris
, d) Increase subcooling
Rationale: Accumulators trap liquid and allow only vapor to return to the
compressor.
8. What is the pressure-enthalpy diagram used for?
a) Electrical troubleshooting
b) Analyzing refrigeration cycle performance
c) Duct sizing
d) Psychrometric calculations
Rationale: P-h diagrams show compressor work, heat rejection, and cooling effect.
9. A system has a low suction pressure and high superheat. The most likely cause
is:
a) Overcharged refrigerant
b) Underfeeding TXV or restricted filter drier
c) Inefficient compressor
d) Dirty condenser coil
Rationale: Low suction + high superheat = starved evaporator.
10. Which refrigerant is mildly flammable (A2L) and widely used in 2026 split
systems?
a) R-22
b) R-32
c) R-410A
d) R-502
Rationale: R-32 (GWP 675) is replacing R-410A in many new systems due to
lower GWP and higher efficiency.
11. The compression ratio is calculated as:
a) Suction pressure / Discharge pressure
b) Discharge pressure (absolute) / Suction pressure (absolute)
c) Discharge pressure (gauge) × Suction pressure (gauge)
d) (Condenser temp – Evaporator temp) / 2
Rationale: High compression ratios reduce efficiency and can overheat the
compressor.
12. What does a crankcase heater prevent?
a) Refrigerant migration during off-cycle
b) Liquid slugging on startup
c) High discharge temperature
Technician (CAST) – 2026
Edition|||Questions And Answers
With Rationales/Graded A+/2026
Update/100% Correct /Instant
Download
School Level: Technical / Vocational
Total Questions: 85
Time Allowed: 120 minutes
Passing Score: 70%
Format: Multiple Choice
Section 1: Fundamentals of Refrigeration (Questions 1–15)
1. In the vapor-compression refrigeration cycle, the component where refrigerant
changes from low-pressure vapor to high-pressure vapor is the:
a) Evaporator
b) Condenser
c) Compressor
d) Expansion valve
Rationale: The compressor increases pressure and temperature of the refrigerant
vapor, preparing it for condensation.
2. Which refrigerant is being phased down globally under the Kigali Amendment
(effective stricter limits in 2026)?
a) R-410A
b) R-134a (also R-410A, but R-134a is a high-GWP HFC targeted heavily)
c) R-290
d) R-744
,Rationale: R-134a has a GWP of 1,430; the Kigali Amendment accelerates HFC
phase-downs. (Note: R-410A is also correct, but for single answer, R-134a is
commonly tested.)
3. The superheat of a system is defined as:
a) Temperature of refrigerant in the condenser minus saturation temperature
b) Suction line temperature minus evaporator saturation temperature
c) Liquid line temperature minus condenser saturation temperature
d) Discharge line temperature minus compressor inlet temperature
Rationale: Superheat ensures no liquid enters the compressor.
4. A thermostatic expansion valve (TXV) responds to changes in:
a) Evaporator pressure
b) Condenser pressure
c) Superheat
d) Subcooling
Rationale: The TXV bulb senses evaporator outlet temperature to modulate
refrigerant flow.
5. What is the typical subcooling range for a modern AC system using R-410A?
a) 0–5°F
b) 8–15°F
c) 20–30°F
d) 35–40°F
Rationale: Proper subcooling (typically 10–15°F for TXV systems) ensures
efficient condenser performance.
6. Which of the following is a natural refrigerant with an Ozone Depletion
Potential (ODP) of 0 and GWP of 1?
a) R-32
b) R-744 (CO₂)
c) R-1234yf
d) R-134a
Rationale: CO₂ is natural, GWP=1, ODP=0; R-32 and R-1234yf are synthetic but
low GWP.
7. The primary function of an accumulator is to:
a) Store excess refrigerant
b) Prevent liquid refrigerant from entering the compressor
c) Filter debris
, d) Increase subcooling
Rationale: Accumulators trap liquid and allow only vapor to return to the
compressor.
8. What is the pressure-enthalpy diagram used for?
a) Electrical troubleshooting
b) Analyzing refrigeration cycle performance
c) Duct sizing
d) Psychrometric calculations
Rationale: P-h diagrams show compressor work, heat rejection, and cooling effect.
9. A system has a low suction pressure and high superheat. The most likely cause
is:
a) Overcharged refrigerant
b) Underfeeding TXV or restricted filter drier
c) Inefficient compressor
d) Dirty condenser coil
Rationale: Low suction + high superheat = starved evaporator.
10. Which refrigerant is mildly flammable (A2L) and widely used in 2026 split
systems?
a) R-22
b) R-32
c) R-410A
d) R-502
Rationale: R-32 (GWP 675) is replacing R-410A in many new systems due to
lower GWP and higher efficiency.
11. The compression ratio is calculated as:
a) Suction pressure / Discharge pressure
b) Discharge pressure (absolute) / Suction pressure (absolute)
c) Discharge pressure (gauge) × Suction pressure (gauge)
d) (Condenser temp – Evaporator temp) / 2
Rationale: High compression ratios reduce efficiency and can overheat the
compressor.
12. What does a crankcase heater prevent?
a) Refrigerant migration during off-cycle
b) Liquid slugging on startup
c) High discharge temperature
