— 150 QUESTIONS HVAC/MECHANICAL
CONTRACTOR SUBJECT AREAS REFLECTED IN
CURRENT PSI MATERIALS, INCLUDING
ELECTRICAL/CONTROLS, PIPING, HEATING AND
COOLING, REFRIGERATION, FUEL GAS,
COMBUSTION/VENTING, DUCTS, LOAD
CALCULATIONS, AND SAFETY.
What is the primary purpose of a thermostat in an HVAC
system?
A. Increase refrigerant pressure
B. Sense space temperature and control system operation
C. Remove moisture from refrigerant
D. Increase airflow
Correct Answer: B
,Rationale: A thermostat senses room temperature and signals
heating or cooling equipment to maintain the selected
setpoint.
Which component removes heat from indoor air during normal
air-conditioning operation?
A. Condenser
B. Compressor
C. Evaporator coil
D. Receiver
Correct Answer: C
Rationale: The evaporator absorbs heat from the conditioned
space as refrigerant evaporates inside the coil.
What is the primary function of a compressor?
A. Reduce refrigerant temperature
B. Circulate and raise the pressure of refrigerant vapor
C. Remove dust from air
D. Control humidity directly
Correct Answer: B
,Rationale: The compressor raises refrigerant vapor pressure
and temperature and moves refrigerant through the system.
Which component rejects heat to the outdoor environment?
A. Evaporator
B. Condenser
C. Expansion valve
D. Accumulator
Correct Answer: B
Rationale: The condenser transfers heat from the refrigerant
to the surrounding outdoor air or another cooling medium.
What happens to refrigerant pressure across a typical
metering device?
A. It increases substantially
B. It remains constant
C. It decreases
D. It becomes atmospheric
Correct Answer: C
, Rationale: The metering device creates a pressure drop that
allows high-pressure liquid refrigerant to enter the low-
pressure evaporator.
What is superheat?
A. Refrigerant temperature above its saturation temperature
B. Refrigerant temperature below freezing
C. Condenser pressure above design pressure
D. Liquid temperature below saturation
Correct Answer: A
Rationale: Superheat is the amount by which vapor
temperature exceeds its saturation temperature at a given
pressure.
What is subcooling?
A. Vapor temperature above saturation
B. Liquid temperature below its saturation temperature
C. Compressor temperature above normal
D. Air temperature below room temperature
Correct Answer: B