CALIFORNIA CONTRACTORS STATE LICENSE
BOARD (CSLB) C-20 HVAC EXAM, QUESTIONS
AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF.
1. According to the California Mechanical Code, what is the minimum
required clearance between a single-wall metal vent connector and
combustible materials?
A) 1 inch
B) 6 inches
C) 12 inches
D) 18 inches
Reason: Code specifies 6 in. clearance as the minimum safe distance for
single-wall vent connectors to combustibles under typical conditions.
2. When calculating a residential heating load for sizing HVAC
equipment, which factor is typically considered?
A) The color of the interior walls
B) The number of trees on the property
C) The building’s insulation levels
D) The make and model of the HVAC equipment
Reason: Insulation levels directly affect heat loss/gain; wall color or
trees don’t significantly impact load calculations, while equipment
make/model is chosen after load determination.
,3. In a gas furnace, what is the function of a thermocouple?
A) It is a safety control for the fan
B) It is a safety device that confirms the existence of a pilot flame
C) It is a safety device for electronic ignition systems
D) It is a safety device that controls the thermostat
Reason: The thermocouple senses the pilot flame; if the flame goes out,
it shuts off gas to prevent leaks.
4. What does the abbreviation SEER stand for, regarding
air-conditioning system efficiency?
A) Super Energized Electric Resistor
B) Safety Exhaust Expansion Ratio
C) Seasonal Energy Efficiency Ratio
D) Standard Equipment Efficiency Rating
Reason: SEER is defined as Seasonal Energy Efficiency Ratio, used to
compare A/C unit efficiency over a cooling season.
5. In a refrigeration cycle, where does the refrigerant absorb heat from
the air or medium being cooled?
A) Compressor
B) Expansion Valve
C) Condenser
D) Evaporator
Reason: The evaporator is the part of the HVAC system where
refrigerant absorbs heat, cooling the surrounding air or medium.
6. What component typically regulates the amount of refrigerant
entering the evaporator based on load demand?
,A) Compressor
B) Condenser
C) Sight glass
D) Thermostatic Expansion Valve (TXV)
Reason: A TXV adjusts refrigerant flow into the evaporator dynamically,
ensuring proper cooling and preventing floodback.
7. Before putting a newly installed refrigerant line into operation, what
must be done?
A) Wash with detergent
B) Paint it
C) Pressure test and evacuate the line
D) Fill with oil
Reason: Pressure testing and evacuation ensure there are no leaks and
that moisture/contaminants are removed before charging the system.
8. What is the primary purpose of lockout/tagout procedures in HVAC
maintenance under workplace safety regulations?
A) To identify hazardous materials
B) To prevent unexpected startup of machinery during service or
maintenance
C) To track employee work hours
D) To control airborne contaminants
Reason: Lockout/tagout ensures machinery/equipment cannot be
energized while being serviced, preventing accidental start-up and
injury.
, 9. In ductwork fabrication for a rectangular duct, which type of fastener
is commonly used?
A) Circular
B) V-type
C) S-type
D) Angular
Reason: S-fasteners (S-cleats) are standard for connecting rectangular
or square duct seams because they offer a secure join and proper
alignment.
10. What is the typical control circuit voltage for a residential HVAC
thermostat?
A) 120 V
B) 48 V
C) 24 V
D) 12 V
Reason: Most residential HVAC systems use a 24 volt control circuit for
thermostats — standard in the industry for safe control signaling.
11. Which type of pipe is commonly used for refrigerant lines in HVAC
systems?
A) Black iron
B) PVC
C) Copper
D) Galvanized steel
Reason: Copper offers excellent thermal conductivity, is compatible with
refrigerants and refrigerant oils, and resists corrosion better than other
listed materials.
BOARD (CSLB) C-20 HVAC EXAM, QUESTIONS
AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF.
1. According to the California Mechanical Code, what is the minimum
required clearance between a single-wall metal vent connector and
combustible materials?
A) 1 inch
B) 6 inches
C) 12 inches
D) 18 inches
Reason: Code specifies 6 in. clearance as the minimum safe distance for
single-wall vent connectors to combustibles under typical conditions.
2. When calculating a residential heating load for sizing HVAC
equipment, which factor is typically considered?
A) The color of the interior walls
B) The number of trees on the property
C) The building’s insulation levels
D) The make and model of the HVAC equipment
Reason: Insulation levels directly affect heat loss/gain; wall color or
trees don’t significantly impact load calculations, while equipment
make/model is chosen after load determination.
,3. In a gas furnace, what is the function of a thermocouple?
A) It is a safety control for the fan
B) It is a safety device that confirms the existence of a pilot flame
C) It is a safety device for electronic ignition systems
D) It is a safety device that controls the thermostat
Reason: The thermocouple senses the pilot flame; if the flame goes out,
it shuts off gas to prevent leaks.
4. What does the abbreviation SEER stand for, regarding
air-conditioning system efficiency?
A) Super Energized Electric Resistor
B) Safety Exhaust Expansion Ratio
C) Seasonal Energy Efficiency Ratio
D) Standard Equipment Efficiency Rating
Reason: SEER is defined as Seasonal Energy Efficiency Ratio, used to
compare A/C unit efficiency over a cooling season.
5. In a refrigeration cycle, where does the refrigerant absorb heat from
the air or medium being cooled?
A) Compressor
B) Expansion Valve
C) Condenser
D) Evaporator
Reason: The evaporator is the part of the HVAC system where
refrigerant absorbs heat, cooling the surrounding air or medium.
6. What component typically regulates the amount of refrigerant
entering the evaporator based on load demand?
,A) Compressor
B) Condenser
C) Sight glass
D) Thermostatic Expansion Valve (TXV)
Reason: A TXV adjusts refrigerant flow into the evaporator dynamically,
ensuring proper cooling and preventing floodback.
7. Before putting a newly installed refrigerant line into operation, what
must be done?
A) Wash with detergent
B) Paint it
C) Pressure test and evacuate the line
D) Fill with oil
Reason: Pressure testing and evacuation ensure there are no leaks and
that moisture/contaminants are removed before charging the system.
8. What is the primary purpose of lockout/tagout procedures in HVAC
maintenance under workplace safety regulations?
A) To identify hazardous materials
B) To prevent unexpected startup of machinery during service or
maintenance
C) To track employee work hours
D) To control airborne contaminants
Reason: Lockout/tagout ensures machinery/equipment cannot be
energized while being serviced, preventing accidental start-up and
injury.
, 9. In ductwork fabrication for a rectangular duct, which type of fastener
is commonly used?
A) Circular
B) V-type
C) S-type
D) Angular
Reason: S-fasteners (S-cleats) are standard for connecting rectangular
or square duct seams because they offer a secure join and proper
alignment.
10. What is the typical control circuit voltage for a residential HVAC
thermostat?
A) 120 V
B) 48 V
C) 24 V
D) 12 V
Reason: Most residential HVAC systems use a 24 volt control circuit for
thermostats — standard in the industry for safe control signaling.
11. Which type of pipe is commonly used for refrigerant lines in HVAC
systems?
A) Black iron
B) PVC
C) Copper
D) Galvanized steel
Reason: Copper offers excellent thermal conductivity, is compatible with
refrigerants and refrigerant oils, and resists corrosion better than other
listed materials.
