Download Nevada (NV) C-21B Air Conditioning Contractor Practice Exam 2026 Exam Overview The Nevad and more Exams Engineering in PDF only on Docsity!
Nevada (NV) C-21B Air Conditioning Contractor Practice Exam 2026 Exam Overview The Nevada C-21B Air Conditioning Contractor exam is an open-book trade assessment required for licensing to install and repair residential and commercial HVAC systems. It is administered by PSI and must be paired with the Construction Management Survey (CMS) exam to obtain a valid Nevada license.
Exam DomainWeight Load Calculations (Manual J, S, D)~15% Systems & Equipment~25% Controls & Electrical~15% Piping & Refrigerants (EPA 608)~20% General Knowledge & Safety (IMC, NEC, OSHA)~25%
Minimum Passing Score: 70%
VERSION 1: PRACTICE EXAM (100 Questions)
SECTION 1: HVAC FUNDAMENTALS & THERMODYNAMICS (Questions 1-20)
- What is the primary function of an air conditioning system as defined for a C-21B contractor in Nevada?
- A) To provide complete building automation
- B) To regulate indoor temperature and humidity
- C) To serve as a primary heating source
- D) To replace mechanical ventilation systems Answer: B Rationale: Under NAC 624.380, the C-21B subclassification specifically covers equipment that uses evaporation, refrigeration, boilers, or combustion for the control of air temperatures, including humidity controls.
- What is the primary difference between sensible heat and latent heat?
- A) Sensible heat changes temperature; latent heat changes phase
- B) Sensible heat changes pressure; latent heat changes volume
- C) Sensible heat is measured in BTU/hr; latent heat in kW
- D) Sensible heat is only in cooling; latent heat only in heating Answer: A Rationale: Sensible heat results in a temperature change without a phase change, while latent heat involves a phase change (e.g., condensation or evaporation) at constant temperature.
- B) Convection
- C) Radiation
- D) All three equally Answer: B Rationale: Forced-air furnaces rely on convection to move heated air across the heat exchanger and into the ductwork.
- What does an "A1" refrigerant classification signify according to ASHRAE?
- A) Low toxicity, high flammability
- B) Low toxicity, non-flammable
- C) High toxicity, non-flammable
- D) High toxicity, high flammability Answer: B Rationale: ASHRAE "A1" denotes refrigerants that are mildly toxic (Class A) and non-flammable (Class 1), such as R-410A.
- Section 608 of the EPA regulations primarily addresses which of the following?
- A) Energy efficiency standards for HVAC equipment
- B) Safe handling and disposal of refrigerants
- C) Minimum ventilation rates for commercial buildings
- D) Building insulation requirements
Answer: B Rationale: EPA Section 608 regulates the safe handling, recovery, recycling, and disposal of refrigerants to prevent ozone depletion.
- What is the term for heat that changes the temperature of a substance without changing its physical state?
- A) Latent heat
- B) Superheat
- C) Subcooling
- D) Sensible heat Answer: D Rationale: Sensible heat is the energy added or removed that causes a change in temperature. Latent heat causes a phase change without a temperature change.
- Which component creates the pressure drop that allows the refrigerant to expand and cool before entering the evaporator?
- A) Accumulator
- B) Compressor
- C) Metering device (TXV or piston)
- D) Receiver
Rationale: Latent heat is "hidden" heat. In HVAC, it is the energy required to evaporate water (condensate) or refrigerant, contributing to humidity control. Sensible heat changes temperature.
- What is the primary function of the evaporator coil in an air conditioning system?
- A) To compress refrigerant
- B) To absorb heat from indoor air
- C) To expel heat to the outside
- D) To control refrigerant flow Answer: B Rationale: The evaporator coil contains cold refrigerant that absorbs heat from the warm indoor air blowing over it, cooling the air before it is circulated back into the space.
- Which component of the refrigeration cycle raises the pressure and temperature of the refrigerant?
- A) Condenser
- B) Evaporator
- C) Expansion valve
- D) Compressor Answer: D
Rationale: The compressor compresses low-pressure vapor into high-pressure, high- temperature vapor.
- Which refrigerant is classified as a Class III ozone-depleting substance?
- A) R-410A
- B) R- 22
- C) R-134a
- D) R-404A Answer: B Rationale: R-22 (chlorodifluoromethane) is a Class III ozone-depleting refrigerant and is being phased out.
- What is subcooling?
- A) The temperature of the refrigerant vapor above its saturation point
- B) The temperature of the liquid refrigerant below its saturation point
- C) The temperature difference across the evaporator
- D) The outdoor ambient temperature Answer: B Rationale: Subcooling is the difference between the actual temperature of the liquid refrigerant and its saturation temperature at the same pressure.
- A) Large shopping malls
- B) Older homes or additions where installing ductwork is cost-prohibitive
- C) High-rise commercial buildings
- D) Industrial warehouses Answer: B Rationale: Ductless mini-split systems are ideal for older homes or additions where installing ductwork is cost-prohibitive or impractical.
- Variable Refrigerant Flow (VRF) systems are particularly beneficial for:
- A) Single-room window units
- B) Large buildings requiring individualized zone temperature control
- C) Buildings that do not require zoning
- D) Areas with consistent humidity only Answer: B Rationale: VRF systems allow for customized temperature control in different zones or rooms within large commercial or residential buildings by modulating the flow of refrigerant to multiple indoor units.
- In Nevada, the minimum required licensing exam score for a C-21B contractor is:
- C) 70%
- D) 75%
Answer: C Rationale: Nevada's C-21B (Air Conditioning Contractor) exam requires a minimum passing score of 70%.
SECTION 2: HVAC SYSTEMS & EQUIPMENT (Questions 21-40)
- What is the typical temperature drop (delta T) across an evaporator coil for a properly charged system under standard conditions?
- A) 5-10°F
- B) 10-15°F
- C) 15-20°F
- D) 20-25°F Answer: C Rationale: A temperature drop of 18-22°F is typical for a properly charged system under standard conditions.
- A homeowner complains that their air conditioner runs constantly but barely cools the house. You measure the return air temperature at 75°F and the supply air temperature at 62°F. What is the temperature drop, and is it within the normal range?
- D) Centrifugal Answer: B Rationale: Scroll compressors are the most common type used in modern residential air conditioning systems due to their efficiency, reliability, and quiet operation.
- What is the purpose of an accumulator in a refrigeration system?
- A) To store liquid refrigerant
- B) To prevent liquid refrigerant from reaching the compressor
- C) To filter refrigerant
- D) To control refrigerant flow Answer: B Rationale: An accumulator prevents liquid refrigerant from reaching the compressor, which could cause damage.
- In a heat pump system, what is the purpose of the defrost cycle?
- A) To cool the indoor coil
- B) To remove frost from the outdoor coil
- C) To increase heating capacity
- D) To reverse the refrigerant flow Answer: B
Rationale: The defrost cycle removes frost that accumulates on the outdoor coil during heating mode in cold weather.
- Which metering device is most commonly used in modern residential air conditioning systems?
- A) Capillary tube
- B) Fixed orifice
- C) Thermostatic expansion valve (TXV)
- D) Float valve Answer: C Rationale: The thermostatic expansion valve (TXV) is the most common metering device in modern residential systems, providing precise refrigerant flow control.
- What is the primary advantage of a two-stage compressor?
- A) Lower initial cost
- B) Improved efficiency and humidity control
- C) Simpler installation
- D) Fewer moving parts Answer: B Rationale: Two-stage compressors provide improved efficiency and better humidity control by operating at two different capacities.
- Which type of furnace has the highest efficiency?
- A) Natural draft
- B) Induced draft (80% AFUE)
- C) Condensing (90%+ AFUE)
- D) Atmospheric Answer: C Rationale: Condensing furnaces achieve 90%+ AFUE by capturing heat from flue gases that would otherwise be lost.
- What is the minimum slope required for a condensate drain line?
- A) 1/8 inch per foot
- B) 1/4 inch per foot
- C) 1/2 inch per foot
- D) 1 inch per foot Answer: B Rationale: Gravity-fed condensate lines must maintain a minimum slope of 1/4 inch per foot (2% grade).
- What is the primary purpose of a condensate drain line safety switch (float switch)?
- A) To improve efficiency
- B) To shut down the system if the drain line clogs
- C) To measure condensate flow
- D) To add water to the system Answer: B Rationale: The float switch shuts down the system if the condensate drain line clogs, preventing water damage.
- What is the typical SEER rating for a high-efficiency residential air conditioning system?
- A) 10-12 SEER
- B) 13-14 SEER
- C) 16+ SEER
- D) 20+ SEER Answer: C Rationale: High-efficiency residential air conditioning systems typically have a SEER rating of 16 or higher.
- What is the purpose of an expansion tank in a hydronic heating system?
- A) To store hot water
- B) To absorb thermal expansion of water
- C) To circulate water
- D) To heat water
- Which refrigerant is commonly used in modern residential air conditioning systems?
- A) R- 22
- B) R-410A
- C) R- 12
- D) R-134a Answer: B Rationale: R-410A is the most common refrigerant in modern residential air conditioning systems, replacing R-22.
- What is the purpose of a thermostatic expansion valve (TXV)?
- A) To compress refrigerant
- B) To control the flow of refrigerant into the evaporator
- C) To condense refrigerant
- D) To store refrigerant Answer: B Rationale: The TXV controls the flow of refrigerant into the evaporator to maintain proper superheat.
- Which component is responsible for removing heat from the refrigerant in the refrigeration cycle?
- A) Evaporator
- B) Compressor
- C) Condenser
- D) Expansion valve Answer: C Rationale: The condenser removes heat from the refrigerant, causing it to condense from a gas to a liquid.
SECTION 3: LOAD CALCULATIONS & DUCT DESIGN (Questions 41-55)
- What is the primary purpose of a Manual J load calculation?
- A) To size ductwork
- B) To determine heating and cooling loads
- C) To select equipment
- D) To design the refrigerant piping Answer: B Rationale: Manual J is used to determine residential heating and cooling loads based on insulation, orientation, windows, occupancy, and other factors.
