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100+ Free NV C-21 Refrigeration and Air Conditioning Practice Questions

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2026 Statistics

Key Facts: NV C-21 Refrigeration and Air Conditioning Exam

85 Q

Official Exam Questions

PSI Nevada Contractor CIB updated 3/25/2026

60 of 85 points

Passing Score

PSI Nevada Contractor CIB updated 3/25/2026

3 hours

Time Allowed

PSI Nevada Contractor CIB updated 3/25/2026

USD 95

PSI Exam Fee (one portion)

PSI Nevada Contractor CIB updated 3/25/2026

Open Book

Book Policy

PSI Nevada Contractor CIB updated 3/25/2026

Nevada C-21 Refrigeration and Air Conditioning Contractor Examination is the official NSCB/PSI open book exam: 85 questions, 60 of 85 points, 3 hours, USD 95 (bulletin 270, updated 3/25/2026). Official delivery: English.

Sample NV C-21 Refrigeration and Air Conditioning Practice Questions

Try these sample questions to test your NV C-21 Refrigeration and Air Conditioning exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Copper tube erected on the premises for a Nevada C-21 refrigerant circuit shall be which product?
A.Seamless Type ACR copper tube complying with ASTM B280 (or a listed ACR equivalent)
B.Type DWV copper drainage tube
C.Type M water tube joined with 50-50 solder
D.Soft polyethylene irrigation tubing
Explanation: UMC 2018 Chapter 11 requires seamless ACR (air-conditioning and refrigeration) copper, typically ASTM B280, for field-erected refrigerant piping. ACR tube is dehydrated, cleaned, and capped for refrigerant service. Type DWV and Type M water tube are plumbing products with the wrong cleanliness, wall, and joining rules.
2While brazing a copper ACR joint on a C-21 split-system line set, a dry nitrogen purge is used primarily to:
A.Increase the braze melting temperature so the joint cools faster
B.Pressurize the system to the high-side relief setting during the braze
C.Keep oxygen out of the tube so copper-oxide scale does not form inside the circuit
D.Replace the need for a post-braze pressure test
Explanation: A low-flow dry-nitrogen purge displaces oxygen while the tube is hot so internal copper oxide (scale) does not form and later travel into the TXV, filter-drier, or compressor. UMC Chapter 11 still requires a later inert-gas pressure test of the finished joints. The purge is not a substitute for that test and is not meant to reach relief pressure.
3Field-erected refrigerant pipe joints on a C-21 system shall be:
A.Left exposed for visual inspection and testing before they are covered or enclosed
B.Insulated and buried before anyone inspects them so the jacket is not delayed
C.Painted with aluminum paint in lieu of a pressure test
D.Soft-soldered with 50-50 plumber's solder when the refrigerant is Group A2 or A3
Explanation: UMC 2018 Chapter 11 requires refrigerant joints erected on the premises to remain exposed for visual inspection and testing before they are covered or enclosed. Covering a joint before the nitrogen test hides leaks. Group A2 and A3 joints are brazed, not soft-soldered.
4Per UMC 2018 Chapter 11, a positive-displacement C-21 system containing more than 6.6 pounds of refrigerant shall have stop valves:
A.Only at the liquid-receiver drain
B.Nowhere; stop valves are prohibited on refrigerant lines
C.Only on the condenser water piping
D.At the inlet and discharge of each compressor, compressor unit, or condensing unit, and at each liquid receiver (with listed exceptions)
Explanation: UMC 1110.1 requires stop valves at the compressor or condensing-unit inlet and discharge and at the liquid receiver on systems over 6.6 pounds so the equipment can be isolated. Listed factory equipment and smaller charges have exceptions. Water-side valves do not isolate refrigerant.
5A field-erected C-21 refrigeration system shall be pressure-tested on:
A.The high-pressure side only
B.The low-pressure side only
C.Both the high- and low-pressure sides, at not less than the lower of the design pressure or the relief-device setting (with listed factory-tested exceptions)
D.Neither side if the compressor nameplate is present
Explanation: UMC 2018 Chapter 11 field tests include both high and low sides. Test pressure is not less than the lower of design pressure or the relief setting taken from the condensing-unit or compressor nameplate. Factory-tested listed components are excepted. A nameplate identifies the pressure; it does not cancel the field test of the erected piping.
6Copper and copper-alloy refrigerant piping shall not be used with which refrigerant?
A.R-410A
B.R-134a
C.R-717 (ammonia)
D.R-22 in an existing listed system
Explanation: Ammonia (R-717) attacks copper and copper alloys. UMC/ASHRAE 15 industrial ammonia systems use steel (and specified alloys), never copper ACR. R-134a, R-410A, and existing R-22 systems are commonly piped in copper ACR.
7Under the 2018 UMC, field joints in copper C-21 refrigerant piping may be made by:
A.50-50 plumber's solder on every refrigerant, including Group A2 and A3
B.Solvent cement
C.Brazing, or listed press-connect fittings complying with UL 207 where the code allows them
D.Hose clamps and refrigeration tape
Explanation: UMC 2018 Chapter 11 allows brazed joints and listed press-connect refrigerant fittings that comply with UL 207. Soft 50-50 solder, solvent cement, and hose clamps are not refrigerant joints. Flammable-refrigerant (A2/A3) joints are brazed, not soldered.
8Refrigerant suction lines are insulated primarily to prevent condensation and heat gain. Where must the vapor retarder be placed?
A.Against the copper tube, under the insulation
B.On the outside of the insulation, sealed at every joint and penetration
C.Only on the compressor body
D.Vapor retarders are never used on suction lines
Explanation: Suction gas is below ambient dew point, so moisture tries to move inward. The vapor retarder belongs on the warm (outer) face of the insulation and must be continuous. Uninsulated or poorly jacketed suction pipe sweats, drips, and picks up heat that lowers compressor capacity. Liquid lines are usually left bare unless they can sweat.
9Per 2018 UMC Table 313.3, horizontal copper or copper-alloy pipe 1-1/2 inches and smaller shall be supported at intervals not exceeding:
A.6 feet
B.4 feet
C.10 feet
D.12 feet
Explanation: Table 313.3 requires 6-foot horizontal spacing for copper 1-1/2 inches and smaller (soldered, brazed, threaded, or mechanical). Copper 2 inches and larger may go 10 feet. Copper is more flexible than steel, so hangers are closer than the 12-foot steel water row.
10What is the maximum horizontal support spacing for 1/2-inch steel fuel-gas pipe under NFPA 54 2012 / UMC 2018 Table 1310.3.5.1?
A.4 feet
B.10 feet
C.6 feet
D.12 feet
Explanation: The fuel-gas support table allows a maximum of 6 feet between supports on 1/2-inch steel pipe. Three-quarter and 1-inch steel may go 8 feet; 1-1/4 inch and larger horizontal steel may go 10 feet. Do not use the 12-foot steel-water row on a gas line. CSST is supported per the manufacturer's instructions.

About the NV C-21 Refrigeration and Air Conditioning Exam

The Nevada C-21 Refrigeration and Air Conditioning Contractor Examination is the official Nevada State Contractors Board trade examination administered by PSI Services LLC. The official exam has 85 scored questions. Passing is 60 of 85 points in 3 hours. The examination is open book. Uniform Mechanical Code, 2018 and NFPA 54, 2012 (allowed in center). PSI lists USD 95 for one examination portion and USD 140 if taken with CMS; otherwise USD 95 per trade exam (Candidate Information Bulletin 270, updated 3/25/2026). NSCB requires a separate CMS examination for most new applicants, plus a USD 300 application fee and a USD 600 biennial license fee. This English-language MCQ bank is a study aid, not an official PSI form. It does not replace required trade experience, board approval, fingerprints, bonding, or the official examination.

Assessment

Open Book computer-based multiple-choice. Uniform Mechanical Code, 2018 and NFPA 54, 2012 (allowed in center)

Time Limit

3 hours

Passing Score

60 of 85 points

Exam Fee

USD 95 (PSI Services LLC (for the Nevada State Contractors Board))

NV C-21 Refrigeration and Air Conditioning Exam Content Outline

7%

Piping

Piping (6 items)

1%

Insulation

Insulation (1 items)

4%

Hangers and Supports

Hangers and Supports (3 items)

1%

Sound, Vibration and Seismic Control

Sound, Vibration and Seismic Control (1 items)

4%

Heating and Cooling Principles

Heating and Cooling Principles (3 items)

8%

Refrigerants and Refrigeration

Refrigerants and Refrigeration (7 items)

7%

Load Calculations

Load Calculations (6 items)

4%

Testing, Adjusting and Balancing

Testing, Adjusting and Balancing (3 items)

6%

Controls

Controls (5 items)

1%

Machine Room

Machine Room (1 items)

5%

A/C and Heat Pump Equipment

A/C and Heat Pump Equipment (4 items)

5%

Furnaces and Heaters

Furnaces and Heaters (4 items)

2%

Hydronics

Hydronics (2 items)

6%

Chimneys, Flues and Vents

Chimneys, Flues and Vents (5 items)

2%

Combustion Air

Combustion Air (2 items)

12%

Fuel Systems

Fuel Systems (10 items)

7%

Ducts

Ducts (6 items)

2%

Evaporative Cooling

Evaporative Cooling (2 items)

4%

Chillers

Chillers (3 items)

5%

Solar

Solar (4 items)

4%

Ventilation and Exhausts

Ventilation and Exhausts (3 items)

5%

Safety

Safety (4 items)

How to Pass the NV C-21 Refrigeration and Air Conditioning Exam

What You Need to Know

  • Passing score: 60 of 85 points
  • Assessment: Open Book computer-based multiple-choice. Uniform Mechanical Code, 2018 and NFPA 54, 2012 (allowed in center)
  • Time limit: 3 hours
  • Exam fee: USD 95

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

NV C-21 Refrigeration and Air Conditioning Study Tips from Top Performers

1Distribute study time to the official bulletin 270 content outline (updated 3/25/2026)
2Use only the PSI-listed references; temporary tabs such as Post-it notes are prohibited
3Confirm NSCB experience documentation before scheduling with PSI
4This bank is an English-language MCQ study aid, not an official PSI form

Frequently Asked Questions

How many questions are on the Nevada C-21 Refrigeration and Air Conditioning Contractor Examination?

The official PSI examination has 85 scored questions. Passing is 60 of 85 points within 3 hours (Candidate Information Bulletin 270, updated 3/25/2026).

How much does the NV C-21 exam cost?

PSI lists USD 95 for one examination portion. Two portions cost USD 140 only if the second portion is CMS. NSCB charges a separate USD 300 application fee and USD 600 biennial license fee.

Is the NV C-21 exam open book?

Yes. PSI lists this examination as open book. Uniform Mechanical Code, 2018 and NFPA 54, 2012 (allowed in center)

Do I still need the CMS examination?

CMS is the required Nevada business-and-law examination. Most new applicants must pass CMS and a trade examination for the requested classification. In most cases you will not retake an exam if you have actively served as a qualified employee in the same classification within the last four years.