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Michigan Unlimited Refrigeration & Air Conditioning Service
(Classification H) Practice Exam
Here are 200 multiple‑choice questions designed to mirror the official PSI Michigan Unlimited Refrigeration & Air Conditioning Service exam. The domains covered include Michigan Law & Licensing, EPA Section 608 Regulations, Refrigeration Cycle & Components, Electrical & Controls, System Design & Load Calculations, Psychrometrics & Airflow, Troubleshooting & Diagnostics, and Piping, Brazing & Safety. Exam Format: Closed book; 50–60 questions (practice set includes 200 with detailed answer rationales). Passing Score: 75% (official exam).
Domain 1: Michigan Law & Licensing Question 1: Which Michigan law establishes the licensing requirements for Unlimited (Classification H) refrigeration contractors?
- A) Michigan Electrical Code (PA 230)
- B) Michigan Skilled Trades Regulation Act (PA 407)
- C) Michigan Building Code
- D) Michigan Occupational Safety Act Answer: B Explanation: PA 407 of 2016, the Michigan Skilled Trades Regulation Act, defines licensure, renewal, and duties for Unlimited refrigeration contractors. New applicants must also reference PA 230 for application procedures.
Question 2: Under the Michigan Mechanical Code, a permit is required for which of the following actions?
- A) Replacing a broken fan belt on an existing system
- B) Adding a new refrigeration loop to an existing commercial kitchen
- C) Cleaning the condenser coils of a rooftop unit
- D) Adjusting thermostat setpoints on a residential AC Answer: B Explanation: Adding a new refrigeration loop constitutes an alteration that triggers a permit requirement; minor repairs like belt replacement and routine maintenance do not. Question 3: What is the minimum work experience required to qualify for the Unlimited Refrigeration license examination in Michigan?
- A) 1 year
- B) 2 years
- C) 3 years
- D) 5 years Answer: C Explanation: An applicant must show a minimum of 3 years of experience in the work classification, or an equivalent acceptable to the board. Question 4: Which of the following identifies the “Contractor of Record” on a service invoice in Michigan?
- A) Company phone number only
- B) License number and classification
Explanation: The provisions of the International Mechanical Code, 2021 edition, as amended by the Michigan Administrative Code, govern. Question 7: Which classification of contractor license includes “Refrigeration” as a specific work category in Michigan?
- A) Only “Unlimited Service”
- B) Only “Hydronic Heating”
- C) Both “Limited Refrigeration” and “Unlimited Refrigeration and Air Conditioning Service”
- D) “Ductwork” only Answer: C Explanation: Michigan licenses include both “Limited service, heating or refrigeration” and “Unlimited service, heating or refrigeration” as specific classifications. Question 8: What is the scope of work for the Michigan Unlimited Refrigeration & Air Conditioning Service license?
- A) Only residential split systems up to 5 tons
- B) Diagnosis and servicing of refrigeration and air conditioning equipment employing the refrigeration cycle, unlimited as to thermal capacity or type of refrigerant
- C) Only commercial freezers under 10 HP
- D) Only installation of self‑contained window units Answer: B Explanation: The scope includes diagnosing and servicing refrigeration and air conditioning equipment that uses the refrigeration cycle, with no limits on thermal capacity or refrigerant type, including ammonia and flammable refrigerants.
Question 9: A refrigeration contractor relocates their main office. Within how many days must they notify the Bureau of Construction Codes of their new address?
- A) 10 days
- B) 30 days
- C) 60 days
- D) 90 days Answer: B Explanation: Michigan licensing regulations require licensees to update their contact information with the Bureau of Construction Codes within 30 days of a change. Question 10: Which national code does the Michigan Mechanical Code (MMC) primarily adopt and amend for statewide use?
- A) National Electrical Code (NEC)
- B) International Mechanical Code (IMC)
- C) Uniform Mechanical Code (UMC)
- D) International Building Code (IBC) Answer: B Explanation: The Michigan Mechanical Code adopts and amends the International Mechanical Code (IMC) as the primary standard for mechanical installations in the state. Question 11: Which type of mechanical work does not require a permit under Michigan law?
- A) Installing a new furnace
- B) Replacing a compressor in a walk‑in freezer
- C) Adding a new evaporator coil to an existing system
- D) Replacing a broken fan belt on an existing system
Question 14: Under Michigan’s Skilled Trades Regulation Act, how often must a mechanical contractor license be renewed?
- A) Annually
- B) Every 2 years
- C) Every 3 years
- D) Every 5 years Answer: B Explanation: Michigan mechanical contractor licenses require renewal biennially (every two years). Question 15: What is the maximum penalty for performing HVAC work without a required Michigan contractor license?
- A) A warning for first offense
- B) $1,000 fine
- C) Up to $5,000 fine plus potential imprisonment and restriction from future licensing
- D) No penalty for first offense Answer: C Explanation: Unlicensed mechanical contracting can result in significant civil fines and, in some cases, criminal penalties, along with restrictions on future licensing.
Domain 2: EPA Section 608 Regulations
Question 16: What is the maximum allowable leak rate for appliances containing 50 or more pounds of refrigerant in commercial refrigeration before repairs are mandatory?
- A) 10% per year
- B) 15% per year
- C) 20% per year
- D) 30% per year Answer: C Explanation: Under EPA Section 608, commercial refrigeration appliances with a full charge of 50+ lbs of refrigerant must be repaired when the leak rate exceeds 20% of the full charge annually. Question 17: Which of the following refrigerants is prohibited from being intentionally vented under any circumstances?
- A) R-134a
- B) R-410A
- C) R- 22
- D) All of the above Answer: D Explanation: EPA regulations prohibit the intentional venting of all CFC, HCFC, and HFC refrigerants. Venting is only allowed for “de minimis” releases during good-faith servicing. Question 18: What is the maximum system-dependent recovery equipment charge for a Type I appliance?
- A) 10 lbs
- B) 15 lbs
- C) 20 lbs
Question 21: Which EPA regulation specifically prohibits the use of R-22 in new HVAC equipment manufactured after January 1, 2010?
- A) Clean Air Act Title VI
- B) Montreal Protocol
- C) Section 608 of the Clean Air Act
- D) All of the above Answer: A Explanation: The U.S. Clean Air Act Title VI bans the manufacture of R-22 equipment after 2010, in alignment with the Montreal Protocol. Question 22: What is the required evacuation level for a recovery cylinder before it can be sent for recycling?
- A) 0 psig
- B) 10 inches of Hg vacuum
- C) 15 inches of Hg vacuum
- D) 1 psig positive pressure Answer: C Explanation: Recovery cylinders must be evacuated to 15 inches of Hg vacuum before being returned for recycling. Question 23: Which refrigerant is classified as an HFO with an ultra‑low GWP and is being used as a replacement for R-134a?
- A) R-1234yf
- B) R- 22
- C) R-410A
- D) R-404A
Answer: A Explanation: R‑1234yf is an HFO (hydrofluoroolefin) refrigerant with a GWP of less than 1, commonly used as a replacement for R‑134a in automotive and some stationary systems. Question 24: A technician performing a repair on a high-pressure system containing 200 lbs of R-410A must repair any leak exceeding what percentage of the full charge?
- A) 10%
- B) 15%
- C) 30%
- D) 40% Answer: B Explanation: For high-pressure appliances (comfort cooling) with a full charge of 200+ lbs, the mandatory repair threshold is 15% of the full charge annually. Question 25: Which is a violation of EPA regulations?
- A) Recovering refrigerant into a non‑refillable cylinder and then refilling it
- B) Transporting a recovery cylinder without a label
- C) Using a recovery machine that is not certified
- D) All of the above Answer: D Explanation: All listed actions violate EPA Section 608 regulations.
Answer: C Explanation: R‑404A has a GWP of approximately 3,900, one of the highest among common HFC refrigerants, leading to phasedown regulations. Question 29: Who is eligible to purchase R-22 after the January 1, 2020 production ban?
- A) Anyone with a valid EPA Section 608 certification
- B) Only technicians working on systems grandfathered to use R- 22
- C) Only manufacturers of new R-22 equipment
- D) No one; R-22 can no longer be produced or imported Answer: D Explanation: The production and import of R‑22 were banned as of January 1, 2020. Existing supplies can be used only from previously produced stocks. Question 30: What action must a technician take when replacing a compressor on a system with 150 lbs of R-134a that is discovered to be leaking 25% of the full charge per year?
- A) Perform the repair without any leak repair requirement
- B) Notify the EPA of the leak within 48 hours
- C) Repair the leak within 30 days or retrofit/retire the appliance
- D) Replace the entire system regardless of leak severity Answer: C Explanation: Appliance owners/operators have 30 days to repair a leak above the threshold (commercial refrigeration: 20%) or retrofit/retire the appliance.
Domain 3: Refrigeration Cycle & Components Question 31: What is the primary function of a compressor in a vapor compression refrigeration system?
- A) To add heat to the refrigerant
- B) To remove heat from the refrigerant
- C) To increase the pressure and temperature of the refrigerant vapor
- D) To decrease the pressure of the liquid refrigerant Answer: C Explanation: The compressor takes low‑pressure, low‑temperature refrigerant vapor and compresses it to high‑pressure, high‑temperature superheated vapor. Question 32: In a vapor compression cycle, which component rejects heat from the refrigerant to the outside environment?
- A) Evaporator
- B) Compressor
- C) Condenser
- D) Expansion valve Answer: C Explanation: The condenser rejects heat from the high‑pressure superheated vapor, condensing it into a high‑pressure liquid as heat is transferred to the ambient air or water. Question 33: What is the typical state of the refrigerant entering the expansion device?
- A) Low‑pressure liquid–vapor mixture
Question 36: What is subcooling?
- A) The heat removed from a liquid below its saturation temperature
- B) The heat added to a vapor above its saturation temperature
- C) The pressure difference across the expansion valve
- D) The volume of refrigerant in the system Answer: A Explanation: Subcooling is the temperature difference between the liquid’s actual temperature and its saturation temperature at the same pressure, measured at the condenser outlet. Question 37: Which compressor type is positive displacement and uses a rotating shaft with one or more vanes that slide in and out as the shaft rotates?
- A) Reciprocating
- B) Scroll
- C) Rotary vane
- D) Centrifugal Answer: C Explanation: A rotary vane compressor uses sliding vanes that trap and compress refrigerant between the cylinder wall and the rotor, common in small hermetic applications. Question 38: What is the primary advantage of a scroll compressor over a reciprocating compressor in residential and light commercial systems?
- A) Higher compression ratio capability
- B) Lower cost and simpler manufacturing
- C) Fewer moving parts, quieter operation, and higher efficiency
- D) Only operates at a fixed speed Answer: C Explanation: Scroll compressors have fewer moving parts, lower vibration, higher isentropic efficiency, and generally quieter operation than reciprocating compressors of equivalent size. Question 39: Which type of expansion device responds to changes in superheat to regulate refrigerant flow into the evaporator?
- A) Fixed orifice / piston
- B) Capillary tube
- C) Thermostatic expansion valve (TXV)
- D) Electronic expansion valve (EEV) (requires electronic control, but still responds to superheat) Answer: C Explanation: A TXV uses a bulb attached to the evaporator outlet to sense temperature and a pressure port to sense evaporator pressure, modulating the valve to maintain constant superheat. Question 40: A system has been diagnosed with a leaking evaporator coil. After the repair, nitrogen is used for a pressure test. What is the typical safe pressure for a nitrogen leak test on a low-pressure R-22 system?
- A) 2–5 psig
- B) 10–15 psig
- C) 150 psig (design pressure of the low side)
- D) 400 psig Answer: C
- D) Non‑condensables in the system Answer: B Explanation: An overcharge forces more liquid into the condenser, increasing subcooling and flooding the evaporator (low superheat). Question 44: What is the likely cause of low suction pressure and low discharge pressure?
- A) Overcharge of refrigerant
- B) Undercharge of refrigerant
- C) Restriction in the liquid line or filter‑drier
- D) Restriction on the discharge line Answer: B Explanation: An undercharge of refrigerant reduces the mass flow through the system, lowering both suction and discharge pressures. Question 45: What type of compressor is considered non‑positive displacement?
- A) Reciprocating
- B) Scroll
- C) Screw
- D) Centrifugal Answer: D Explanation: Centrifugal compressors are non‑positive displacement; they use a spinning impeller to increase pressure by converting velocity head into pressure head.
Question 46: In a split‑system residential air conditioner, where is the metering device typically located?
- A) Outdoor unit near the service valves
- B) Indoor unit at the evaporator inlet
- C) On the discharge line of the compressor
- D) On the liquid line leaving the condenser Answer: B Explanation: The metering device is located at the evaporator inlet, either as a TXV (indoor unit) or a piston in the indoor coil distributor. Question 47: The compressor motor windings short to ground. What is the appropriate next step for the service technician after confirming the short?
- A) Replace only the compressor
- B) Replace the compressor and install a new filter‑drier and suction line filter, then acid test and flush the system
- C) Add a hard start kit to bypass the short
- D) Add refrigerant to cover the short Answer: B Explanation: A compressor burnout (acid formation) requires replacement of the compressor, installation of suction and liquid line filter‑driers, acid testing, and system flushing. Question 48: What is the function of a crankcase heater on a compressor?
- A) To heat the oil for better flow
- B) To prevent liquid refrigerant migration to the crankcase during off‑cycles
- C) To increase discharge temperature
