South Carolina Refrigeration Contractor Examination

Under the 2021 International Mechanical Code (IMC), when the quantity of refrigerant in an independent circuit exceeds the amount in Table 1103.1, refrigerant-containing components shall be located:

• AIn any mechanical closet that has a louvered door to the occupied space
• BEither outdoors or in a machinery room constructed to Chapter 11
• CIn the smallest occupied space served by the system
• DAbove a suspended ceiling used as a return-air plenum

A listed, factory-built condensing unit contains 5.5 lb of refrigerant. Does the 2021 IMC require a machinery room solely because of that charge?

• AYes, any charge over 3 lb requires a machinery room
• BYes, unless the refrigerant is Group A1
• CNo, listed equipment with not more than 6.6 lb is exempt regardless of safety group when…
• DNo, because machinery rooms are required only for ammonia

A new industrial refrigeration plant will use R-717 (ammonia). Which standards govern that system under the 2021 IMC?

• AIMC Chapter 11 in full, because ammonia is listed in Table 1103.1
• BIIAR 2, IIAR 3, IIAR 4, and IIAR 5; the system is not required to comply with IMC Chapter…
• CASHRAE 15 only, with no IIAR documents
• DThe International Fuel Gas Code, because ammonia is treated as a fuel gas

A supermarket rack with 280 lb of Group A1 refrigerant will be converted to a different A1 blend. What does IMC 1101.7 require before the refrigerant type is changed?

• ANo notice is required if both refrigerants are Group A1
• BPrior notification to the code official and compliance with the provisions that apply to…
• COnly a manufacturer letter left in the equipment packet
• DApproval from EPA Section 609 instead of the building official

Outdoor refrigerant circuit access ports on a rooftop condensing unit that is reachable from an unlocked stair and ladder must be:

• ALeft with standard plastic Schrader caps so gauges can be connected quickly
• BFitted with locking-type tamper-resistant caps or otherwise secured against unauthorized…
• CRemoved and the ports brazed shut after startup
• DPainted red and labeled only, without a locking cap

In an institutional occupancy (other than a kitchen, laboratory, or mortuary), how does the 2021 IMC treat the Table 1103.1 refrigerant quantities?

• AThe table amounts are doubled because staff are always present
• BThe table amounts are reduced by 50 percent, and the total of all Group A2, B2, A3, and B…
• CInstitutional occupancies may use unlimited A1 refrigerant but no flammable refrigerant
• DOnly ammonia is restricted; all fluorinated refrigerants use the unreduced table

A technician wants to add a few pounds of a different ASHRAE 34 refrigerant blend into an existing circuit to 'top it off.' What does IMC 1102.2.1 require?

• AAny A1 refrigerants may be mixed freely
• BRefrigerants with different ASHRAE 34 designations shall not be mixed, except where the e…
• CMixing is allowed if the blend GWP is lower than the original charge
• DMixing is allowed after the system is evacuated to 500 microns

Recovered refrigerant may be reused in which of the following situations under IMC 1102.2.2.2, provided it is filtered and dried and is not clearly contaminated?

• AIn any owner's equipment as long as the ASHRAE 34 designation matches
• BOnly in the system from which it was recovered or in other systems of the same owner
• COnly after it is sold through a wholesaler as new product
• DIn a different owner's system if a sight glass shows a clear liquid

Which refrigeration system type is classified as a high-probability system under IMC 1103.3?

• AA double-indirect open-spray system with isolated refrigerant piping
• BAn indirect closed (chiller) system with the refrigerant confined to the machine room
• CA direct system in which the evaporator is in the occupied airstream
• DAn indirect-vented closed system

A 20 ft by 25 ft refrigeration machinery room is occupied by two technicians. What minimum normal mechanical exhaust rate does IMC 1105.6.3.1 require based on the area/person rules (ignoring the separate 18°F temperature-rise check)?

• A40 cfm (20 cfm per person)
• B250 cfm (0.5 cfm per square foot)
• C500 cfm (1.0 cfm per square foot)
• D100 cfm (flat machinery-room minimum)

Mechanical exhaust from a refrigeration machinery room shall discharge to the outdoors not less than how far from a property line or openings into buildings?

• A5 feet
• B10 feet
• C20 feet
• D50 feet

In an A2L machinery room that uses the IMC 1106.4 ventilation alternative instead of Class I, Division 2 wiring, refrigerant detectors shall activate at or below what concentration?

• AThe refrigerant's occupational exposure limit (OEL) only
• B25 percent of the lower flammability limit (LFL)
• C50 percent of the LFL
• D100 percent of the LFL

IMC 1106.5 requires clearly identified break-glass (or approved tamper-resistant) remote switches for a machinery room. Which pairing is correct?

• AOn-only control of compressors and off-only control of ventilation fans
• BOff-only control of refrigerant compressors, refrigerant pumps, and normally closed autom…
• COn/off maintained switches for both the refrigeration plant and the fans
• DA single switch that starts the compressors and stops the fans together

Ducts and air handlers in a machinery room that operate at a lower pressure than the room shall be:

• ALeft open so the room can use them as makeup air
• BSealed to prevent refrigerant leakage from entering the airstream
• CFitted only with a smoke detector
• DInterlocked to shut down when the compressor starts

In a vapor-compression refrigeration cycle, which component absorbs heat from the refrigerated space or product?

• AThe condenser
• BThe compressor
• CThe evaporator
• DThe liquid receiver

What is the primary function of the compressor in a mechanical refrigeration system?

• ATo store surplus liquid refrigerant
• BTo raise the pressure and temperature of the refrigerant vapor so heat can be rejected at…
• CTo meter liquid into the evaporator at constant enthalpy
• DTo separate oil from liquid refrigerant in the liquid line

As refrigerant passes through a thermostatic expansion valve or other throttling device, which change occurs?

• APressure and temperature both drop, and a portion of the liquid flashes to vapor
• BPressure rises while temperature stays constant
• CEnthalpy increases by the compressor work input
• DThe refrigerant becomes a subcooled liquid at condenser pressure

Superheat is best defined as:

• AThe number of degrees the refrigerant vapor is above its saturation temperature at the me…
• BThe number of degrees the liquid is below its saturation temperature
• CThe temperature difference between the refrigerated box and the condenser air
• DThe heat added by the compressor motor only

Subcooling is best defined as:

• ACooling the suction vapor below the box temperature
• BThe number of degrees the liquid refrigerant is below its saturation temperature at the m…
• CAny temperature below 32°F
• DThe temperature drop across the evaporator coil face

A technician measures 76 psig suction pressure on an R-404A medium-temperature case. The P/T chart saturation temperature at 76 psig is 20°F. The suction-line temperature at the evaporator outlet is 32°F. What is the evaporator superheat?

• A12°F
• B20°F
• C32°F
• D52°F

Liquid-line pressure on an R-134a system converts to a saturation temperature of 110°F. The liquid-line temperature leaving the condenser is 98°F. What is the condenser subcooling?

• A8°F
• B12°F
• C98°F
• D208°F

Evaporator temperature difference (TD) for a refrigerated fixture is:

• ABox (or entering-air) temperature minus evaporator saturation temperature
• BCondenser saturation temperature minus outdoor air temperature
• CDischarge line temperature minus liquid-line temperature
• DSuperheat plus subcooling

A walk-in cooler is holding 38°F. Evaporator saturation temperature is 23°F. What is the evaporator TD, and what is a typical design implication?

• A15°F TD, a common medium-temperature DX selection that provides both capacity and some de…
• B38°F TD, which is the design target for all coolers
• C23°F TD, which indicates a flooded evaporator
• D61°F TD, which is required to prevent coil icing

A TXV system shows unusually high evaporator superheat, low suction pressure, and a warm suction line. The most likely cause is:

• AOvercharge or a TXV that is overfeeding
• BUndercharge, a liquid-line restriction, or a TXV that is underfeeding
• CA dirty condenser only, with a correct charge
• DA failed crankcase heater on an idle compressor

Low or zero evaporator superheat on a running DX system most nearly indicates:

• AThe evaporator is overfed or the system is overcharged, with liquid leaving the coil
• BThe system is undercharged
• CThe filter-drier is completely plugged
• DThe condenser fan has failed

A TXV condensing unit has high head pressure, high subcooling, and a full sight glass. The most likely charge-related diagnosis is:

• AUndercharge
• BOvercharge
• CNoncondensable air with a critically low charge
• DA starved TXV from a restricted drier

One refrigeration ton is defined as:

• A1,000 Btu/h
• B12,000 Btu/h
• C120,000 Btu/h
• DThe weight of 2,000 lb of ice

A walk-in freezer evaporator is rated to absorb 96,000 Btu/h at the design TD. What is that capacity in refrigeration tons?

• A4 tons
• B8 tons
• C12 tons
• D96 tons

Which compressor lubricant is generally required for HFC and HFO refrigerants such as R-404A, R-134a, and R-448A?

• ANaphthenic mineral oil, because it is fully miscible with all HFCs
• BPolyolester (POE) oil, which is hygroscopic and miscible with HFC/HFO refrigerants
• CAlkylbenzene only, with no POE allowed
• DAutomotive PAG oil from motor-vehicle systems

A liquid receiver is primarily used to:

• AStore high-pressure liquid refrigerant and allow the system to pump down
• BPrevent liquid from entering the compressor suction
• CSeparate oil from discharge vapor
• DMeter refrigerant into the evaporator

Where is a suction-line accumulator installed, and what is its purpose?

• AIn the liquid line, to store spare charge
• BIn the suction line, to trap liquid refrigerant and oil and return them to the compressor…
• COn the condenser outlet, to increase subcooling
• DOn the discharge line, to knock out oil before the condenser

Flash gas in a liquid line just ahead of a TXV is undesirable because it:

• AIncreases liquid subcooling and capacity
• BReduces mass flow through the metering device and starves the evaporator
• CAlways indicates a failed compressor valve plate
• DIs required for proper TXV bulb response

In the direction of refrigerant flow, the four basic vapor-compression components are:

• ACompressor, evaporator, condenser, expansion device
• BCompressor, condenser, expansion device, evaporator
• CEvaporator, condenser, compressor, expansion device
• DReceiver, compressor, TXV, condenser

Heat rejected at the condenser is approximately equal to:

• AOnly the compressor motor heat
• BThe evaporator refrigerating effect plus the heat of compression
• COnly the latent heat of the refrigerated product
• DThe evaporator load minus compressor work

A condensing unit nameplate charge is 16 lb 0 oz, which includes a 15 ft line set. The installed 3/8-inch liquid line is 40 ft. The manufacturer specifies 0.60 oz of additional refrigerant per extra foot of 3/8-inch liquid line. What total charge should be weighed in?

• A16 lb 0 oz
• B16 lb 15 oz
• C17 lb 0 oz
• D25 lb 0 oz

Compared with a direct-expansion (DX) evaporator, a flooded evaporator typically:

• AFeeds only superheated vapor into the coil and has no liquid present
• BMaintains a liquid level so most of the coil surface is wetted, often using a surge drum…
• CCannot be used on industrial ammonia or large halocarbon plants
• DDoes not require any level or float control

Under EPA Section 608, knowingly venting CFC, HCFC, HFC, or HFO refrigerant from a stationary system during service is:

• AAllowed if the system charge is under 50 lb
• BProhibited; refrigerant must be recovered using certified equipment
• CAllowed for HFC refrigerants only
• DAllowed if the technician holds only a Type I card

For ozone-depleting refrigerant appliances with a full charge of 50 lb or more, the EPA Section 608 annual leak-rate repair triggers are:

• A5 percent comfort cooling, 10 percent commercial refrigeration, 15 percent industrial pro…
• B10 percent comfort cooling, 20 percent commercial refrigeration, 30 percent industrial pr…
• C20 percent for every appliance type
• D50 percent for comfort cooling and 100 percent for refrigeration

A commercial refrigeration rack has a verified full charge of 200 lb. In a 3-month period the technician adds 24 lb to return it to that charge. What is the annualized leak rate, and is the 20 percent commercial-refrigeration ODS trigger exceeded?

• A12 percent; no repair trigger
• B24 percent; no repair trigger
• C48 percent; yes, the 20 percent commercial-refrigeration trigger is exceeded
• D200 percent; only industrial process rules apply

Using recovery equipment manufactured after November 15, 1993, what evacuation level does EPA require before opening a high-pressure appliance with a full charge of 200 lb or more?

• A0 inches Hg vacuum (pressure no lower than atmospheric)
• B10 inches Hg vacuum
• C25 mm Hg absolute
• D500 microns

EPA Section 608 Type II certification authorizes a technician to service:

• AOnly small appliances with 5 lb or less of refrigerant
• BHigh-pressure and very-high-pressure stationary appliances, such as split systems and sup…
• COnly low-pressure centrifugal chillers
• DOnly motor-vehicle air conditioners

Which leak-check method is allowed under EPA rules as a de minimis release?

• AReleasing the entire remaining charge to listen for hissing
• BUsing oxygen or compressed air as the test gas
• CAdding a small amount of the system refrigerant as a tracer in dry nitrogen
• DUsing propane from a torch cylinder as a tracer gas

After a system is opened and reassembled, the preferred dehydration practice before charging is to:

• ARun the compressor to pull its own vacuum
• BEvacuate with a two-stage vacuum pump to a deep vacuum (commonly 500 microns) and verify…
• CCharge immediately if the sight glass looks dry
• DPressurize with refrigerant vapor only, with no vacuum

A dirty air-cooled condenser typically produces which running symptoms?

• ALow head pressure, high suction pressure, and high capacity
• BHigh head pressure, reduced capacity, and higher compressor amperage
• CLow superheat from a flooded evaporator only
• DA deep vacuum on the suction gauge