Exam Cheat Sheet · Quick Reference
South Carolina - Refrigeration
South Carolina · PSI Services Contractor
Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
50
Passing score
70%
Exam time
180 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
South Carolina State Portion 50 questions
Code Compliance
7 Q · 14%
Permit requirements, application procedures, and feesInspections and testing requirements for mechanical systemsAuthority and duties of the code officialRefrigerant classification, allowable quantities, and occupancy restrictionsMachinery room construction and ventilation requirementsRefrigerant piping materials, joints, and installation standardsEquipment listing, labeling, and approval requirementsOSHA general safety and health provisions for construction contractorsExhaust SystemsDuct SystemsRefrigerationDefinitions
+1 more
HARV General
11 Q · 22%
Compression refrigeration cycle components and operationRefrigerant classification, properties, and environmental impact (ODP, GWP, Clean Air Act)Refrigerant handling equipment: cylinders, gauge manifolds, service valves, and pressure gaugesRefrigerant recovery, recycling, reclaiming, and evacuation proceduresLeak detection methods and refrigerant charge verification (superheat and subcooling)Metering devices: capillary tubes, TXVs, AXVs, EEVs, and fixed-orifice typesHeat exchangers: evaporator and condenser types, construction, and defrost methodsRefrigerant flow components: filter-driers, sight glasses, liquid receivers, check valves, and solenoid valvesCommercial Metering Devices and ValvesElectrical Control SystemsEquipment and Instruments for Refrigerant Handling and ServiceWorking with Refrigerants
+4 more
HARV Maintenance
8 Q · 16%
Refrigerant charge verification using subcooling and superheat methodsRefrigerant recovery procedures (passive and active methods)System evacuation and leak detection techniquesCompressor inspection and testing (hermetic and open-drive)Filter-drier and sight glass inspection and replacementElectrical component testing using voltmeters, ammeters, and ohmmetersCondenser and evaporator cleaning and maintenanceMotor lubrication, belt tension, and bearing inspectionCommercial Metering Devices and ValvesTroubleshooting Commercial Systems—System DiagnosisElectrical Control SystemsInstallation and Service of Domestic Refrigerators and Freezers
+2 more
HARV Controls
8 Q · 16%
Thermostat sensing elements and switching devices (bimetal strips, thermistors, mercury switches, reed switches)Heat and cooling anticipators (operation, adjustment, and effect on system overshoot and lag)Thermostat types by voltage class (line-voltage, low-voltage 24 Vac, millivolt)Thermostat terminal identification and wiring conventions (R, W, Y, G, C, O/B terminals)Programmable and digital thermostat features (scheduling, override, wireless/Wi-Fi, power-stealing)Zoned system controls (zone control panels, damper types, bypass dampers, master-slave thermostats)Thermostat diagnostics and troubleshooting procedures (voltage measurements, jumper tests, multistage systems)Control system range and differential adjustment (cut-in, cut-out, set point effects on run time and cycle interval)Electrical Control SystemsCommercial Air-Conditioning ControlsElectric MotorsServicing Electric Motors and Controls
+1 more
Piping - General
3 Q · 6%
Types of refrigerant tubing and pipe (ACR copper, stainless steel, aluminum)Non-refrigerant piping materials (copper water tubing, plastic pipe, steel pipe)Tubing cutting, reaming, and bending proceduresFlared, soldered, brazed, and swaged tubing connectionsPipe joining methods (threaded, solvent-cemented, welded, mechanical joints)Hydronic piping materials standards and fitting requirementsFuel oil piping materials, joints, and installation requirementsPipe support spacing and hanger requirementsFull TextCommercial Metering Devices and Valves
Piping - Dimensioning and Design
9 Q · 18%
Pipe and tubing dimensions by material type (copper ACR, Type K/L/M, steel schedules, plastic)Setback and length of bend calculations for standard angles (15° through 180°)Offset bend calculations (travel, run, and offset relationships)Fitting laying lengths and center-to-end dimensions for elbows, tees, and reducersPipe support spacing requirements based on pipe material, size, and temperatureHydronic piping material standards and approved joint types per SC Mechanical CodePipe expansion allowances and thermal compensation methodsMinimum bending radius requirements for tubing and pipeFull TextWorking with Tubing and Piping
Safety
4 Q · 8%
Lockout/tagout (LOTO) procedures for electrical and mechanical systemsPersonal protective equipment (PPE) selection and requirementsRefrigerant, chemical, and breathing hazards identificationFire hazards, fire extinguisher classes, and fire preventionFall protection systems and requirements (guardrails, safety nets, personal fall arrest)Confined space entry requirements and permit proceduresSC 811 excavation notification requirements, locate requests, and excavator responsibilitiesHazard communication, safety data sheets (SDS), and toxic/hazardous substance exposure limitsSubpart D-Occupational Health and Environmental ControlsSubpart Z—Toxic and Hazardous Substances
Key Distinctions
Single screw compressorvsTwin screw compressor
A single screw compressor uses one main rotor that meshes with two star-shaped rotors driven by the main rotor, while the basic operating principles are the same as other screw compressors.
Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.2.4 — Single Screw CompressorSoldered joints on refrigerant pipingvsBrazed, welded, flared, mechanical or press-connect joints
Soldered joints (cleaned, ASTM B813 flux, ASTM B32 solder) are permitted only on Group A1 refrigerant systems at pressures less than or equal to 200 psi (1378 kPa); higher pressures or other safety groups require brazed, welded, flared, mechanical or press-connect joints.
SC Mechanical Code 2021, Chapter 11 — Section 1108.3.3 Soldered JointsSuperheatvsSubcooling
Superheat is the low-side value found by subtracting suction saturation temperature from measured suction-line temperature (used to adjust the TXV), while subcooling is the high-side value found by subtracting liquid-line temperature from condensing (discharge) saturation temperature.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 108Range adjustment on a low-pressure motor controlvsDifferential adjustment on a low-pressure motor control
The range screw moves both cut-in and cut-out an equal amount (clockwise/in raises both, counterclockwise/out lowers both), while the differential adjustment affects only the cut-out pressure (clockwise raises cut-out); always confirm direction with the manufacturer's instructions since some units reverse it.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 333Condenser pressure regulator (ORI)vsReceiver pressure regulator (ORD)
The condenser pressure regulator sits at the condenser outlet and closes in cold weather, while the receiver pressure regulator is an open-on-rise-of-differential valve piped from the discharge line to the receiver that opens at a discharge-to-receiver difference usually between 20 and 30 psi to bypass hot gas into the receiver.
Modern Refrigeration and Air Conditioning (22nd ed.), Pages 1118-1119High-pressure motor controlvsLow-pressure motor control
The high-pressure control is a safety device usually set to cut out at 20% above normal head pressure, while the low-pressure control is the normal cycling control whose cut-in/cut-out difference varies by refrigerant (about 20 psi for R-401A and R-404A, 16 psi for R-134a).
Modern Refrigeration and Air Conditioning (22nd ed.), Page 334Magnetic overload devicevsThermal/bimetal overload
A magnetic overload is a normally closed device in series with the start winding that opens when start-winding current exceeds the motor's full locked rotor amps (responding to the magnetic field of current), whereas thermal and bimetal overloads respond to ambient or motor heat and can nuisance-trip in hot locations.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 350Power-open/power-closed damper motorvsTwo-wire normally open or normally closed (spring-return) damper
Power-open/power-closed dampers have three to five wires and require an end switch premounted on the motor that actuates at the closed position, while two-wire normally open/normally closed dampers use a return spring instead.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 571Pressure lubrication systemvsSplash lubrication system
A pressure system uses an oil pump to force oil to all bearing surfaces so the compressor runs quieter even with greater bearing clearances, because the pressurized oil film cushions the bearings; a splash system has no pressurized oil cushion.
Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.3.4 — Pressure LubricationSwing check valvesvsLift check valves
The safe selection rule is swing checks with gate valves (straight-way flow as in gate valves) and lift checks with globe and angle valves (lift check design requires a change in flow direction, as in globe valves).
Pipefitter's Handbook (3rd ed.), Chapter 1 (Full Text), Check Valves — Service CharacteristicsSplit or double disc gate valvevsSolid wedge gate valve
The split/double disc type should be installed with the stem vertical and handwheel up to guard against jamming of the disc spreader mechanism, while the solid wedge type can be installed in any position without danger of the disc jamming.
Pipefitter's Handbook (3rd ed.), Chapter 1 (Full Text), Gate Valves — Service CharacteristicsCopper tubing support spacing tablevsSchedule 40 pipe support spacing table
Copper tubing support spacing is indexed by tube outside diameter while Schedule 40 pipe spacing is indexed by nominal pipe size; since copper tube OD equals nominal size plus 1/8 in., using the wrong column shifts spacing one size.
Piping Design – General, Chapter 1 — Tables 7 and 8, Recommended Support SpacingSmoke detectors in return air risersvsSmoke detectors in a return air duct or plenum
Per SC Mechanical Code 2021 Section 606.2.3, risers serving two or more stories and any portion of a return system with design capacity greater than 15,000 cfm need detectors at each story, while the 2,000 cfm threshold of Section 606.2.1 applies to the return air duct or plenum.
SC Mechanical Code 2021, Chapter 6 Duct Systems — Section 606.2.3 Return Air RisersKey Terms
Pressure Vessels—Refrigerant (SC Mechanical Code 2021, Ch. 2) SC Mechanical Code 2021, Chapter 2 Definitions — Pressure Vessels—Refrigerant
Any refrigerant-containing receptacle in a refrigerating system, excluding evaporators where each separate section does not exceed 0.5 cubic foot (0.014 m³) of refrigerant-containing volume regardless of maximum inside dimensions, and excluding evaporator coils, controls, headers, pumps and piping.
Competent person (29 CFR 1926.32(f)) OSHA 1926 CFR 29, Page 31
One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them (no specific degree, experience, or certificate required).
Tolerance Zone (SC Code §58-36-20(21)(a)) SC 811 Excavator Manual (2024), Pages 28 and 46
When the facility diameter is known, the zone extending one-half of the known diameter plus twenty-four inches on either side of the designated center line of the underground facility.
Refrigeration machinery room normal ventilation (SC Mechanical Code 1105.6.3.1) SC Mechanical Code 2021, Chapter 11 — Section 1105.6.3.1 Quantity—Normal Ventilation
During occupied conditions the exhaust must be the larger of 0.5 cfm per square foot of room area or 20 cfm per person, and the volume needed to limit room temperature rise to 18°F.
Refrigerant safety group (ASHRAE Standard 34) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 2 — Refrigerants as Hazards section (Page 22)
A classification where the letter shows toxicity (A = lower, B = higher) and the number shows flammability (1 = none, 2 = low, 2L = low with slow burn velocity, 3 = high), so a B1 refrigerant is higher toxicity with no flammability.
Megohmmeter (electrical insulation tester) Modern Refrigeration and Air Conditioning (22nd ed.), Page 365 — Section 18.1.7 Electrical Insulation Testers
An instrument that applies its own known voltage — usually between 500 Vdc and 1000 Vdc — to read insulation resistance in the megohm range, to be used only by an experienced technician because prolonged application can further weaken or damage windings and insulation.
Hermetic compressor insulation test hookup Modern Refrigeration and Air Conditioning (22nd ed.), Page 366
With power off and all wires removed, jumper all compressor terminals together, place the black lead on a clean bare spot on the dome and the red lead on one motor terminal so only winding-insulation-to-ground resistance is measured.
Receiver pressure regulator (ORD valve) Modern Refrigeration and Air Conditioning (22nd ed.), Pages 1118-1119
An open-on-rise-of-differential-pressure valve that bypasses hot gas from the discharge line into the liquid receiver, with a pressure-difference setting usually between 20 and 30 psi, to restore head pressure in low ambient so the TXV keeps feeding the evaporator.
Crankcase pressure regulator (CPR) Modern Refrigeration and Air Conditioning (22nd ed.), Pages 1109 to 1110
A suction-line regulator ahead of the compressor, field-set with its calibration screw according to the rated load amperage (RLA) of the compressor motor, that throttles suction vapor so motor current stays below electrical overload during hot pull-down and after defrost.
Multipurpose fuse Modern Refrigeration and Air Conditioning (22nd ed.), Page 347
A fuse combining fast-acting and time-delay characteristics that tolerates small, short-duration overloads such as motor starting but blows immediately when the overload exceeds 500% of its maximum current rating.
Magnetic overload device Modern Refrigeration and Air Conditioning (22nd ed.), Page 350
A normally closed device wired in series with the motor start winding that opens when sensed start-winding current exceeds the full locked rotor amps of the motor.
Clearance space (reciprocating compressor) Modern Refrigeration and Air Conditioning (20th ed.), Chapter 18, Section 18.2.1 — Clearance Space
The small volume between the piston at top dead center and the valve plate, approximately 0.010″ to 0.020″ (.254 mm to .508 mm).
End switch (zone damper) Modern Refrigeration and Air Conditioning (22nd ed.), Page 571
A switch premounted on a power-open/power-closed damper motor that actuates when the damper reaches the closed position; wired in series it interrupts motor current at the correct position, or on some building-automation dampers closes to signal the controller.
Single phasing of a three-phase motor Modern Refrigeration and Air Conditioning (22nd ed.), Page 384 — Section 19.1.2 Single Phasing of Three-Phase Motors
Loss of one supply phase that forces the two remaining sets of windings to carry the entire load at 1½ times normal full-load current, quickly overheating the motor unless a phase loss monitor opens the control circuit.
DDC resistance-type input signal Modern Refrigeration and Air Conditioning (22nd ed.), Page 579
The standard resistance input range for DDC input devices is 0–135 ohms; other standard DDC input signals are 4–20 mA, 0–5 Vdc and 0–10 Vdc, and millivolt (mV).
Motor internal temperature estimate Modern Refrigeration and Air Conditioning (22nd ed.), Page 384 — Section 19.1.1 Motor Temperature
A motor's internal temperature is typically about 20°F (11°C) higher than the motor frame temperature, and by a separate rule the hottest part inside a motor should not exceed 72°F above ambient.
Dwelling-unit whole-house ventilation reduction (SC Mechanical Code 403.3.2.1, Exception 2) SC Mechanical Code 2021, Chapter 4 Ventilation — Section 403.3.2.1 Outdoor Air for Dwelling Units, Exception 2
The minimum ventilation rate from Equation 4-9 may be reduced by 30 percent only when both a ducted system supplies ventilation air directly to each bedroom and to one or more of the living room, dining room or kitchen, and the whole-house system is balanced.
Safety net drop test (29 CFR 1926.502(c)(4)(i)) OSHA 29 CFR 1926, §1926.502(c)(4)(i)
Nets and net installations must be drop-tested at the jobsite after initial installation and before use, whenever relocated, after major repair, and at 6-month intervals if left in one place; the weekly inspection for wear and damage is a separate requirement.
Formulas to Know
Evaporator superheat and subcooling
Superheat = suction line temp at evaporator outlet − suction saturation temp (example: 32°F − 20°F = 12°F); Subcooling = discharge saturation temp − liquid line temp at condenser outlet (example: 100°F − 85°F = 15°F)High-pressure safety cut-out setting
Cut-out = 1.20 × normal head pressure (20% above normal); examples: 250 psig × 1.20 = 300 psig; 230 psig × 1.20 = 276 psigLow-pressure control cut-out from cut-in and differential
Cut-out = cut-in − differential (example: 60 psig − 35 psig = 25 psig); operating range/span runs from cut-out to cut-in; widening the differential lengthens the off cycleBranch-circuit voltage drop and acceptable voltage band
VD = (2 × L × R × I) ÷ 1000 (example: 2 × 250 ft × 3.19 Ω/1000 ft × 8 A ÷ 1000 = 12.76 V, leaving 107.2 V); most HVACR equipment must operate within ±10% of rated voltage (120 V → 108–132 V; 230 V → minimum 207 V)OSHA lead exposure limit for shifts longer than 8 hours (29 CFR 1926.62(c)(2))
Allowable exposure (µg/m³) = 400 ÷ hours worked in the day (10-hour shift: 400 ÷ 10 = 40 µg/m³); the 8-hour TWA PEL is 50 µg/m³ and the action level is 30 µg/m³Refrigeration machinery room occupied exhaust airflow
Exhaust = larger of (0.5 cfm/ft² of room area or 20 cfm/person) and the volume limiting room temperature rise to 18°F (example: 400 ft² × 0.5 = 200 cfm vs 4 persons × 20 = 80 cfm → 200 cfm governs)Length of pipe in a bend (centerline) and bend setback
Arc length = degrees × .01745 × radius (60° multiplier 1.047: 12 in. × 1.047 = 12 9/16 in.; 90° = R × 1.571; 120° = R × 2.094); total 180° of bend = Radius × 3.1416 regardless of how the bend is divided (10 in. × 3.1416 ≈ 31-7/16 in.); 150° setback = Radius × 3.73 (135° = 2.41, 120° = 1.732)3-piece 90° welded turn dimensions
A (center-to-end of each end piece) = Radius × .4142; B = 2A = Radius × .828 (18 in. radius: A = 7 7/16 in., B = 14 7/8 in.); for a 4-piece 90° turn A = Radius × .2679Motor branch-circuit protection and overload setting
Dual-element (time-delay) fuse maximum = 175% of table full-load current (22 A × 1.75 = 38.5 A); inverse-time breaker maximum = 250% of table FLC (22 A × 2.50 = 55.0 A; 27 A × 2.50 = 67.5 A); overload relay for service factor 1.00 set at 115% of NAMEPLATE FLA (4.6 A × 1.15 = 5.3 A)Single-phasing current and mixed-air temperature
Single phasing: each remaining winding set carries 1.5 × full-load amps (18 A × 1.5 = 27 A). Mixed air: T_mix = (Return CFM × Return Temp + Outdoor CFM × Outdoor Temp) ÷ Total CFM (example: (3,000 × 60 + 1,000 × 92) ÷ 4,000 = 68.0°F; outdoor-air fraction = 1,000 ÷ 4,000 = 25%)