Exam Cheat Sheet · Quick Reference
Oklahoma Refrigeration Journeyman
Oklahoma · 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
60
Passing score
70%
Exam time
150 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Oklahoma State Portion 60 questions
Electrical Knowledge and Controls
15 Q · 25%
Circuit diagrams: pictorial and ladder diagramsOhm's law, Watt's law, and power factor calculationsSingle-phase and three-phase AC motor types and starting methodsMotor starting relays: current, potential, solid-state, and PTC typesTemperature and pressure motor controls: cut-in, cut-out, range, and differential adjustmentsMotor protection devices: fuses, circuit breakers, and bimetal/thermistor overload protectionElectrical test instruments: voltmeters, ammeters, ohmmeters, multimeters, and megohmmetersTroubleshooting hermetic compressor motors and control componentsControl transformers and 24-volt control circuits
Refrigerants
5 Q · 8%
Refrigerant classification and numbering systems (CFC, HCFC, HFC, HFO, HC, inorganic series)Environmental impact of refrigerants (ODP, GWP, Montreal Protocol, Clean Air Act Section 608)Refrigerant cylinder types, color codes, and DOT regulationsPressure-temperature relationships and P/T chart interpretationRefrigerant recovery, recycling, and reclaiming procedures and equipmentEPA technician certification requirements and categories (Type I, II, III, IV)Refrigerant leak detection methods and leak repair requirementsRefrigeration lubricant types and compatibility with refrigerants
Piping
5 Q · 8%
ACR copper tubing types, sizes, and specificationsTubing cutting, reaming, and bending techniquesFlared connections: single and double flare proceduresSoldering and brazing procedures, filler metals, and fluxSwaged connections and specialized tube couplingsRefrigerant piping materials standards and approved materials (IMC 1107)Refrigerant piping installation requirements: location, identification, and protection (IMC 1109)Refrigerant piping system pressure testing and leak testing (IMC 1110)
Refrigeration Equipment and Components
17 Q · 28%
Compressor types and drive configurations (reciprocating, rotary, scroll, screw, centrifugal; open-drive vs. hermetic)Metering device types and operation (capillary tube, metering orifice, TXV, AXV, EEV, float valves)Evaporator and condenser types and construction (fin-and-tube, plate, microchannel, shell-and-tube, evaporative)Refrigerant flow control components (solenoid valves, check valves, service valves, hot-gas defrost and bypass valves)Pressure-regulating valves (CPR, EPR, relief valves, head pressure control valves)Refrigerant storage and filtration components (liquid receivers, filter-driers, sight glasses, moisture indicators)Compressor safety and protection devices (thermal overloads, discharge pressure switches, accumulators, oil separators)Evaporator defrost methods and controls (hot-gas, electric heat, off-cycle, pump-down, defrost timers)
Refrigeration Systems Operations
15 Q · 25%
Compression refrigeration cycle components and their functionsHigh-side and low-side pressure relationshipsHeat transfer principles in refrigeration (conduction, convection, radiation)Sensible heat, latent heat, superheat, and subcoolingGas laws and their application to refrigeration (Boyle's, Charles', Gay-Lussac's, combined)Pressure-temperature relationships and saturated vapor conditionsCommercial system configurations (multiple-evaporator, compound, cascade, secondary loop)Heat load calculation components (heat leakage, service load, miscellaneous loads)
Safety
3 Q · 5%
Personal protective equipment (PPE) selection and useLockout/tagout (LOTO) procedures for electrical safetyFire protection, fire extinguisher types, and the PASS methodHazard communication and Safety Data Sheets (SDS)Refrigerant, chemical, and breathing hazardsCompressed gas cylinder handling and storage for welding and cuttingConfined space entry requirements and proceduresFirst aid, medical services, and emergency action plans
Key Distinctions
ACR tubing sizingvsCopper water tubing sizing
ACR tubing is designated by its actual outside diameter, while copper water tubing nominal size equals the outside diameter minus 1/8″.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 5 - Working with Tubing and Piping, Page 71 (Section 5.1.1) (20th ed.: Chapter 8, Section 8.1.1)Galvanized steel pipevsBlack steel pipe
Galvanized pipe is treated with a zinc anticorrosion coating and is used primarily in water systems to prevent rust, while black pipe is usually less expensive and is used for gas lines and applications that do not carry water.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 5 - Working with Tubing and Piping, Page 74 (Section 5.3) (20th ed.: Chapter 8, Section 8.2.3)Hot-gas defrost valvevsHot-gas bypass valve
Both route compressor discharge gas, but the defrost valve delivers large quantities of hot gas to the evaporator to rapidly melt frost, while the bypass valve meters small amounts of hot gas to prevent compressor damage during low-load conditions.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 45 - Commercial Metering Devices and Valves, Page 1107 (Section 45.5.5) (20th ed.: Chapter 22, Sections 22.3.6 and 22.3.7 — Hot-Gas Defrost vs. Hot-Gas Bypass Valves, Pro Tip)Current relayvsPotential relay
A current relay coil is wired in series with the run winding and uses high inrush current to close normally open contacts, while a potential relay coil is wired in parallel with the start winding and opens its normally closed contacts when cemf reaches pickup voltage at about three-fourths of rated speed.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 338 ("Current Relays") (20th ed.: Section 16.3.5 (Motor Starting Relays — Current Relays))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, though its 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 CompressorRange adjustmentvsDifferential (combination) adjustment
A range adjustment moves cut-in and cut-out equally in the same direction (differential unchanged), while a combination differential adjustment changes cut-in and cut-out by equal amounts in opposite directions to keep the same average temperature while lengthening run time and cycle interval.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 325 ("Range Adjustment") (20th ed.: Section 16.2.1 (Range Adjustment))Inductive reactancevsCapacitive reactance
Inductive reactance opposes a change in current and causes current to lag behind voltage, while capacitive reactance causes voltage to lag behind current (resistance keeps them in phase).
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 14 - Electrical Power, Page 274 ("Inductive Reactance") (20th ed.: Section 13.1.2 (Power Loss — Inductive Reactance))Capacitors wired in seriesvsCapacitors wired in parallel
Series connection raises the total voltage level the capacitor assembly can handle (VCT = VC1 + VC2 + …), while parallel connection increases total capacitance.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 19 - Servicing Electric Motors and Controls, Page 381 (Section 19.1.1) (20th ed.: Section 17.2.1 (Motor Capacitors, Pro Tip: Capacitor Wiring))Hermetic compressor THR factorvsOpen-drive compressor THR factor
Total heat of rejection is compressor capacity × 1.30 for hermetic compressors versus × 1.25 for open-drive, because the hermetic motor adds heat inside the refrigerant stream.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 52 - Commercial Refrigeration Component Selection, Page 1282 (Section 52.1.2) (20th ed.: Chapter 51, Section 51.1.2 — Selecting a Condenser)Recycled refrigerantvsReclaimed refrigerant
EPA regulations prohibit a change of ownership of recycled refrigerant; refrigerant must be reclaimed to AHRI Standard 700 purity, verified by chemical analysis, before it can be sold or used in another owner's system.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 11 - Equipment and Instruments for Refrigerant Handling and Service, Page 212 (Section 11.7) (20th ed.: Pages 225-228)Dual-voltage three-phase motor wired for high voltage (480 V)vsDual-voltage three-phase motor wired for low voltage (240 V)
The three sets of stator windings are connected in series for the higher voltage and in parallel for the lower voltage; operating on the higher voltage draws less current and is more efficient.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 16 - Electric Motors, Page 309 (Section 16.2.3) (20th ed.: Section 15.2.2 (Three-Phase Motors))Liquid line restriction (TXV system)vsInefficient compressor
A liquid line restriction gives low suction pressure, low head pressure, high superheat, and normal subcooling, while an inefficient compressor shows HIGH suction pressure with LOW head pressure.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 48 - Troubleshooting Commercial Systems—System Diagnosis, Page 1202 (20th ed.: Ch. 53, Fig. 53-20 / High-Side Restriction)Key Terms
Zeotropic refrigerant blend (400 series, e.g., R-410A) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 12 - Working with Refrigerants, Page 243 (20th ed.: Page 259)
A blend whose component refrigerants vaporize at different temperatures, so it must always be charged into a system as a liquid.
Fractionation Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 12 - Working with Refrigerants, Page 243 (20th ed.: Page 259)
The splitting of a zeotropic blend into its component refrigerants—caused by vapor charging, with the lowest boiling point component entering the system first and creating an improper mixture.
Recovery cylinder Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 11 - Equipment and Instruments for Refrigerant Handling and Service, Page 189 (Section 11.1.3) (20th ed.: Page 200)
A refrigerant cylinder identified by gray paint on the lower portion and yellow paint on the upper portion, distinguishing it from disposable cylinders.
Reclaimed refrigerant Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 11 - Equipment and Instruments for Refrigerant Handling and Service, Page 212 (Section 11.7) (20th ed.: Pages 225-228)
Recovered refrigerant processed to meet AHRI Standard 700 purity specifications, verified by chemical analysis, which is required before refrigerant can change ownership.
HCFC (hydrochlorofluorocarbon) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 12 - Working with Refrigerants, Page 249 (20th ed.: Page 265)
The refrigerant class that includes R-22, which is being phased out in the United States due to its negative environmental impact and is commonly retrofitted with HFCs such as R-404A, R-407C, and R-410A.
Crankcase pressure regulator (CPR) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter Glossary - Glossary, Page 1330 (20th ed.: Chapter 19, Section 19.2.3)
A valve with an adjustable pressure setting that throttles suction pressure above its setting to keep crankcase pressure from exceeding a preset safe value, important after defrost cycles or long off cycles.
Evaporator pressure regulator (EPR) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 47 - Installing Commercial Systems, Page 1148 (20th ed.: Page 1404 (Section 52.4.1))
A valve at a warmer evaporator's outlet in a multiple-evaporator system that closes when suction line pressure drops below its set point, maintaining higher pressure and thus a higher saturation temperature in that evaporator.
Thermal overload Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 9 - Basic Refrigeration and Air-Conditioning System Components, Page 142 ("Compressor Overload Devices") (20th ed.: Chapter 19, Section 19.2.2)
A compressor protection device mounted on the compressor shell near the motor terminals that opens the power circuit to shut off the compressor when it overheats from causes such as lack of oil, shorted windings, or high head pressure from a blocked or dirty condenser.
Discharge line pressure switch Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 43 - Commercial Compressors, Page 1037 (Section 43.2.8) (20th ed.: Chapter 19, Section 19.2.4 — Discharge Line Pressure Switches)
A pressure-responsive, normally closed switch that opens the compressor control circuit to shut the compressor off when head pressure gets too high.
Intercooler Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 46 - Commercial Refrigeration System Configurations, Page 1134 (Section 46.4.1) (20th ed.: Chapter 49, Section 49.4.1 — Compound Refrigeration Systems)
A heat exchanger between the low-stage and high-stage compressors of a compound system that removes superheat from the low-stage discharge vapor (cooling but not condensing it) before it enters the high-stage compressor.
Impedance Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 354 (Section 17.6.1) (20th ed.: Section 16.5.2 (DDC System Components — Controlled Devices, Lockout Relay))
The opposition to the flow of alternating current in an ac circuit; a lockout relay uses a high-impedance coil to prevent enough current from reaching the compressor relay coil to energize it after a safety control opens.
Ladder diagram Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 368 (Section 18.2.1) (20th ed.: Section 16.1.2 (Ladder Diagrams))
A diagram with two parallel vertical power lines in which each horizontal rung represents an individual circuit containing a load plus any switches, relays, or control devices for that load.
Permanent split capacitor (PSC) motor Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 16 - Electric Motors, Page 306 ("Permanent Split Capacitor Motors") (20th ed.: Section 15.2.1 (Permanent Split Capacitor Motors))
A single-phase motor that keeps one run capacitor in series with the start winding for its entire operation and uses no centrifugal switch or relay.
Positive temperature coefficient (PTC) relay Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 346 (Section 17.5) (20th ed.: Section 16.3.5 (Motor Starting Relays — Positive Temperature Coefficient Relays))
A thermistor-based starting relay that develops very high resistance when heated and requires a cool-down period of typically two to five minutes before the motor can restart.
High-pressure motor control Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 334 ("High-Pressure Motor Controls") (20th ed.: Section 16.3.4 (Pressure Motor Controls — High-Pressure Motor Controls))
A safety control that cuts out the compressor, usually at 20% above normal head pressure, to prevent oil and refrigerant breakdown, carbon formation, and other damage.
Permissible noise exposure (8-hour) 29 CFR 1926, Subpart D, §1926.52(a)
Per 29 CFR 1926.52(a) and Table D-2, 90 dBA slow response is the maximum for an 8-hour duration, above which feasible engineering or administrative controls—and then PPE—are required.
Formulas to Know
Transformer secondary voltage / turns
VS/VP = NS/NP — e.g., VS/120 = 50/100 → VS = 60 V; and 24/120 = NS/100 → NS = (24 × 100)/120 = 20 turnsElectrical power (Watt's law)
P = I × E — e.g., 15 A × 240 V = 3,600 WPower factor
PF = (True power ÷ Apparent power) × 100 — e.g., (1000 W ÷ 1200 VA) × 100 ≈ 83%Motor synchronous speed
NS = 120 × (f ÷ P) — e.g., 120 × (60 ÷ 4) = 1800 RPM (about 1750 RPM operating, due to slip)Minimum acceptable motor operating voltage
Equipment operates within ±10% of rated voltage; minimum = rated × 0.90 — e.g., 240 V × 0.90 = 216 V (below 90% risks overheating)Required compressor capacity
Capacity (Btu/hr) = total heat load (Btu/day) ÷ operating cycle (hr/day); warm air defrost uses a 16-hour cycle — e.g., 192,000 ÷ 16 = 12,000 Btu/hr; 96,000 ÷ 16 = 6,000 Btu/hrTotal heat of rejection (condenser sizing)
THR = compressor capacity × 1.30 (hermetic) or × 1.25 (open-drive) — e.g., 30,000 Btu/hr × 1.30 = 39,000 Btu/hrCondensing temperature (air-cooled)
Condensing temp = ambient design temperature + TD (TD generally 10°F–30°F) — e.g., 95°F + 25°F = 120°FLiquid receiver sizing
Receiver = total system liquid volume × 1.15 (15% larger) — e.g., 20 gal × 1.15 = 23 gal minimumMaximum refrigerant weight in a recovery cylinder (AHRI Guideline K)
W = 0.8 × WC × SG (80% × water capacity × specific gravity of the refrigerant)