Exam Cheat Sheet · Quick Reference

Oklahoma Refrigeration Contractor

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

Passing score

70%

Exam time

210 min

Administered by

PSI Services Contractor

Format

Reference materials allowed

Oklahoma State Portion 80 questions

Electrical Knowledge and Controls 20 Q · 25%

Basic electrical principles: voltage, current, resistance, and Ohm's LawSeries, parallel, and series-parallel circuit analysisElectrical power calculations: Watt's Law, power factor, and apparent vs. true powerSingle-phase and three-phase power supply systemsMotor types and starting methods: split-phase, CSIR, CSCR, PSC, and shaded-pole motorsMotor starting and running relays: current, potential, solid-state, and PTC relaysTemperature and pressure motor controls: cut-in, cut-out, range, and differential adjustmentElectrical test equipment use and motor troubleshooting proceduresControl transformers and 24-volt control circuits

Refrigerants 20 Q · 25%

Refrigerant classification and numbering systems (CFC, HCFC, HFC, HFO, HC, inorganic)Environmental impact of refrigerants (ODP, GWP, Montreal Protocol, Clean Air Act Section 608)Refrigerant cylinder types, color codes, and DOT regulationsRefrigerant recovery, recycling, and reclaiming procedures and equipmentLeak detection methods and refrigerant leak repair requirementsSystem evacuation methods (deep vacuum and triple evacuation)Refrigerant charging procedures (by weight, vapor vs. liquid charging)Refrigeration lubricant types and compatibility with refrigerants

Piping 5 Q · 6%

ACR copper tubing types, sizing, and specifications (soft vs. hard-drawn, Type K and L)Tubing cutting and bending techniques (tubing cutters, hacksaws, bending springs, lever benders)Flared connections (single and double flares, flare fittings, flaring procedures)Soldering and brazing procedures (filler metals, flux, flame types, purging with nitrogen)Swaged connections and specialized tube couplings for dissimilar metalsNon-refrigerant piping materials (plastic pipe types ABS/PVC/CPVC, steel pipe, copper water tubing)IMC refrigerant piping material standards, fitting standards, and joint types by material (Section 1107-1108)Refrigerant piping installation requirements and pressure testing (location restrictions, stop valves, field pressure and leak testing per IMC Section 1109-1110)

Refrigeration Equipment and Components 20 Q · 25%

Compressor types and drive configurations (reciprocating, rotary, scroll, screw, centrifugal; open-drive, hermetic, semi-hermetic)Metering device types and operation (capillary tubes, metering orifices, TXVs, AXVs, EEVs, float controls)Evaporator types and construction (fin-and-tube, plate, microchannel; air-cooling vs. liquid-cooling; defrost methods and controls)Condenser types and construction (air-cooled, water-cooled, evaporative; head pressure control methods)Refrigerant flow and control components (filter-driers, liquid receivers, sight glasses, solenoid valves, check valves, service valves, pressure-regulating valves)Compressor safety and protection devices (overloads, crankcase pressure regulators, discharge pressure switches, accumulators, oil separators)Commercial refrigeration system configurations (multiple-evaporator systems, modulating/parallel compressor systems, compound and cascade systems, secondary loop systems)Commercial refrigeration applications and equipment selection (display cases, walk-in cabinets, component sizing, heat load fundamentals)

Refrigeration Systems Operations 10 Q · 12%

Refrigeration cycle fundamentals (compression, condensing, metering, evaporation phases)Pressure-enthalpy diagram analysis for diagnosing system conditionsEffects of refrigerant charge (undercharge and overcharge) on system performanceNoncondensables and moisture contamination in refrigeration systemsHeat load calculation and component sizing for commercial systemsCommercial system configurations (multiple-evaporator, modulating, multistage, secondary loop)Troubleshooting and diagnosis of common system symptoms (pressures, temperatures, superheat, subcooling)Installation, servicing, and component selection for commercial refrigeration systems

Safety 5 Q · 6%

Personal protective equipment (PPE) selection and useLockout/tagout (LOTO) procedures for electrical and mechanical systemsFire protection and portable fire extinguisher requirementsRefrigerant and compressed gas cylinder handling and storageHazard communication and safety data sheets (SDS)Flammable and combustible liquid storage and handlingFirst aid, medical services, and emergency action plansWelding and cutting safety including gas cylinder and torch procedures

Key Distinctions

ACR Tubing SizingvsCopper Water Tubing Sizing

ACR tubing is sized by its actual outside diameter, while copper water tubing nominal size equals the outside diameter minus 1/8 inch.

Modern Refrigeration And Air Conditioning, Chapter 8, Section 8.1.1

Galvanized PipevsBlack Pipe

Galvanized pipe is coated with zinc for corrosion resistance and used primarily in water systems, while black pipe is less expensive and used for gas lines and non-water applications.

Modern Refrigeration And Air Conditioning, Chapter 8, Section 8.2.3

Hot-Gas Defrost ValvevsHot-Gas Bypass Valve

The defrost valve delivers large quantities of hot gas to rapidly melt evaporator frost, while the bypass valve meters small amounts of hot gas to prevent compressor damage under low-load conditions.

Modern Refrigeration and Air Conditioning, 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 opens on decreasing current, while a potential relay coil is wired in parallel with the start winding and opens on rising counter-EMF voltage.

Modern Refrigeration and Air Conditioning, Section 16.3.5 (Motor Starting Relays — Current Relays)

Motor StartervsContactor

A motor starter includes built-in overload protection to prevent motor burnout, while a standard contactor does not.

Modern Refrigeration and Air Conditioning, Section 16.3.5 (Motor Starting Relays — Contactors and Motor Starters)

Single Screw CompressorvsTwin Screw Compressor

A single screw compressor uses one main rotor meshing with two star-shaped rotors, while a twin screw compressor uses two intermeshing helical rotors.

Modern Refrigeration and Air Conditioning, Chapter 18, Section 18.2.4 — Single Screw Compressor

Screw CompressorvsReciprocating Compressor

A screw compressor produces continuous, steady pressure with very little vibration due to its continuous pumping action, while a reciprocating compressor produces pulsating pressure.

Modern Refrigeration and Air Conditioning, Chapter 18, Section 18.2.4 — Screw Compressor Continuous Pressure

Temperature-Terminated DefrostvsTime-Based Defrost

Temperature-terminated defrost ends the cycle when a coil-mounted sensor detects sufficient warming, while time-based defrost runs for a fixed duration regardless of actual coil condition.

Modern Refrigeration and Air Conditioning, Chapter 21, Section 21.1.9

Permanent Split Capacitor (PSC) MotorvsCapacitor-Start, Capacitor-Run (CSCR) Motor

A PSC motor uses only a single run capacitor in the circuit at all times with no switching relay, while a CSCR motor uses both a start capacitor (dropped out at speed) and a run capacitor that stays in circuit.

Modern Refrigeration and Air Conditioning, Section 15.2.1 (Permanent Split Capacitor Motors)

Inductive ReactancevsCapacitive Reactance

Inductive reactance causes current to lag behind voltage, while capacitive reactance causes voltage to lag behind current.

Modern Refrigeration and Air Conditioning, Section 13.1.2 (Power Loss — Inductive Reactance)

Single-Phase PowervsThree-Phase Power

Single-phase power has moments where voltage reaches zero, while three-phase power provides constant power because the three voltage signals never all reach zero simultaneously.

Modern Refrigeration and Air Conditioning, Section 13.2.1 (Single-Phase and Three-Phase Power)

Electronic/Halide Leak DetectorvsBubble Solution Leak Detection

Electronic and halide detectors produce false positives near urethane foam insulation due to refrigerant chemicals used as expanders, while bubble solution relies on visible bubble formation and is unaffected by urethane foam.

Modern Refrigeration and Air Conditioning, Pages 221–223 (Sections 10.5.1, 10.5.3 Pro Tip, 10.5.4 Pro Tip)

Key Terms

Maximum Fire Extinguisher Travel Distance 29 CFR 1926, §1926.150(c)(1)(i)

Per 29 CFR 1926.150(c)(1)(i), the travel distance from any point of a protected building area to the nearest fire extinguisher on a construction site shall not exceed 100 feet.

Hazardous Waste Container Requirement 29 CFR 1926, Subpart C, §1926.25(c)

Per 29 CFR 1926.25(c), containers used for garbage and other oily, flammable, or hazardous wastes on a construction site must be equipped with covers.

Permissible Noise Exposure (8-hour) 29 CFR 1926, Subpart D, §1926.52(a)

Per 29 CFR 1926.52(a), the maximum permissible noise exposure level for an 8-hour workday on a construction site is 90 dBA slow response.

Employer PPE Cost Responsibility 29 CFR 1926, Subpart E, §1926.95(d)(1)

Per 29 CFR 1926.95(d)(1), all personal protective equipment required to comply with OSHA construction standards must be provided by the employer at no cost to employees.

First Aid Kit Inspection Frequency 29 CFR 1926, Subpart D, §1926.50(d)(2)

Per 29 CFR 1926.50(d)(2), first aid kit contents must be checked by the employer before each job and at least weekly on each job to ensure expended items are replaced.

First Aid Kit Container Requirement 29 CFR 1926, Subpart D, §1926.50(d)(2)

Per 29 CFR 1926.50(d)(2), first aid kit contents shall be placed in a weatherproof container with individual sealed packages for each type of item.

Construction Site Accident Prevention Inspections 29 CFR 1926, Subpart C, §1926.20(b)(2)

Per 29 CFR 1926.20(b)(2), employer accident prevention programs shall provide for frequent and regular inspections of job sites, materials, and equipment by competent persons designated by the employer.

Zeotropic Refrigerant Blend (Fractionation) Modern Refrigeration and Air Conditioning, Page 259

Zeotropic blends such as R-410A must be liquid charged because vapor charging causes individual refrigerants to fractionate, with the lowest boiling-point component filling the system first and creating an improper mixture.

Recovery Cylinder Color Code Modern Refrigeration and Air Conditioning, Page 200

Recovery cylinders are identified by gray paint on the lower portion and yellow paint on the upper portion, distinguishing them from disposable cylinders.

Power Factor Modern Refrigeration and Air Conditioning, Section 13.1.3 (Power Factor)

Power factor is the ratio of true power (watts) to apparent power (VA), expressed as a percentage; it indicates how effectively a circuit uses electrical power, and is improved in inductive circuits by adding capacitors.

PTC (Positive Temperature Coefficient) Relay Modern Refrigeration and Air Conditioning, Section 16.3.5 (Motor Starting Relays — Positive Temperature Coefficient Relays)

A PTC relay uses a thermistor that develops very high resistance when heated during motor operation and requires a cool-down period of typically two to five minutes before the motor can be restarted.

Synchronous Motor Speed Modern Refrigeration and Air Conditioning, Section 15.1.4 (Motor Speed — Synchronous Speed)

The synchronous speed of an AC induction motor is calculated as NS = 120 × (frequency / number of poles); for example, a 4-pole, 60 Hz motor has a synchronous speed of 1800 RPM.

High-Pressure Motor Control Set Point Modern Refrigeration and Air Conditioning, Section 16.3.4 (Pressure Motor Controls — High-Pressure Motor Controls)

A high-pressure motor control safety device is typically set to cut out the compressor at 20% above normal head pressure to prevent refrigerant and oil breakdown.

DDC Signal Range Modern Refrigeration and Air Conditioning, Section 16.5 (Direct Digital Controls)

In a Direct Digital Control (DDC) system, wiring between the controller and sensors carries low-voltage signals typically in the range of 0–10 Vdc or 4–20 mA.

Ultrasonic Leak Detector Modern Refrigeration and Air Conditioning, Page 223 (Section 10.5.5)

An ultrasonic leak detector detects the sound of vapor escaping from a pressurized system rather than the chemical composition of the refrigerant, making it compatible with all refrigerant types.

Liquid Line Restriction Symptoms (TXV System) Modern Refrigeration and Air Conditioning, Ch. 53, Fig. 53-20 / High-Side Restriction

A restriction in the liquid line of a TXV system causes low suction pressure, low head pressure, and high superheat while subcooling remains normal, because the evaporator is starved of refrigerant downstream of the functioning condenser.

Formulas to Know

Electrical Power (Watt's Law)P (watts) = I (amps) × E (volts)

Power FactorPower Factor (%) = (True Power in W / Apparent Power in VA) × 100

Transformer Voltage RatioVS / VP = NS / NP → VS = VP × (NS / NP)

Transformer Turns for Desired OutputNS = (VS × NP) / VP

Synchronous Motor SpeedNS (RPM) = 120 × f (Hz) / P (number of poles)

Minimum Acceptable Motor Voltage (±10% rule)Minimum voltage = Rated voltage × 0.90; Maximum voltage = Rated voltage × 1.10

Start free practice Full study guide