Exam Cheat Sheet · Quick Reference
Oklahoma HVACR Journeyman Limited
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
180 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 and Watt's law calculationsSingle-phase and three-phase AC motors: types, starting methods, and capacitorsMotor starting relays: current, potential, solid-state, and PTC relaysPressure and temperature motor controls: cut-in, cut-out, range, and differential adjustmentMotor protection devices: fuses, circuit breakers, and bimetal/thermistor overload protectionElectrical test equipment: voltmeters, ammeters, ohmmeters, and multimetersTroubleshooting hermetic compressor motors: winding resistance, shorts, and groundsControl transformers and 24-volt control circuits
Natural Gas
9 Q · 15%
Gas piping materials, fittings, and allowable pipe types (steel, copper, CSST, PE)Gas piping sizing methods and capacity tables (longest length, branch length, hybrid pressure)Gas piping pressure requirements, testing, and leak checksCombustion air requirements for gas-fired appliances (indoor, outdoor, and combination methods)Venting system types and selection by appliance category (Type B, single-wall, direct-vent, Categories I-IV)Chimney and vent sizing for Category I appliances (draft hood and fan-assisted)Vent connector installation requirements, clearances, and termination locationsGas furnace combustion principles, ignition systems, and safety controls
Air Distribution Systems
10 Q · 17%
Duct types, construction materials, and system configurations (radial, extended plenum, reducing trunk, perimeter loop, SDHV)Duct sizing procedures and ACCA Manual D requirementsRegisters, diffusers, and grilles — selection, placement, and airflow characteristicsDampers — types (butterfly, multiple-blade, split, fire, smoke), installation, and automatic controlsDuct insulation, sealing methods, and vapor retarder requirements (IMC Chapter 6)Airflow measurement tools and techniques (flow hoods, manometers, pitot tubes, blower door testing, duct blaster testing)Ventilation requirements — air changes per hour, fresh air intake, positive/negative pressure, and IMC Chapter 4 outdoor airflow ratesDuct system service — balancing, noise troubleshooting, cleaning procedures, and air filter maintenance
Refrigeration and Air Conditioning Systems
13 Q · 22%
Compression refrigeration cycle components and operationRefrigerant classification, properties, and environmental regulations (EPA/Clean Air Act)Refrigerant handling equipment: cylinders, gauge manifolds, service valves, and leak detectionRefrigerant recovery, recycling, reclaiming, evacuation, and charging proceduresMetering devices: capillary tubes, TXVs, AXVs, EEVs, and fixed-orifice typesCompressor types, configurations, and safety protection componentsHeat exchangers: evaporator and condenser types, defrost methods, and head pressure controlRefrigerant flow components: filter-driers, sight glasses, check valves, solenoid valves, and pressure-regulating valves
Heating Systems
10 Q · 17%
Gas-fired heating systems: burners, ignition systems, and combustion controlsOil-fired heating systems: burner components, fuel delivery, and combustion efficiency testingHydronic heating system components: boilers, circulating pumps, expansion tanks, and terminal unitsHeat pump operation: reversing valves, metering devices, and heating/cooling modesElectric resistance heating systems: furnaces, duct heaters, baseboard units, and radiant heatHydronic system designs: series loop, one-pipe, two-pipe, zoned, and radiant systemsBoiler safety controls and code requirements: pressure relief valves, low-water cutoffs, and IMC Chapter 10 provisionsForced-air furnace types and efficiency ratings: upflow, downflow, condensing vs. noncondensing, and AFUE
Safety
3 Q · 5%
Electrical hazards and lockout/tagout (LOTO) proceduresFire hazards and fire extinguisher use (P.A.S.S.)Refrigerant cylinder safety and pressure hazardsPersonal protective equipment (PPE) selection and useHazard Communication Standard (HCS), GHS labeling, and safety data sheets (SDS)Breathing hazards and respiratory protectionLadder, scaffolding, and fall protection safetyConfined space safety and safe work practices
Key Distinctions
Pictorial wiring diagramvsLadder wiring diagram
A pictorial diagram shows all connections plus the approximate physical location of devices in the unit (and often wire colors), while a ladder diagram shows the order of component operation as horizontal rungs between two vertical power lines, with devices near the top energized first.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 369 (Section 18.2.2) (20th ed.: Chapter 16, Section 16.1.1)Current relayvsPotential relay
A current relay switches on run-winding current magnitude (terminals L = line, M = main/run winding, S = start winding; its contacts open as the motor accelerates and run-winding current drops), while a potential relay actuates on the counter electromotive force (cemf) built up in the start winding at about three-fourths of rated speed.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 339 (Section 17.4.5) (20th ed.: Chapter 16, Section 16.3.5 — Current Relays)Solid-state relay (SSR)vsElectromagnetic relay
An SSR switches circuits electronically with transistors, SCRs, or triacs with no physical movement of mechanical parts, whereas an electromagnetic relay uses mechanical contacts.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 345 ("Solid-State Relays") (20th ed.: Chapter 16, Section 16.3.5 — Solid-State Relays)Range adjustment (low-pressure motor control)vsDifferential adjustment (low-pressure motor control)
Turning the range screw clockwise raises both cut-in and cut-out an equal amount (differential unchanged), while the differential screw turned clockwise raises only the cut-out pressure and leaves cut-in unaffected.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 333 (Section 17.4.4) (20th ed.: Chapter 16, Section 16.3.4 — Low-Pressure Motor Controls)Subcooling charging methodvsSuperheat charging method
Subcooling is generally used to check charge on systems with thermostatic expansion valves (low subcooling = possible undercharge, high = possible overcharge), while superheat is used on fixed-orifice systems such as capillary tubes.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 12 - Working with Refrigerants, Page 221 (20th ed.: Page 236)Building-related illness (BRI)vsSick building syndrome (SBS)
BRI is a specifically diagnosable illness caused by exposure to airborne agents whose symptoms do not disappear when the occupant leaves, while SBS has no specific cause or identifiable illness and its symptoms disappear when occupants leave the building.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 29 - Air Quality, Page 647 (20th ed.: Page 730)K-value (thermal conductivity)vsC-value (thermal conductance)
K-value is heat passing through one square foot of material one inch thick in one hour per 1°F difference (Btu·in/hr·ft²·°F), while C-value is based on the material's actual measured thickness rather than a standardized 1-inch thickness.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 32 - Heating and Cooling Loads, Page 717 (20th ed.: Page 986)In-line ammetervsClamp-on ammeter
An in-line ammeter must be wired in series with the load (on dc, black lead to negative and red to positive), while a clamp-on ammeter encircles a single conductor — clamping both hot and neutral makes the opposing magnetic fields cancel and the meter reads zero.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 362 ("In-Line Ammeters") (20th ed.: Chapter 17, Section 17.1.3 — In-Line Ammeters)Duct leakage test before the air handler is installedvsDuct leakage test with the air handler installed
Per the IECC, maximum leakage is 3 cfm per 100 ft² of conditioned space when tested before the air handler is installed, versus 4 cfm per 100 ft² when tested with the air handler installed.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 31 - Ventilation System Service, Page 703 (Section 31.1.5) (20th ed.: Page 793)Radial duct systemvsPerimeter loop duct system
A radial system runs individual branch ducts directly from a central plenum to each outlet with no trunk line, while a perimeter loop system is used with downflow furnaces in slab homes without basements, with branches feeding a perimeter duct embedded in the slab.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 30 - Air Distribution, Page 672 (20th ed.: Page 755)Hot-surface igniter (glow coil)vsFlame rod
In an HSI system the glow coil is used only for ignition and cannot sense flame; a separate flame rod proves the flame by rectification, so a dirty or oxidized rod lets the burner light and then shuts off seconds later (HSI systems do not use thermocouples).
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 33 - Gas-Fired Heating Systems, Page 765 (20th ed.: Pages 1126-1128 (Sections 41.5.4 and 41.6.1))Current-limiting fusevsMultipurpose fuse
A current-limiting fuse uses temperature-sensitive resistors that open when current exceeds the limit and reclose when cooled (keeping motor current below rated locked rotor amperage), while a multipurpose fuse combines fast-acting and time-delay traits — it rides through small short-duration overloads such as motor starting but blows immediately above 500% of maximum rating.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 347 (Section 17.5.1) (20th ed.: Chapter 16, Section 16.4.1)Three-phase motor startingvsSingle-phase motor starting
A three-phase supply is already phase-split (the three currents peak at different times), so no start windings or capacitors are needed, and power is constant because voltages are never all zero at once; single-phase motors must create phase splitting.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 16 - Electric Motors, Page 308 (Section 16.2.2) (20th ed.: Chapter 15, Section 15.2.2)Key Terms
Ladder diagram Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 368 (Section 18.2.1) (20th ed.: Chapter 16, Section 16.1.2)
A wiring diagram in which the two vertical lines are the power supply and each horizontal rung is an individual circuit containing a load and the controls for it, arranged in order of component operation.
Pictorial diagram Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 369 (Section 18.2.2) (20th ed.: Chapter 16, Section 16.1.1)
A wiring diagram that shows all connections among a circuit's devices plus their approximate physical location in the unit, and may give wire colors.
PTC relay Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 346 (Section 17.5) (20th ed.: Chapter 16, Section 16.3.5 — Positive Temperature Coefficient Relays)
A positive temperature coefficient thermistor wired in parallel with the run capacitor that has low resistance (3 Ω to 12 Ω) when cool so start current takes that path, then rises to 10 kΩ–20 kΩ when heated, forcing current through the run capacitor.
Potential relay Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 339 ("Potential Relays") (20th ed.: Chapter 16, Section 16.3.5 — Potential Relays)
A motor starting relay that energizes on the counter electromotive force (cemf) induced in the start winding as the motor nears rated speed, opening its normally closed contacts at pickup voltage (about three-fourths of normal speed) to drop out the start capacitor.
Current relay terminals L, M, S Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 339 (Section 17.4.5) (20th ed.: Chapter 16, Section 16.3.5 — Current Relays)
L is line voltage, M is the main (run) winding, and S is the start winding; a normally open contact lies between L and S and the relay coil between L and M.
Differential (control) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 325 (Section 17.2.2) (20th ed.: Chapter 16, Section 16.2.2)
The difference between a control's cut-out and cut-in values, representing the swing during which the system cycles.
High-pressure motor control Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 334 ("High-Pressure Motor Controls") (20th ed.: Chapter 16, Section 16.3.4 — High-Pressure Motor Controls)
A safety control usually set to cut out at 20% above normal head pressure to protect the compressor from high pressure and temperature and the motor from overheating and overloading.
Internal bimetal overload protector Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 348 (Section 17.5.3) (20th ed.: Chapter 16, Section 16.4.3)
A protection device located inside the compressor on or in the motor windings whose bimetal disc bends open on excessive current or heat and recloses when cooled, causing the compressor to cycle off and restart.
Infinity (∞ / OL) ohmmeter reading Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 361 (Section 18.1.2) (20th ed.: Chapter 17, Section 17.1.2)
An open circuit in the conductor — a broken connection, blown fuse or breaker, or other open — whereas 0 Ω indicates good continuity.
Velocity pressure Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 28 - Air Movement and Measurement, Page 630 (20th ed.: Page 710)
The difference between total air pressure and static air pressure, measured by a pitot tube whose inner tube senses total pressure and outer side holes sense static pressure (total = static + velocity).
cfm50 Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 31 - Ventilation System Service, Page 702 (20th ed.: Page 791)
The measured airflow through a blower door fan when indoor pressure is held at −50 Pa with respect to outdoors, used to calculate ACH50.
Distributor (evaporator) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 45 - Commercial Metering Devices and Valves, Page 1088 (Section 45.1.4) (20th ed.: Pages 490-491)
A device at the metering device outlet that splits refrigerant into several shorter parallel evaporator paths, reducing pressure drop and giving more consistent coil temperature.
Crankcase heater Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 43 - Commercial Compressors, Page 1045 (Section 43.1) (20th ed.: Page 467)
An electric heating element on or in a compressor that keeps it warm during the Off cycle so refrigerant does not condense in the crankcase, preventing liquid slugging or a flooded start.
Sequencer (electric furnace) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 35 - Electric Heating Systems, Page 834 (20th ed.: Pages 1196 and 1205)
A device that closes and opens contacts on a time delay to energize heating elements one after another, typically about 30 seconds apart, to minimize initial current draw.
Overfiring Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 34 - Oil-Fired Heating Systems, Page 795 (Section 34.3.2) (20th ed.: Page 1154)
A condition in which a heating system creates too much heat, often from installing a higher-capacity burner nozzle than original, producing more heat than the heat exchanger can absorb and causing high stack temperature.
Category IV furnace Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 33 - Gas-Fired Heating Systems, Page 776 (20th ed.: Page 1134)
A positive-pressure venting, condensing furnace whose flue gas temperature is below 140°F (60°C) — under its dew point — so flue gas condenses; these high-efficiency units use secondary heat exchangers and PVC vent piping.
Refrigerant quality Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 51 - Understanding Heat Loads and System Thermodynamics, Page 1273 (20th ed.: Page 1372)
The fraction of refrigerant mass that is in the vapor state; 10% quality means 10% vapor and 90% liquid.
Panned joist space Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 30 - Air Distribution, Page 672 (20th ed.: Page 755)
A basement return-air branch duct formed by using the joists and floorboards as three sides of the duct.
Draft (oil furnace test) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 34 - Oil-Fired Heating Systems, Page 796 (20th ed.: Page 1155)
The movement of flue gas, measured with a draft gauge in inches of water column, indicating how quickly flue gases pass through the heat exchanger.
Small duct, high-velocity (SDHV) system Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 30 - Air Distribution, Page 666 (20th ed.: Page 748)
An air distribution system using small-diameter ducts at high velocity, with supply air delivered to the building's inside perimeter and return air taken from the center of the building.
Formulas to Know
Ohm's law (resistance and current)
R = E ÷ I and I = E ÷ R; e.g., 240 V ÷ 10 A = 24 Ω, and in a series circuit 24 V ÷ 8 Ω = 3 A flowing equally through every load.Watt's law (single-phase power)
P = I × E; e.g., 20 A × 120 V = 2400 W, 15 A × 240 V = 3600 W, 8 A × 240 V = 1920 W.Control differential and series voltage drops
Differential = higher value − lower value: for a heating system cut-out − cut-in (74°F − 68°F = 6°F), for a cooling system cut-in − cut-out; in a series circuit the sum of all individual voltage drops equals the total applied voltage (VD1 + VD2 + VD3 = 24 V).Air velocity from pitot-tube velocity pressure, and anemometer temperature correction
V = 4005 × √Pv (Pv in in. w.c.); e.g., 4005 × √0.25 = 2003 ft/min. Swinging-vane anemometer correction: velocity = instrument reading × √((460 + T) ÷ (460 + 68)).Air changes per hour and ACH50
ACH = (cfm × 60) ÷ room volume in ft³; ACH50 = (cfm50 × 60) ÷ conditioned volume; e.g., (1,500 × 60) ÷ 12,000 = 7.5.Motor synchronous speed and slip
NS = (120 × frequency) ÷ number of poles; 4-pole at 60 Hz = (120 × 60) ÷ 4 = 1800 RPM, and with 4%–5% slip actual full-load speed ≈ 1750 RPM.Coefficient of performance from a pressure-enthalpy diagram
COP = refrigeration effect ÷ heat of compression = (compressor inlet h − evaporator inlet h) ÷ (compressor outlet h − compressor inlet h); (179 − 116) ÷ (198 − 179) = 63 ÷ 19 = 3.32:1.Heat loss / heating load through building surfaces
Q = U × area × temperature difference, applied as HTM = U × HTD then load = area × HTM; e.g., wall HTM = 0.07 × 50 = 3.50, 136 ft² × 3.50 = 476 Btuh; glass HTM = 0.30 × 50 = 15.00, 60 ft² × 15.00 = 900 Btuh; net wall = (24 ft × 9 ft) − 60 ft² glass − 20 ft² door = 136 ft². Single glass constant method: 1.13 × 70°F TD × 12 ft² = 949 Btu/hr.Slab-on-grade and infiltration heat loss additions
Slab heat loss = building perimeter (linear feet) × 18 Btu/hr per foot (0°F outdoor design temp), added to above-ground losses; infiltration heating load counts sensible only: Qs = 0.018 × CFH × TD.Duct design friction rate, aspect ratio, and length/leakage/charge quick math
Friction rate = (ASP ÷ TEL) × 100 = (0.20 ÷ 250) × 100 = 0.08 in. WC per 100 ft; keep aspect ratio near 1:1 (20×5 duct has 50 in. perimeter vs 40 in. for 10×10 at equal 100 in² area = 25% more material); straight duct length = sum of labeled segments (28 + 22 + 15 = 65 ft, excluding elbow allowances); outdoor-air % = outdoor cfm ÷ total mixed cfm (1,000 ÷ 4,000 = 25%).