Oklahoma Refrigeration Journeyman

Key Concepts

Circuit Diagrams - Pictorial diagrams show components as they physically appear; used for wiring reference. - Ladder diagrams show the control circuit logically between two vertical "rails" (L1 and L2); used for troubleshooting logic and sequencing. Each rung represents one control function.

Ohm's Law, Watt's Law, and Power Factor - Voltage (V), Current (I), and Resistance (R) are the three fundamental electrical quantities. - Single-phase power factor = True Power (W) ÷ Apparent Power (VA). A power factor of 1.0 is unity (pure resistive load). Motors are inductive loads — power factor is always less than 1.0.

AC Motor Types - Single-phase: PSC (Permanent Split Capacitor), CSIR (Capacitor Start Inductor Run), CSCR (Capacitor Start Capacitor Run), shaded-pole. - Three-phase: No starting capacitors needed; self-starting due to rotating magnetic field. Used in larger commercial/industrial refrigeration. - PSC motors use a run capacitor only; CSIR uses a start capacitor only; CSCR uses both.

Motor Starting Relays - Current relay (amperage relay): Coil wired in series with the run winding; picks up on high starting current, drops out as motor accelerates. Mounted in one position only — coil orientation matters. - Potential relay: Coil wired across the start winding; normally closed contacts open when back-EMF rises as motor approaches full speed. Can be mounted in any position. - Solid-state relay: Uses a thermistor or electronic device to time out the start winding. No…

Key Concepts

Refrigerant Classification & Numbering (ASHRAE 34)

• CFCs (R-11, R-12, R-113): Chlorofluorocarbons — highest ODP, fully phased out under Montreal Protocol
• HCFCs (R-22, R-123, R-502): Hydrochlorofluorocarbons — lower ODP than CFCs, being phased out (R-22 production/import banned since 2020)
• HFCs (R-134a, R-404A, R-410A, R-507): Hydrofluorocarbons — zero ODP, high GWP, currently regulated under AIM Act
• HFOs (R-1234yf, R-1234ze): Hydrofluoroolefins — zero ODP, very low GWP, mildly flammable (A2L)
• HCs (R-290 propane, R-600a isobutane): Hydrocarbons — zero ODP, low GWP, highly flammable (A3)
• Inorganic series (R-700 series): R-717 (ammonia), R-718 (water), R-744 (CO₂) — numbered 700 + molecular weight

Safety Classification (ASHRAE 34)

• Letter = toxicity: A (lower toxicity), B (higher toxicity)
• Number = flammability: 1 (none), 2L (mildly flammable), 2 (flammable), 3 (highly flammable)
• R-22 = A1 | R-717 (ammonia) = B2L | R-410A = A1 | R-290 = A3 | R-1234yf = A2L

Environmental Impact

• ODP (Ozone Depletion Potential): Referenced against R-11 (ODP = 1.0). HFCs and HFOs = 0 ODP
• GWP (Global Warming Potential): Referenced against CO₂ (GWP = 1). R-404A ≈ 3,922; R-410A ≈ 2,088; R-744 = 1
• Montreal Protocol: International treaty phasing out ozone-depleting substances (CFCs first, then HCFCs)
• Clean Air Act Section 608: Prohibits venting of CFCs, HCFCs, and HFCs; requires certified technicians; mandates recovery equipment use

Key Concepts

ACR Copper Tubing Types & Specifications

• ACR tubing (Air Conditioning & Refrigeration) is cleaned, dehydrated, and capped at the factory — it is not the same as plumbing copper.
• Common types: Type L (most common for refrigeration) and Type K (heavier wall, underground/high-pressure). Type M is not approved for refrigerant service.
• ACR tubing is sized by OD (outside diameter), unlike plumbing copper which is sized by nominal ID.
• Available hard-drawn (straight lengths) and soft-drawn (coils); soft-drawn used for field bending.

Tubing Work Techniques

• Cutting: Use a tubing cutter — do not use a hacksaw (leaves burrs and filings that contaminate the system).
• Reaming: Always ream after cutting to remove the interior burr; burrs restrict flow and cause turbulence.
• Bending: Use a proper tube bender to avoid flattening or kinking. Soft (annealed) copper bends; hard-drawn requires fittings for direction changes.

Flared Connections

• Single flare: Standard for most refrigerant service; formed at 45°. Used with flare nuts and fittings.
• Double flare: Stronger, used where vibration is a concern (e.g., automotive/some commercial apps). Two-step process folding the flare back on itself.
• Tubing must be cut square, reamed, and deburred before flaring. Flare nut goes on before flaring.
• Over- or under-flaring causes leaks; flare should be smooth and uniform with no cracks.

Oklahoma Refrigeration Journeyman Exam — Study Brief

Key Concepts

Compressor Types and Drive Configurations

• Open-drive compressors use an external motor connected via direct-drive (shaft coupling, same RPM) or belt-drive (pulley ratio determines speed). Require a shaft seal to prevent refrigerant leaks — the most common failure point.
• Hermetic compressors: Motor and compressor sealed in one welded unit. Semi-hermetic (serviceable bolted housing) vs. fully hermetic (welded, not field-serviceable).
• Reciprocating: Piston/cylinder design; uses suction and discharge reed valves; most common in commercial refrigeration.
• Rotary: Rotating vane or stationary blade; compact, quiet; common in small applications.
• Scroll: Two inter-fitting spirals; one fixed, one orbiting; no suction/discharge valves; highly efficient, fewer moving parts.
• Screw: Male/female helical rotors; high capacity, continuous compression; used in large commercial/industrial systems.
• Centrifugal: Uses impeller and volute; compresses by centrifugal force; used in large-tonnage chiller applications; susceptible to surge at low load.

Metering Devices

• Capillary tube: Fixed restriction; no moving parts; used in small, factory-charged systems; critically matched to system.
• TXV (Thermostatic Expansion Valve): Maintains constant superheat at evaporator outlet; controlled by bulb temperature, evaporator pressure, and spring setting.
• AXV (Automatic/Constant Pressure Expansion Valve): Maintains constant evaporator pressure regardless of load — opposite control logic from TXV.
• EEV (Electronic Expansion Valve): Stepper motor controlled; most precise; used with electronic controls and variable loads.
• Float valves: High-side…

Oklahoma Refrigeration Journeyman Exam | 5 Questions, 8% of Exam

Key Concepts

Compression Refrigeration Cycle Components - Compressor (high-side): Raises refrigerant pressure and temperature; separates high-side from low-side - Condenser (high-side): Rejects heat; converts high-pressure vapor to liquid - Metering device/expansion valve (dividing point): Drops pressure; separates high-side from low-side - Evaporator (low-side): Absorbs heat; converts low-pressure liquid to vapor

High-Side vs. Low-Side Pressure - High-side: from compressor discharge → through condenser → to metering device inlet - Low-side: from metering device outlet → through evaporator → to compressor suction - High-side pressure corresponds to condensing temperature; low-side pressure corresponds to evaporating temperature

Heat Transfer Methods - Conduction: Heat transfer through direct contact (e.g., refrigerant absorbing heat through evaporator walls) - Convection: Heat transfer via fluid/air movement (e.g., forced-air evaporators) - Radiation: Heat transfer via electromagnetic waves without contact (e.g., solar load on a refrigerated case)

Sensible Heat, Latent Heat, Superheat, and Subcooling - Sensible heat: Heat that causes a measurable temperature change; no phase change occurs - Latent heat: Heat absorbed/rejected during a phase change with no temperature change - Latent heat of fusion: solid ↔ liquid - Latent heat of vaporization: liquid ↔ vapor - Superheat: Temperature of a vapor above its saturation temperature at a given pressure (suction superheat = actual suction temp − saturation temp at suction pressure) - Subcooling: Temperature of a liquid below its…

5 questions | 8% of exam

Key Concepts

Personal Protective Equipment (PPE)

Per 29 CFR 1926.20(f)(1), employers must provide PPE to each individual employee — failure to provide PPE to even one employee is a separate violation. For refrigeration work, appropriate PPE includes safety glasses, chemical-splash goggles, gloves rated for refrigerants, and hearing protection where applicable.

Lockout/Tagout (LOTO)

Unsafe equipment must be rendered inoperable by tagging or locking controls before work begins (29 CFR 1926.20(b)(3)). Only qualified persons (trained and experienced) may operate equipment (1926.20(b)(4)). LOTO sequence: shut down → isolate energy → lock/tag → release stored energy → verify zero energy state.

Fire Protection – PASS Method & Extinguisher Types

Per 29 CFR 1926.24, employers are responsible for an effective fire protection and prevention program. Know extinguisher classes: - Class A – Ordinary combustibles (wood, paper) - Class B – Flammable liquids and gases - Class C – Electrical equipment (use CO₂ or dry chemical — never water) - Class D – Combustible metals - Class K – Cooking oils/fats

PASS method for extinguisher use: 1. Pull the pin 2. Aim at the base of the fire 3. Squeeze the handle 4. Sweep side to side