A refrigeration technician's training library and field reference.
Three areas — Diagnosis Fundamentals, Deep Technical Chapters, and Field Rules — with 42 chapters of field reasoning, cause and effect, measurements and evidence. Built to take you from basic understanding toward competent Cert II/Cert III thinking and experienced field diagnosis.
Troubleshoot from evidence, not habit
The foundation every technician should understand before moving into advanced fault finding. The six diagnostic categories, the diagnostic method, and the application and environmental factors that decide whether a system fault is actually a refrigeration fault.
The Diagnostic Method
The Diagnostic Method
A repeatable method: Complaint → Observation → Choose a logical starting point → Test → Prove → Follow the evidence → Identify root cause → Verify the repair.
The Six Diagnostic Categories
Supply, Control, Transmission, Components, User/Application, Environmental — diagnostic categories, not a rigid sequence.
Don't Be a Sucker for OEM Training
The fundamentals transfer between manufacturers. Learn the principles first, then use OEM documentation for what's different about that particular system — not as a crutch that stops you thinking.
Application & Environment
User / Application Factors
Refrigeration systems operate according to the application they were designed for. When the application changes, the system may no longer be adequate — and that is not a refrigeration fault.
Environmental Factors
Environmental conditions plus application load equal refrigeration demand. When the environment changes, the system's ability to cope changes.
The serious technician's reference library
Individual chapters for each technical subject that deserves its own treatment — pressure testing and leak diagnosis, evacuation and micron diagnosis, rotalock and pressure-path diagnosis, oil return and piping, charge and metering, components and systems, electrical, controls and commissioning. Cross-referenced, not duplicated.
Pressure Testing & Leak Diagnosis
Pressure Testing & Nitrogen Leak Diagnosis
One deep chapter combining pressure testing and nitrogen leak diagnosis — why we test, nitrogen properties, equipment integrity, test boundaries, stabilisation, temperature effects, ghost leaks, locating and proving the leak, repair and retest.
Nitrogen Temperature Effect
Nitrogen is inert, but its pressure changes with temperature. A lower gauge reading does not automatically prove the system has leaked.
Ghost Leaks
A suspected pressure loss that looks like a system leak but is actually caused by test equipment, access fittings, temperature, isolation, valve passing, or poor stabilisation.
Supermarket Rack Pressure-Testing & Ball Valves
On racks and distributed systems, isolation valves can separate sections — but a closed ball valve is an assumption, not proof of a pressure boundary.
Test Pressure — Time and Place for Different Pressures
Higher pressure is not automatically better. Choose the test pressure for the job — for the boundary, the components, and the purpose.
Leak Diagnosis — Find It, Prove It, Clean It
Field leak finding: oil trails, "Big Blue", cleaning the joint, proving the leak, and rechecking after repair.
Compressor & Pressure Path
Rotalock & Pressure-Path Diagnosis
Trace and prove the pressure path: what pressure is trapped when isolated, what controls actually see, what safeties actually see — and how wrong valve positions cause callbacks.
Compressor Diagnosis
Is the compressor actually the fault? Prove supply, control and load before condemning the compressor.
Compressor Valves
Valve failure changes pumping capacity and discharge temperature. Understand what the valves do and how their failure shows up.
Discharge Valve Leakage
A leaking discharge valve re-expands hot gas and kills capacity — a specific, diagnosable failure.
Floodback
Liquid refrigerant returning to the compressor. Not the same as poor oil return — understand the difference.
Oil Management & Piping
Oil Return, Risers & Traps
How compressor oil circulates and returns, suction risers, traps, double risers, oil logging, oil separators, and the balance between oil-carrying velocity and pressure drop.
Refrigeration Piping
Line sizing, risers, traps, insulation and pipework that doesn't leak or oil-log.
Charge & Metering
Superheat
Suction line temperature minus saturation temperature at suction pressure. Tells you whether the evaporator is fed correctly.
Subcooling
Condensing temperature minus liquid line temperature. Tells you about charge and liquid-line restriction.
Incorrect Subcooling & Its Effects
Subcooling set wrong — too high or too low — causes capacity loss, floodback, and callbacks.
Refrigerant Charging
Weighing in, charging by superheat or subcooling, and not guessing.
Shortage of Refrigerant
Low charge: low suction, high superheat, low subcooling, bubbles — and a leak that needs finding.
TXVs (Thermostatic Expansion Valves)
How a TXV controls feed, bulb placement, and what goes wrong with starving and flooding.
EEVs (Electronic Expansion Valves)
Step-motor or pulse valves controlled by a controller using sensors — more precise, but the diagnosis path is different.
Components & Systems
Blocked / Dirty Condensers
The most common cause of high head pressure — and the cheapest fix.
Refrigeration Components
Compressor, condenser, evaporator, metering device — what each does and what it should read.
Coldrooms
Sizing, install, defrost and the faults that keep them running — done properly.
Process Cooling
Refrigeration serving a process — tight tolerances, variable loads, and the process as part of the load.
Chilled Water Systems
Refrigeration cooling water, water cooling the load — diagnose the refrigeration side and the water side separately.
Glycol Systems
Antifreeze in the secondary loop — concentration, pump sizing, and the refrigeration-vs-secondary split.
Rack Systems
Multiplex racks — head pressure control, oil management, subcooling, and isolation for safe servicing.
LPG & Hatchery Systems
Specialist refrigeration applications with their own safety and operating requirements.
Electrical, Controls & Commissioning
Wiring Architecture — Before You Touch It
Walk up to unfamiliar equipment and mentally separate it into five circuit types — power, control, inputs, outputs, and communication. Don't memorise the machine. Understand the architecture.
Electrical Diagnosis
Follow the circuit to find the open, not just the dead component. Safe, methodical meter work.
Controls
LPs, HPs, oil safety, defrost and temperature control — what they protect, how they're set, and never from memory.
Fault Finding
The repeatable diagnostic method applied across the system — gather, read, theorise, test, prove, verify.
Commissioning
Set the system up so it runs right — evacuation, charge, settings, safeties, defrost, and recording the readings.
Pressure Drop
The balance between oil-carrying velocity, acceptable pressure drop, and system capacity.
What experienced techs know — the rules that prevent callbacks
Practical field knowledge: rules, warnings, common mistakes, verification routines and callback-prevention lessons. Not motivational — these are the rules that stop you cutting into a sound system or leaving a job unverified.
Core Field Rules
The Field Rules
The cross-cutting rules that apply across the whole trade — from evidence, equipment integrity, temperature, isolation, pressure paths, to oil-return balance.
Callback Prevention & Verification
The verification routines and common mistakes that separate a finished job from a callback.