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Refrigerant Recovery curriculum

9 chapters
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149 concepts
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free
Everything the adaptive question bank can teach and test in Refrigerant Recovery, from foundations through advanced practice. Work through it in order, or start practising and let the questions find your level.
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A free 17-minute primer — the mental model, the mistakes beginners make, and what to practise first.
A. Shared recovery mechanics
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Self-contained (active) vs system-dependent (passive) recovery equipment.
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80% fill by weight — hydrostatic rupture risk beyond.
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Mostly air; raises head pressure; check by comparing cylinder pressure to the PT chart at known temperature.
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Saturated pressure ⇄ temperature reading (computed family).
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Evacuation for moisture removal: microns, the 500-micron target, triple evacuation with nitrogen sweeps.
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A vacuum pump is not a recovery device.
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Change when opening a system; moisture + POE oil forms acid.
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Hose diameter/length, cylinder chilling, liquid-first strategy.
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R-12 → R-134a basics: mineral → ester/POE oil, fittings and label changes.
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Recovery removes refrigerant; evacuation removes air and moisture — two jobs, two machines, two success criteria.
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Starting, running and shutting down a self-contained recovery machine in the right order.
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Purging hoses and clearing the machine so residual refrigerant is neither lost nor carried into the next job.
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Low-loss fittings and self-sealing connections, and the de minimis standard they exist to satisfy.
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Clearing the recovery machine's internal volume before switching to a different refrigerant.
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Dedicating hoses, gauges and machines by refrigerant family to stop cross-contamination at the source.
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Push-pull liquid recovery on a large charge: the setup, the speed gain, and the point where it stalls.
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Vapour recovery versus liquid recovery, and the order-of-magnitude time difference between them.
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Matching the recovery cylinder's rated service pressure to the refrigerant being removed.
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Recovering onto a scale so the fill limit is a measured number rather than an estimate.
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Cold ambient slowing recovery; warming the appliance and chilling the cylinder to keep a pressure difference working.
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Pressure rising again after shutdown as the signal that recovery is not actually finished.
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Isolating the machine and letting the appliance stand to confirm the required level actually holds.
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Filters, oil and check valves on the recovery machine itself, and the performance loss when they are ignored.
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Oil drawn out with the refrigerant: measuring it, recording it, and disposing of it as a waste stream.
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Establishing the appliance's charge before starting, so "done" is a number rather than a feeling.
B. Type I — small appliances
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<5 lb charge, hermetically sealed: household fridge, window AC, dehumidifier, vending machine.
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Compressor operating → 90%; not operating → 80%; or 4 in Hg vacuum.
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Solderless piercing valves leak — remove or braze after service.
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Passive recovery rides the appliance's compressor or pressure differential.
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A hermetically sealed unit has no service valves, which is why access must be created before anything can be recovered.
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Piercing valve versus a brazed access fitting: speed against permanence, and what each leaves behind.
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Using the appliance's own compressor to move refrigerant, and what to do when it will not run.
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Setting up system-dependent recovery: cylinder chilled, appliance warmed, hoses routed to move vapour the right way.
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The vacuum alternative to the percentage levels, and how it is verified on a small appliance.
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The recovery percentages come from equipment certification, not from a field measurement the technician takes.
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Realistic recovery times on a small charge, and why a bigger machine does not fix a restricted access point.
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Repairing and resealing a hermetic system, and the leak test that has to follow.
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Recovering before disposal, and who may perform that recovery without certification.
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Reading the nameplate for refrigerant type and charge before connecting anything at all.
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Window units, dehumidifiers, vending machines and water coolers: configuration differences that change where access goes.
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Small appliances charged with flammable hydrocarbons, and what changes about recovery and ignition control.
C. Type II — high-pressure appliances
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Refrigerant boiling between −50°C and 10°C at atmospheric pressure (R-22, R-410A, R-404A).
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Required inches-of-vacuum by charge size, refrigerant class, and equipment date (computed-lookup family).
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Evacuate only to 0 psig when leaks make deeper vacuum pointless.
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Recover liquid, then vapor; nitrogen pressure-test then evacuate.
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Electronic detectors and soap bubbles; regulated nitrogen for pressurizing — never air via the compressor.
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Reading the required level off appliance class first, before any of the other columns matter.
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Why the required vacuum changes at the charge-size threshold, and how isolating a component moves you across it.
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Machines built before and after the standard's cutover are held to different achievable levels.
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Evacuating an isolated component instead of the whole appliance, and the receiver the charge must go to.
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Confirming the required level is actually reached before the system is broken into.
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The 0 psig ceiling for a non-major repair that will not be followed by an atmospheric release.
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Matching machine capacity to charge size so a large system does not consume a whole day.
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Hose diameter, length and every core in the path as the biggest controllable factor in recovery time.
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Chilling the recovery cylinder to maintain the pressure difference the machine is fighting.
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Warming the appliance to raise vapour pressure, and the limits on how that heat may be applied.
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Pumping down into the receiver to isolate a section for service, and where that stops being sufficient.
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Pressure-testing with regulated nitrogen after repair, and choosing the test pressure.
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Holding a vacuum and reading the rise: a leak, trapped moisture, and a tight system each look different.
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Reading the vacuum at the system rather than at the pump, and how large that difference really is.
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Weighing in the charge after evacuation and confirming it with operating readings.
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Recovering after a compressor burnout: filter placement, machine protection, and where that refrigerant must go.
D. Type III — low-pressure appliances
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Refrigerant boils above 10°C at atmospheric pressure (R-123/R-11 centrifugal chillers) — the machine runs in a vacuum.
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25 mm Hg absolute (≈29 in Hg vacuum).
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Controlled hot water or nitrogen to a MAX of 10 psig; the rupture disc protects.
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Why low-pressure systems continuously purge air; excessive purging signals a leak.
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Liquid first, then vapor with the recovery compressor; water in the tubes prevents freezing.
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Relief at 15 psig design limit.
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A low-pressure machine runs below atmospheric pressure, so its leaks draw air IN rather than pushing refrigerant out.
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Air in the machine raising condensing pressure and cutting capacity long before anything trips.
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High-efficiency purge units and how little refrigerant they should lose per unit of air removed.
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Logging purge run time as the leak indicator on a low-pressure chiller.
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Verifying the required absolute pressure with a gauge that can actually read it.
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Bringing the appliance to atmospheric pressure before opening it, and covering openings that cannot be isolated.
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Why nitrogen for pressurizing is restricted on low-pressure appliances, and the boiling-point test that decides it.
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Using heat rather than nitrogen to raise internal pressure, and the ceiling on how far it may be taken.
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What a ruptured disc means for the charge, the room and the return to service.
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Keeping water flowing or draining the tubes so evacuation does not freeze and split them.
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Monitoring for freeze-up during recovery, and the pauses that prevent it.
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The maximum leak-test pressure, and why exceeding it destroys the relief device.
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Controlled hot water as a leak-test method, and the tube-side hazards that come with it.
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Open-drive motors, shaft seals and oil systems as the service features unique to these machines.
E. The refrigeration cycle & components
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Compressor, condenser, metering device and evaporator, and what each does to pressure and temperature.
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Dividing the system at the compressor and the metering device — the map every service decision is drawn on.
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Where the refrigerant boils and where it condenses, and why recovery goes after the liquid first.
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Superheat as evidence about how the evaporator is being fed, and where it must be measured.
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Subcooling as evidence about charge level and condenser performance.
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Fixed orifice, thermostatic and electronic expansion valves, and how each reacts to a charge error.
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Reciprocating, scroll, screw and centrifugal, and what each implies for recovery strategy.
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Where liquid is stored in a system, and why recovery planning starts by finding it.
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Front-seat, back-seat and mid-seat positions, and isolating a component using them.
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Schrader cores and depressors, and the flow restriction a core adds to every recovery.
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Liquid-line and suction-line driers, and why flow direction is marked on the shell.
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Latent versus sensible heat, and why a refrigerant is chosen for the temperature at which it boils.
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Saturation as the bridge between a gauge pressure and an actual temperature inside the system.
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Overcharge, undercharge and restriction each produce a distinct pair of pressure readings.
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Heat-pump reversing valves, and how they move which side is the high side.
F. Gauges, instruments & measurement
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What the high and low gauges read, and what the centre hose is doing at any moment.
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Reading pressure and vacuum on the same dial without misreading which scale you are on.
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Where a digital manifold genuinely helps, and the readings it can still get wrong.
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Why a manifold gauge cannot measure a deep vacuum at all and a micron gauge can.
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Microns, inches of mercury and millimetres of mercury as three ways to state the same pressure.
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Converting a gauge reading into a saturation temperature with a pressure-temperature chart.
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Reading a blend's chart with separate bubble and dew columns, and picking the right one.
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Where a probe is attached and insulated, and how much a careless placement shifts the reading.
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Using an identifier to detect a mixed or contaminated charge BEFORE it enters your recovery cylinder.
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Resolution, calibration and levelling on a charging or recovery scale.
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Electronic, ultrasonic, fluorescent dye and bubble methods, and what each can and cannot find.
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Sensitivity settings, false positives, and confirming any hit with a second method.
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Pump displacement, oil condition, and the gap between a pump's rated and achievable vacuum.
G. Oils, moisture & contamination
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Mineral, alkylbenzene and polyol ester oils, and the refrigerant family each is matched to.
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Polyol ester oil pulling moisture out of the air within minutes of a container being opened.
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Moisture plus oil plus heat producing acid, and what that acid does to windings and metal.
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Testing oil for acid, and what a positive result obliges before the system goes back together.
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Cleaning up after a compressor burnout, and why a suction-line drier goes in temporarily.
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Open lines, wet nitrogen, an inadequate vacuum, and a leaking low-pressure machine.
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Ice at the metering device, sight-glass indicator colour, and intermittent operation.
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Comparing cylinder pressure to the chart at a known temperature to prove air is present.
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Purging air from a recovery cylinder correctly, and the venting rule that limits how it is done.
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Debris, filings and desiccant powder as system killers, and where filtration belongs.
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A mixed cylinder cannot be reclaimed to specification, so the whole quantity becomes a destruction cost.
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Recovered oil as a regulated waste stream with its own handling and disposal path.
H. Evacuation, charging & service practice
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Isolating the pump and reading the micron rise: the shape of the curve names the problem.
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Breaking the vacuum with dry nitrogen to carry moisture out, and how many cycles it is worth.
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Vacuum pump oil contaminating during the job, and changing it mid-procedure rather than afterwards.
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Evacuating through large-bore connections on both sides instead of through a single Schrader core.
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Charging by weight from the nameplate as the primary method, not a fallback.
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Trimming a charge by superheat or subcooling depending on the metering device fitted.
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Charging a blend as liquid while metering it so the compressor is never slugged.
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Why ambient temperature and load change what a correct charge looks like on the gauges.
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Working from most-likely to least-likely locations rather than sweeping the system at random.
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Test pressures by appliance class, and never using the system's own compressor as the pressure source.
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Holding a nitrogen pressure and correcting the reading for temperature change before calling it a leak.
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Repairing, then proving the repair, before any refrigerant goes back in.
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Recover, change oil, replace elastomers and drier, evacuate, recharge, label — in that order.
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Labelling the appliance with the refrigerant and oil actually in it, for whoever comes next.
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Recording quantities recovered and added, dates, and appliance identification.
I. Cylinders, transport & disposal
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Refillable recovery cylinders versus disposable ones, and why a disposable must never be refilled.
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Matching the cylinder's rated service pressure to the refrigerant it will hold.
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Hydrostatic retest dates on a refillable cylinder, and what an expired date means for using it.
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Using tare weight to compute net contents and turn the fill limit into an actual measurement.
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Why the fill limit is a function of temperature and not just a single percentage.
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Evacuating a new or previously used recovery cylinder before filling it.
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Valve caps, protective collars and hose connections between jobs.
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Upright, secured and ventilated transport, and the temperature a closed vehicle actually reaches.
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Marking, labelling and documentation that must travel with a shipped cylinder.
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Preparing and shipping recovered refrigerant for reclamation, and the records that go with it.
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The residual heel in an "empty" cylinder, recovering it, and disposing of the cylinder itself.
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On-site storage temperature, ventilation and segregation of filled cylinders.
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