C&G 2079-11 F-Gas Category I common mistakes
C&G 2079-11 F-Gas Category I · Understand the traps and how to avoid them.
Converting refrigerant charge into CO2-equivalent incorrectly - for example quoting a leak as '0.8 kg of R-410A' and stopping there, or multiplying by the wrong GWP (using R-22's 1810 for an HFC blend).
Candidates memorise GWP values as isolated numbers and never rehearse the two-step calculation (kg × GWP ÷ 1000 = tonnes CO2e), and they mix up single-component and blend figures under exam pressure.
What to do instead
Drill the formula tonnes CO2e = kilograms × GWP ÷ 1000 until it is automatic, and for every practice question write the refrigerant, its GWP and the CO2e total on the same line. Check the current F-gas GWP table rather than recalling from memory.
Describing the HFC phase-down as a ban on using or servicing R-410A, or stating that reclaimed refrigerant is treated the same as virgin gas under the quota.
News headlines and shorthand talk of 'F-gas bans' blur the distinction between the CO2e quota on placing gas on the market and the separate servicing restrictions that apply only above specific charge and GWP thresholds.
What to do instead
Learn the three separate mechanisms as a list: the phase-down quota (measured in tonnes CO2e placed on the market), the servicing ban on virgin high-GWP gas above a charge threshold, and the rules on reclaimed or recycled gas. Revise the thresholds and dates from the regulation text, not from memory.
Connecting a regulator to a refrigerant or nitrogen cylinder without first checking the hydrostatic test date, valve condition and whether the cylinder has a correct valve cap fitted.
Candidates focus on the task they are about to do and treat the cylinder as a passive object; test-date stamps are small, faint and easily overlooked, and exam scenarios rarely remind you to look.
What to do instead
Adopt a fixed pre-use sequence you can recite: check the test date is in date, check the valve and thread are undamaged, confirm the correct regulator and hose for that gas, secure the cylinder upright, then open the valve slowly. Practise this order until it is a habit.
Treating an A2L refrigerant such as R-32 or R-454B as if it were non-flammable - no ignition-source control, no gas detection, no consideration of room volume or lower flammability limit.
A2L is 'lower flammability' and many candidates remember only that it is 'not as bad as A3', which collapses into 'not flammable' in their notes and in their answers.
What to do instead
Keep a three-way comparison in your revision: A1 non-flammable, A2L lower flammability with a slow flame speed, A3 higher flammability. For A2L, always state ignition-source exclusion, ventilation or room-volume checks, leak detection and appropriate tooling as part of the answer.
Recording a leak check as simply 'checked, no leaks' without the date, refrigerant type, charge size, method used, result and the engineer's name and certification number.
Candidates answer the technical question and treat the paperwork as an afterthought, so they recall that a record exists but not which fields make it compliant.
What to do instead
Memorise the record as a checklist of fields - equipment identifier, date, refrigerant and charge, CO2e, check method, result, any repair and follow-up date, engineer and company details. Write the list out from memory in every revision session until it is complete in one pass.
Applying a single leak-check interval to every system, such as stating that all equipment must be checked every 12 months regardless of charge size or leak-detection fitment.
The frequency table is a set of thresholds with exceptions, and candidates often remember one row of it and generalise; hermetic sealed systems and fitted leak-detection systems add further variations.
What to do instead
Build a table from memory with the charge bands in tonnes CO2e, the corresponding interval, and two modifiers: hermetically sealed equipment and the presence of a functioning leak-detection system. Test yourself by covering the intervals column and reconstructing it, then check against the regulation.
Using a vacuum as the leak test - pulling the system down to roughly -1 bar gauge, seeing the gauge hold, and declaring the system leak-free.
A standing vacuum test is quick, requires no nitrogen, and appears to prove the circuit is sound, so candidates conflate 'holds vacuum' with 'pressure-tight' and skip the pressure test entirely.
What to do instead
Separate the two tests explicitly in your answers: a pressure test with oxygen-free nitrogen proves strength and tightness under positive pressure, and evacuation removes moisture and non-condensables. Never describe vacuum decay as a substitute for a pressure test.
Pressure-testing a system with compressed air or oxygen, or connecting an unregulated nitrogen cylinder directly to the circuit and letting full cylinder pressure into it.
Candidates know nitrogen is the right gas but do not internalise why, so under a scenario requiring an alternative they reach for the workshop air line, and they underestimate how high a full nitrogen cylinder's pressure is.
What to do instead
State the reason, not just the rule: oxygen supports combustion and oil in the circuit can ignite, and compressed air introduces moisture. Always specify oxygen-free nitrogen through a regulator set to the test pressure, with the pressure increased in stages and never above the manufacturer's figure.
Recovering refrigerant into a disposable cylinder or filling a recovery cylinder without weighing it against the 80% maximum fill limit.
Recovery is often taught as a plumbing exercise and the cylinder constraint is treated as a minor detail, so candidates picture any empty cylinder as suitable and forget that liquid expansion leaves no headroom.
What to do instead
Link the rule to the risk: liquid refrigerant expands with temperature and a cylinder without headroom can rupture hydraulically. Before every recovery, state the tare weight, the cylinder's capacity, the 80% figure and the fact that only dedicated, in-test recovery cylinders are used.
Recording the recovered quantity as a rough estimate, or failing to account for refrigerant left in oil, in the receiver or isolated in a part of the circuit during decommissioning.
Candidates treat recovery as done when the machine stops pulling gas, forgetting that residual refrigerant in compressor oil, liquid lines and isolated sections still counts and must be captured and recorded.
What to do instead
Answer with a sequence: isolate and recover from each section in turn, use a recovery machine capable of pulling a deep vacuum, account for gas dissolved in oil, weigh recovered refrigerant, and record the amount against the original charge with any discrepancy explained.