Recovering R-410A After a Coil Leak in a Plant Room
You are a third-year apprentice sent with a licensed technician to a small supermarket plant room holding three R-410A condensing units. Unit 2 has a leaking evaporator coil; the technician isolates it and recovers the charge. The plant room is below ground with no mechanical ventilation, a single doorway, and a floor drain connected to the sewer. Ambient temperature is 31 °C and the room is humid. The recovery cylinder is a 12 kg DOT-style cylinder currently holding 4 kg of recovered R-410A, and its stamped tare weight is 8.5 kg. As recovery begins the technician says he will 'just crack the valve and let the last bit go' because the cylinder is nearly full and the schedule is tight. You also notice the recovery machine's hose has a Schrader depressor that is not sealing and a small hiss at the connection.
1. Assess whether the recovery cylinder has capacity for the remaining charge, and explain the safety and environmental consequences of the technician's proposal.
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First establish the cylinder's allowable fill. Recovered refrigerant is filled by weight, not volume, and the common working limit for recovery cylinders is 80% of the water capacity by weight. The stamped tare is 8.5 kg and the cylinder is rated 12 kg, so the gross allowable weight is 0.80 × 12 = 9.6 kg, meaning the maximum net refrigerant is 9.6 − 8.5 = 1.1 kg. The cylinder already holds 4 kg, which is already well past that limit - so the cylinder is overfilled now, not 'nearly full'. The correct action is to stop, use a second correctly sized cylinder or a larger one, and reweigh. Venting the remainder is unlawful in most jurisdictions under ozone/fluorinated-gas rules and is never a substitute for capacity planning; R-410A is a high-GWP HFC blend and releasing it is both a compliance breach and a personal exposure risk in an unventilated basement. The leaking hose connection adds a second problem: a non-sealing depressor admits air and moisture into the recovered charge and creates an asphyxiation/leak point in a confined space. The response is to stop work, repair or replace the hose, ventilate or use gas detection before continuing, and record the recovered quantity. R-410A is heavier than air and will pool at the drain, so the drain is not a safe discharge path.
2. Describe the confined-space and electrical controls you would expect before recovery proceeds, and how you would raise your concerns on site.
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The plant room meets the classic confined-space profile: below ground, limited entry, no mechanical ventilation, and a potential IDLH atmosphere from refrigerant pooling. Before entry there should be a documented risk assessment, atmospheric testing (oxygen and refrigerant detection) at the low point near the drain, a standby person outside the doorway, and a rescue plan that does not rely on the entrant self-rescuing. Because refrigerant displaces oxygen, the low-level reading matters more than the reading at head height. Electrically, recovery machines and vacuum pumps should be on a residual-current device, leads should be inspected, and no work should occur on live control circuits; the unit should be locked out and tagged at the isolator. On the human side, raising a concern about an overfilled cylinder and a venting plan is a legitimate stop-work trigger. I would state the specific facts - the weight calculation, the leaking hose, the lack of ventilation - ask the technician to pause, and escalate to the supervisor if the practice continues, because 'the schedule is tight' is not a defence under WHS law and the apprentice shares the duty to not proceed with unsafe work.