Leak Repair on a Refrigerated Display Case in a Busy Store
A supermarket refrigerated display case running R-448A has a slow leak. The store is open, and the case holds chilled food that must stay below 5 C. The technician's leak detector alarms near the evaporator, but the exact point is behind a panel that requires the case to be emptied. The system holds 6 kg. The store's maintenance policy says leaks must be repaired within 14 days of detection, but the technician is told the case cannot be emptied until the weekend, five days away. A temporary top-up would keep the case running, and the technician has R-448A available. The circuit has no isolation valves, so any repair means recovering the full charge.
1. Evaluate the proposal to top up now and repair at the weekend, including the effect on the refrigerant and the leak record.
Read the worked answer
A top-up now is a pragmatic way to protect the food, but it has consequences the technician must weigh. Adding R-448A to a leaking circuit does not change the fact that the leak continues, so the top-up buys time rather than fixing anything, and the added refrigerant will largely escape before the weekend. That matters because R-448A is an HFC blend with a significant global warming potential, and every unnecessary gram released works against the environmental objective behind leak control.
The top-up also affects the leak record. The system's charge is now uncertain, so the weekend repair cannot be verified against the original 6 kg figure without accounting for what was added. The technician should record the mass added, the date, and the reason, so the post-repair charge can be reconciled. The 14-day policy is satisfied by a weekend repair, so the timing is compliant, but the technician should confirm the top-up is permitted under the store's policy and that the leak rate does not require faster action. If the leak is fast enough that the case cannot hold temperature, the case must be emptied sooner.
2. Because there are no isolation valves, the weekend repair requires recovering the full charge. Explain the recovery plan and the checks needed before the case is restarted.
Read the worked answer
The plan starts with emptying and isolating the case so the evaporator panel can be accessed, and arranging alternative chilled storage for the food. The technician then connects the recovery machine and a dedicated recovery cylinder, recovers the full charge, and records the mass. Because the circuit has leaked and been topped up, the recovered mass will differ from the nameplate, and the technician should note both figures. The recovered refrigerant is set aside; it should not be returned to the circuit unless its identity is confirmed and it is clean, and given the leak and top-up history, sending it for reclamation is the safer choice.
After the repair, the technician must evacuate to a measured vacuum and confirm it holds before recharging. Recharge is by weight to the corrected figure, and the technician should verify superheat at the evaporator and the case temperature against the food-safety requirement. The leak detector should be run again around the repaired joint and nearby brazed connections. Only when the vacuum holds, the charge is correct, and the case pulls down to temperature should the food be returned.
3. The store manager asks whether the old refrigerant can simply be released because the amount is small. Respond with the technician's reasoning and the alternative.
Read the worked answer
Releasing the charge is not an option. The amount is 6 kg, which is not trivial, and R-448A is a controlled HFC blend with a high global warming potential; deliberate venting is prohibited under refrigerant handling rules regardless of the quantity being small relative to an industrial plant. The technician's obligation is to recover the refrigerant and route it to reclamation or destruction with documentation.
The alternative is straightforward: recover into a dedicated cylinder, label it with the refrigerant identity and mass, and send it to the depot or a reclamation facility. The cost of recovery is part of doing the job correctly, and the store manager should be told that the recovered gas may have reclaim value that partly offsets the cost. Framing the choice as recovery versus venting, with the legal and environmental reasons stated plainly, gives the manager a clear basis to approve the correct course.