Cold store R-404A: charge, CO2e and leak-check frequency
A regional distribution centre has a low-temperature cold store served by a pumped-circulation R-404A system. The nameplate charge is 130 kg and the GWP of R-404A is 3922. You attend a pressure fault and find the suction-side liquid line joint on the outdoor condensing unit coated in oil. The site log shows three top-ups in the last 14 months: 18 kg, 15 kg and 8 kg. There is no fixed refrigerant leak detection system in the plant room. The site manager says the plant 'runs fine as long as we keep topping it up' and asks you to add another 10 kg, then re-set the frequency of their routine leak inspections to suit.
1. Calculate the CO2-equivalent charge of this system and state the minimum leak-check interval that applies now, and the interval if a compliant fixed leak detection system is installed and inspected annually. Show your working.
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Working
- 130 kg x 3922 (GWP) = 509,860 kg CO2e = 509.9 t CO2e.
Frequency as it stands
- The thresholds are: 5 t CO2e = every 12 months; 50 t = every 6 months; 500 t = every 3 months plus a mandatory leak detection system.
- At 509.9 t the site is just over the 500 t line, so checks are required at least every three months (four a year), and a fixed leak detection system must be fitted and verified at least once every 12 months.
If a compliant LDS is fitted and inspected annually
- The check frequency halves: every six months.
Judgement point
- The result sits barely above the threshold, so the GWP value used must be the one listed in the regulation in force in your country, and the charge must be the nameplate or measured charge, not the cylinder contents. Record the basis of the calculation so the next technician reaches the same answer.
2. The 41 kg of top-ups are on the log. Explain what this tells you, what the operator is legally obliged to do, and what you should do before adding another 10 kg.
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What it tells you
- 41 kg x 3922 = 160,802 kg CO2e, i.e. about 160.8 t CO2e, roughly 31% of the total charge lost in 14 months. That is a system with an unresolved leak, not a system needing routine topping up.
Operator's obligation
- Leakage must be repaired without undue delay. If the repair cannot be done immediately, a documented repair timetable must be in place, and a follow-up leak check is required within one month of the repair being completed.
- Continually adding refrigerant to a known leaker does not satisfy the containment duty, and the top-ups themselves must be recorded.
Your action before adding gas
- Locate the leak first (electronic detector plus oxygen-free nitrogen for confirmation, not a naked flame), record the findings, and put the leak and the operator's obligations to them in writing.
- Adding another 10 kg to a leaking system without a repair plan simply delays the repair and leaves an audit trail that shows repeated top-ups. Refuse to treat the top-up as the solution; offer a repair and a follow-up test.
3. List the records that must exist for this system, who is responsible for them, and how long they must be kept. What certification should you and your employer hold?
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Records (operator-level)
- The type and quantity of refrigerant charged.
- Quantities added, with dates and the reason (e.g. after a leak repair).
- Dates and results of every leak check, including the method used.
- Dates of any leak detection system checks.
- Any recovery or decommissioning, and where the recovered gas went.
- The name of the certified company and the individual who did the work.
Responsibility and retention
- The operator (the organisation with operational control of the plant, here the distribution centre) owns the obligation and must make records available on request. Records are normally retained for at least five years.
Certification
- The company must hold a current F-gas company certificate, and the individual doing the work must hold the appropriate personnel certificate – this work (charge over 5 t CO2e, leak checking, recovery) falls inside Category I.
Judgement point
- A gap in the log does not mean no leak checks were needed; it means the operator cannot demonstrate compliance, which is itself a finding worth reporting.