Leak rate

Leak rate is the measure of how quickly an appliance is losing refrigerant, expressed as a percentage of its full charge on an annualized basis. It is the trigger metric for the leak repair framework: for appliances with a full charge of 50 or more pounds of a class I or class II (ozone-depleting) refrigerant, exceeding the applicable threshold creates repair obligations for the owner or operator. Appliances charged solely with substitute refrigerants sit outside the leak repair section. The thresholds depend on equipment class: 20 percent for commercial refrigeration, 30 percent for industrial process refrigeration, and 10 percent for comfort cooling and other appliances.

The regulation allows two methods and no others: the annualizing method, which takes the refrigerant added to return the appliance to full charge, divides by the full charge, and scales by the days since the last addition, and the rolling average method, which sums the additions over the previous 365 days and divides by the full charge. Neither is a lifetime average. A shop that divides all refrigerant ever added by the appliance's age will understate the leak rate of a system whose condition is deteriorating, because early tight years dilute recent losses. Both permitted methods reflect the appliance's current behavior, which is what a repair obligation is meant to address. Purged refrigerant destroyed at 98 percent or greater verified efficiency may be excluded from the calculation.

Above the repair thresholds sits a disclosure obligation: an appliance that leaks 125 percent or more of its full charge in a calendar year requires a report to EPA. A system can exceed its own full charge in a year because it is repeatedly topped off as it leaks. On the exam, leak rate questions hinge on classification, on the rolling versus lifetime distinction, and on matching each number to its obligation.

Common questions

Sources

• Leak repair requirements and calculation methods: 40 CFR 82.157.

Related terms