Leak rate: the annualizing method and the rolling average

The appliance

A walk-in cooler on R-404A with a full charge of 42.0 pounds, determined from the nameplate (84.102, full charge, method 1). The contractor added 4.0 pounds on 26 April, the first addition since 1 January 2026, and 9.5 pounds on 4 September, 131 days later. Commercial refrigeration, so the applicable leak rate is 20 percent (84.106(c)(2)(i)).

The annualizing method

Four steps (84.102, leak rate, method 1). Step one: pounds added to return the appliance to full charge, divided by the full charge. Step two: the shorter of the days since the last addition or 365, divided by 365. Step three: the first result divided by the second. Step four: times 100.

The April addition was the first since the rule took effect, and for a first calculation the rule says to substitute 365 days (84.106(b)(1)), which makes it 4.0 ÷ 42.0 × 100 = 9.5%. The September addition annualizes a 22.6 percent loss over 131 days into 63.0% a year, three times the limit. The repair clock starts on 4 September.

The rolling average

Three steps (84.102, leak rate, method 2). Step one: the sum of the pounds added over the previous 365 days, or since the last successful follow-up verification test if that is more recent. Step two: divided by the full charge. Step three: times 100. For the first calculation after 1 January 2026 the sum is the pounds added since that date (84.106(b)(2)).

Same appliance, same two additions, 32.1% instead of 63.0%. Still over 20 percent, so the clock starts either way; on a smaller top-up the two methods can land on opposite sides of the limit.

Why they differ, and why you keep one

The annualizing method looks at the latest addition and stretches its pace over a year, so a large top-up soon after the last one reads as a fast leak. The rolling average looks at everything added in the window, so it smooths a single event and catches a slow drip that never trips the annualizing test. Neither is more correct; the rule offers both and then requires that the same method be used for all appliances subject to leak repair at an operating facility (84.102), with a switch allowed only after acquiring a facility that used the other one (84.106(b)(3)). Whichever you keep, the service record carries the rate and the method (84.106(l)(2)).

Two things the arithmetic needs on file: the full charge and how it was determined, and the date of the previous addition. Hand-kept records lose the second one first. The calculator runs the annualizing method on numbers you type; the ledger computes both from the entries on the day the addition is logged.

Common questions

Can I switch methods?

Only in the case the rule names: after acquiring a facility that used the other method, and only if no appliance at the facility exceeds the limit under either method, with a record of the change (84.106(b)(3), (l)(3)). Otherwise the facility keeps one method for all its appliances (84.102).

What if refrigerant was added more than a year ago?

The annualizing method takes the shorter of the days since the last addition or 365, so a gap longer than a year counts as a year and the rate equals the share of charge added. The rolling average sums only the additions in the previous 365 days.

Which method does the ledger use?

The free calculator runs the annualizing method. The ledger recomputes every card from its entries and carries the method on each record, since 84.106(l)(2) requires the method to be recorded with the rate.