HVAC Ductwork, Air Handling & Mechanical Products worked example

Coil Drain Rate at 99% acceptance pass rate target: a worked example

What does the result look like when acceptance pass rate target reaches 99%? The full calculation is worked below with real intermediate numbers. Use this when tracking leak test acceptance rates on chilled water coils, hot water coils, or DX refrigerant coils during AHU assembly. Each coil must pass a hydrostatic or pneumatic pressure test before it is installed in the casing. Tracking the pass rate identifies trends in brazing quality, tube expansion consistency, or incoming coil defect rates from suppliers.

The inputs for this scenario

  • Coils that passed leak and drain test: 243 coils (unchanged)
  • Total coils tested: 250 coils (unchanged)
  • Acceptance pass rate target: 99 % (raised for this scenario; the documented default is 97)

Working through the calculation

  • Applying the documented formula (Coil test pass rate = coils passed รท total coils tested) to the inputs above produces each figure below.
  • At this operating point the engine returns 97.2 % for rate, the number this scenario is built around.
  • At this operating point the engine returns 1.8 points for gap to target.
  • At this operating point the engine returns 243 count for affected count.
  • At this operating point the engine returns 250 count for total count.

How this compares with the baseline

  • Against the tool's baseline example, where acceptance pass rate target sits at 97% and the headline result is 97.2 %, this scenario lands almost exactly on the baseline at 97.2 %.
  • A figure at this level is achievable when acceptance pass rate target is genuinely sustained, not just peaked for a shift. It is a pass/fail count and does not distinguish a pinhole leak from a slow-drain reject, so dig into the failure reasons when the rate dips.

Results at a glance

  • Rate: 97.2 % (headline result)
  • Gap to target: 1.8 points
  • Affected count: 243 count
  • Total count: 250 count

Run it with your numbers

  • Every input above is editable in the live Coil Drain Rate calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.