How do you calculate coil test pass rate?

Divide coils passed by total coils tested. With 243 passed of 250 tested, the pass rate is 243 divided by 250, or 97.2%.

What is a good pass rate for coil leak and drain testing?

A healthy coil line typically runs 96-99% first-time pass. The example's 97.2% slightly beats a 97% target, a 0.2-point cushion, which is a clean line.

What does a negative gap to target mean here?

The gap is target minus actual, so a negative value means you exceeded the target. Here 97% target against 97.2% actual gives a -0.2-point gap, meaning the line is just above plan.

What causes coils to fail leak and drain testing?

Leak failures usually trace to braze voids, cracked U-bends, or loose return-bend joints. Drain failures come from incorrect pan slope, blocked weep paths, or fin pack debris holding condensate.

Should I separate leak failures from drain failures?

Yes. This rate combines both, but they have different root causes, braze quality versus assembly geometry. When the rate dips, split the failures so you fix the right station.

How many coils should I plan to test to ship 243 good ones?

At a 97.2% pass rate, you'd test about 250 coils to clear 243, matching the example. If pass rate slips to 95%, you'd need to test around 256 to ship the same 243.

HVAC Ductwork, Air Handling & Mechanical Products calculator

AHU Coil Leak and Drain Test Pass Rate Calculator

Coil Drain Rate tracks the share of HVAC coils that pass leak and drain testing, the gate that confirms a finished coil holds pressure and clears condensate without trapping water. Coil-line quality engineers and test-stand operators use it to monitor braze and tube-joint integrity batch by batch. It matters because a coil that fails in the field means a warranty claim, a flooded drain pan, or an air handler down, so the test-stand pass rate is an early warning on braze quality and pan-slope assembly. Comparing the pass rate to an acceptance target tells you instantly whether the coil line is running clean.

What this calculator does

Calculate the coil leak test and drain pan test pass rate for chilled water, hot water, or DX coils in air handling unit production. Compare tested coils that pass to total coils tested and check the gap against your quality acceptance target.
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.
It computes the percentage of tested coils that passed leak and drain testing and the point gap to your acceptance target.

Formula used

Coil test pass rate = coils passed ÷ total coils tested
Gap to target = target pass rate - calculated pass rate

Inputs explained

Coils that passed leak and drain test:
Total coils tested:
Acceptance pass rate target:

How to use the result

Use it per batch or per shift to monitor coil test-stand pass rates and catch a braze or assembly problem early.
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.

Current U.S. benchmarks

Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.
U.S. housing starts run at 1,177k per year (Census, May 2026), down 8.7% from a year earlier, the demand driver for building products.

Common questions

How do you calculate coil test pass rate? Divide coils passed by total coils tested. With 243 passed of 250 tested, the pass rate is 243 divided by 250, or 97.2%.
What is a good pass rate for coil leak and drain testing? A healthy coil line typically runs 96-99% first-time pass. The example's 97.2% slightly beats a 97% target, a 0.2-point cushion, which is a clean line.
What does a negative gap to target mean here? The gap is target minus actual, so a negative value means you exceeded the target. Here 97% target against 97.2% actual gives a -0.2-point gap, meaning the line is just above plan.
What causes coils to fail leak and drain testing? Leak failures usually trace to braze voids, cracked U-bends, or loose return-bend joints. Drain failures come from incorrect pan slope, blocked weep paths, or fin pack debris holding condensate.
Should I separate leak failures from drain failures? Yes. This rate combines both, but they have different root causes, braze quality versus assembly geometry. When the rate dips, split the failures so you fix the right station.

Last reviewed 2026-05-12.