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ACCA
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PDF export
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$2.99 Pro
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How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact ACCA reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
Run and start capacitors keep HVAC motors turning. When one drifts out of tolerance the compressor or fan motor struggles, draws high amps, and eventually fails. This app helps you check a capacitor against its rating and pick the right replacement by microfarads and voltage.
What matters in a capacitor
- Capacitance (µF) — must match the motor rating; run capacitors are typically held to about ±6% tolerance.
- Voltage rating (VAC) — use a replacement rated at or above the original (370 V can be replaced by 440 V, not the reverse).
- Dual-run capacitors — one can carries both HERM (compressor) and FAN values; both must be in spec.
Worked example
A 45/5 µF dual-run capacitor measuring 41 µF on the HERM terminal is more than 6% low (45 × 0.94 = 42.3), so it is out of tolerance and should be replaced even though the motor still starts.
Related calculators
Check the equipment circuit with the HVAC electrical calculator and diagnose performance with the superheat and subcooling calculator.
Capacitor FAQ
How much tolerance does a run capacitor have?
Run capacitors are commonly rated to about ±6%. A reading outside that band means the capacitor is failing and should be replaced with the rated value.
Can I use a higher voltage capacitor?
Yes. You may replace with an equal or higher voltage rating — for example a 440 V can in place of a 370 V — but never a lower voltage. The microfarad value must match.
What is a dual-run capacitor?
A single can with two ratings, such as 45/5 µF, that serves both the compressor (HERM) and the fan motor (FAN). Both sections must be within tolerance.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
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