Run Capacitor Microfarad Check

The in-circuit capacitance of a motor run capacitor from the measured volts and amps (C = I / (2 x pi x f x V) at 60 Hz, the ~2652 x amps / volts field rule) compared to the nameplate rating and an editable +/-6% tolerance band, with a good / weak / replace verdict.

measured_uf = 1e6 x I / (2 x pi x 60 x V) ~= 2652 x measured_amps / measured_volts (the in-circuit capacitance from Xc = 1/(2 x pi x f x C) at 60 Hz). Band = rated_uf x (1 +/- tolerance%/100); within / below / above gives the good / weak / replace verdict.

First-principles capacitive reactance (public); +/-6% run-capacitor tolerance is the common motor-capacitor convention (by name).

The capacitive-reactance relation is public physics; the tolerance is an editable field convention.

Estimate. AHJ and licensed professional govern.

Field names used by the API: rated_uf, measured_volts_V, measured_amps_A, tolerance_pct, measured_uf, pct_of_rated, low_uf, high_uf

• Frequency 60 Hz line frequency (the 2652 constant is 1e6 / (2 x pi x 60))first principles
• Tolerance default +/-6% for run capacitors (editable); start capacitors use a wider bandmotor-capacitor convention
• Measurement amps by clamp on a capacitor lead and volts across its terminals with the unit running; replace with equal microfarad and equal-or-higher voltage ratingfield practice