Compressor Short-Cycle Protection
Estimated cycles per hour from the ASHRAE/AHRI part-load cycling parabola, on/off time, and the minimum oil-return runtime and pressure-equalization delay by system type, flagging oversized single-stage short-cycling. Per Copeland AE Bulletin 17-1226.
Formula and source
Cycle rate N = N_max × 4 × X × (1 − X), where X is the runtime (load) fraction and N_max is the per-hour ceiling; the parabola peaks at X = 0.5. On-time = X × 60 / N; off-time = (1 − X) × 60 / N. Short-cycling is flagged when the estimated on-time is below the minimum oil-return runtime or the observed cycles exceed the ceiling.
Copeland Application Engineering Bulletin 17-1226 by name; ASHRAE Fundamentals 2021. The ASHRAE/AHRI part-load cycling model by name.
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