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.

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.

Copeland AE bulletins free at copeland.com/literature; ASHRAE Handbook TOC free at ashrae.org.

Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.

Field names used by the API: system_type, load_fraction_pct, cph_estimated, on_time_min, off_time_min, min_runtime_min

• Cycling parabola N = N_max × 4 × X × (1 − X)ASHRAE/AHRI part-load cycling model
• Single-stage minimum runtime 10 min on, 5 min offCopeland AE Bulletin 17-1226 / industry rule of thumb
• Cycles-per-hour ceiling 6 single-stage, 8 two-stagecompressor-protection guidance