White Papers
White Papers
Technical papers on continuous capacity modulation for DX HVAC, from the mechanism behind the APR Control to measured part-load dehumidification and independent, third-party research. Each is a readable page with the full PDF available to download.
Technical white papers
Mechanism
Why the APR Control Is Not Hot Gas Bypass
Instrumented R-410A and R-454B testing of the mechanism: diverted gas returns desuperheated at 67 to 86°F against 125 to 200°F discharge, and the treated compressor unloaded in all 24 matched pairs. Why the label matters for specification and code review.
Humidity
Why the APR Control Improves Dehumidification
Runtime, not tonnage, decides moisture removal. Psychrometric chamber testing showing moisture removal continues throughout modulation, no resolvable latent penalty when full capacity is demanded, and measured capacity reduction corresponding to up to 1.60× the runtime.
External control
How the APR‑E Provides Continuous Capacity Modulation
Field evidence across two controller architectures: stage transitions falling from 11.0 to 1.0 per day on a 150-ton rooftop retrofit, BAS-commanded VPD control in a cultivation facility, and ±1°F discharge air in ASHRAE RP-1604.
Field studies & independent papers
Field study
Virginia Healthcare Field Study
A 3-month independent side-by-side field study: 77% fewer compressor starts (951 to 218), ~53% RH held all summer, zero failures since install.
Co-marketing study
Stratus Cultivation Facility
Field trendlog data from a licensed grow facility: the APR‑E Valve on discharge-air control held ±0.88°F, a 0.128 kPa VPD range, and ±1.5% RH on standard split-system DX. Written up as a case study, with the full PDF to download.
Independent (York/JCI)
Capacity Modulation Comparison
An independent York/JCI white paper comparing capacity-modulation methods for rooftops, including hot gas bypass, Rawal APR valves, digital scroll, and inverter scroll.
Want to talk it through?
Tell a Rawal Devices Engineer about your equipment and application, and sizing is on us.
Get Expert Help[email protected] · 800‑727‑6447 · rawal.com