Case Study · Labs & Cleanrooms
ASHRAE Cleanroom Research (RP-1604): Precision Discharge-Air Control
For ASHRAE research project RP-1604, the APR‑E Valve held discharge-air temperature to about ±1°F across ISO Class 1 to 8 cleanrooms while airflow varied on particle count, not temperature.
The Challenge
ASHRAE set out to develop energy-efficient cleanroom standards by testing demand-based ventilation tied to particle counts rather than temperature. A standard 3.5-ton single-stage Trane condensing unit could not hold the precise temperature stability required while airflow varied continuously to maintain ISO Class 1 to 8. Traditional DX simply lacks that modulation range.
The Solution
Engsysco integrated the APR‑E Valve, an electronically controlled external compressor-unloading device, into the lab's controls. It turns the fixed-capacity compressor into a continuously modulating system, so discharge-air temperature control could be integrated with the building management system's particle-counting algorithm.
“Precise discharge air control was much needed. We were able to maintain a deviation from setpoint of no more than ±1°F.”
Wei Sun, P.E. · President of Engsysco and Principal Investigator
The Results
The APR‑E Valve delivered the stability the study needed, and:
- Held discharge-air temperature to about ±1°F from setpoint
- Kept four ISO Class cleanrooms (Class 1 to 8) within spec
- Allowed airflow to vary for demand-based filtration while temperature held
- Produced findings that support new ASHRAE cleanroom energy standards
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