System Type
VAV & VVT Systems
Variable air volume (VAV) and variable volume & temperature (VVT) systems vary airflow to match zone load, but airflow alone cannot match the cooling load. Rawal Devices modulates refrigeration capacity to the actual load, so the equipment follows the space.
Mechanical or electronic
A VAV or VVT system can use either the mechanical APR Control or the electronic APR‑E Valve. The right choice depends on how precise the discharge-air temperature must be to satisfy the job's conditions, which is exactly why you should talk to a Rawal Devices Engineer for the selection.
Why VAV & VVT
VAV and VVT systems, including single-zone VAV (SZVAV), change-over bypass, and zone-damper systems, throttle airflow to each zone as loads change, but airflow alone cannot match refrigeration capacity to the load. As airflow drops, the coil is still trying to deliver full capacity, and the mismatch shows up four ways, made worse by erratic occupancy.
Short Cycling
The compressor cycles on and off because capacity cannot follow the reduced load.
Coil Frosting
At low airflow the evaporator coil can frost or ice, starving the system.
Hot & Cold Spots
Discharge-air temperatures swing, leaving inconsistent comfort across zones.
Rising Humidity
Runtimes are too short to dehumidify, so space humidity climbs.
How Rawal Devices Helps
Instead of relying on airflow reduction alone, the APR Control modulates the system's refrigeration capacity to the actual load, true load matching. The compressor keeps running at part load, the coil stays above freezing, runtime extends for dehumidification, and the need for reheat drops.
A proof point in the field
A single-zone VAV system in a New Hampshire TV-station newsroom had discharge air dropping below design, coil icing, and condensation on the floor, and the space needed whisper-quiet operation. An APR Control retrofit delivered variable capacity similar to a chilled-water option at a fraction of the cost.
Zoned System Energy
On zoned, zone-damper installations, continuous modulation holds each zone steadier at part load. The system runs longer at reduced capacity instead of cycling, so it keeps delivering useful cooling instead of overshooting and shutting off.