Ramez Afify of E4P consulting engineering discusses the fundamentals of Air Cooled VRF design.
VRF systems offer controls that match the space heating/cooling loads to that of the indoor coil over a range of operation. Variable speed compressors and fans in the outdoor units modulate their speed, saving energy at part-load conditions. Outdoor sections should be sized to match building peak loads, not the sum of the peak load for each zone, reducing the capacity of outdoor units when compared to a conventional unitary system. The system offers designers and occupants the ability to choose multiple individualized zones, which improves system controllability. The system capabilities and limitations should be evaluated carefully to determine the suitability of the VRF for a project and to optimize its design.