HVAC Equipment Right-sizing: Occupant Comfort and Energy Savings Potential

ABSTRACT ABSTRACT HVAC equipment uses a significant amount of electricity and affects occupant comfort. In recent years, ventilation code requirements have often driven the size of the equipment upward, resulting in mismatched cooling capacities. Oversized cooling equipment will experience shorter run cycles, which reduces the ability to dehumidify air and reduces the life span of the equipment. Increased humidity levels can lead to mold conditions, resulting in building damage and occupant health issues. It is important to correctly match cooling capacities with the real load requirements of a facility, as this will reduce costs and increase comfort. Facilities undergoing capital renewal HVAC renovations were evaluated for energy saving opportunities. For facilities that had been experiencing combined high humidity and energy usage, revised load calculations were performed to correctly size the equipment. (Load calculations need to be performed twice: once to size the air handling units for code required ventilation quantities and once to place the real ventilation load on the cooling systems.) Consideration was also given to part-load conditions on equipment so that multiple compressors could be provided to match load conditions that were lower than peak design. A case study shows an example of a failed renovation resulting in excessive humidity levels. Load calculations were performed for subsequent renovations to prevent this situation from occurring again, and this resulted in improved energy performance and lowering of humidity levels, as demonstrated in successful case studies. There is increased acceptance of this practice, which is reinforcing the need for right-sizing of equipment in new facilities rather than just renovations. Right-sized equipment reduces first cost, extends life span of equipment and future replacement costs, reduces energy use, and improves occupant comfort.