On the campus of Rockingham Junior High School in Rockingham, N.C., where hot and humid weather is common during spring, summer, and fall, buildings are heated and air-conditioned with unit ventilators and fan-coil units connected to a two-pipe hot-water or chilled-water system. During cooling season, chilled water is produced by an air-cooled chiller; during heating season, hot water is produced by a gas-fired boiler. All ventilation is provided through the unit ventilators, which are connected to the outdoors.
For a three-story classroom addition, Richmond County Schools wanted an HVAC system that complemented and supported the existing HVAC equipment and avoided the severe mold and mildew problems newly constructed schools in the area were experiencing because their mechanical ventilation systems did not treat outdoor air independently.
The district installed two Greenheck ERCH energy-recovery units — one 7,500 cfm, the other 7,900 cfm.
With the ERCH units, chiller capacity was reduced by 36 tons, while boiler capacity was reduced by 129 Mbh. Additionally, a unit ventilator serving a typical classroom was downsized to 1,000 cfm of supply air; a classroom unit ventilator conditioning outdoor air directly would have had to been sized at 1,500 cfm. What's more, the cooling-load requirement of a typical classroom was reduced by more than 1.5 tons. Additional cost savings were achieved through the installation of a smaller hydronic piping system, which was made possible by the energy recovery units' reduction of system gallons per minute by an estimated 25 percent.
After one year of operation, the school's principal said he was very pleased with the indoor-air quality provided by the HVAC system.
Greenheck Fan Corp.
P.O. Box 410
Schofield, WI 54476-0410