Packaged unit's dehumidification teaches Texas junior high how to quiet complaints
"We were getting a lot of complaints about air quality in the school," says Scott Porter, Richardson Independent School District (RISD) hvac maintenance manager. "We were not meeting ASHRAE standards. Some classrooms were freezing cold and others were hot and humid. There were a lot of problems."
"Clamminess" ControlMany of the climate and IAQ problems emanated from the 25-year-old, worn-out units, which were installed when the school was first constructed. The units were all single-zone rooftop units with no dehumidification system or device and needed replacing. RISD decided to evaluate the situation using a humidity-control unit.
"Most of the air quality complaints revolved around the building being too cold to reduce humidity or too clammy from too much humidity," says Porter. "The solution we considered was new rooftop units with a dehumidification device. We needed outside air introduced to the building while at the same time we needed to stop the humidity and irregular indoor climates altogether."
"We used a model competitive with the Humiditrol in some of the other RISD schools," says Porter. "But we weren't getting the dehumidification out of it like we had expected. We had uneven heating and cooling and had to adjust the units several times to optimize the climate. When trying to dehumidify with that unit, it cooled the classrooms too much."
Management at the district was attracted to the Humiditrol option on the L Series(r) packaged units (from Dallas-based Lennox) because it can provide dehumidification on demand without a call for cooling from a space thermostat, which provides maximum moisture removal at virtually any outdoor temperature. RISD purchased 47 L Series units with the Humiditrol option for Parkhill Junior High School to meet its cooling and air quality needs. "We went with Lennox because of the Humiditrol unit's features and the results we could achieve with it," says Porter.
More Bodies = More HeatAllied Mechanical, a contractor in Richardson, Texas, installed the 47 Humiditrol units in August 2001. Tonnage for the replacement units was increased, since today's classrooms differ from the classrooms 25 years ago. "Today, classrooms have about five to six more students in them, and they also have at least eight computers in each classroom," says Porter. "We had to increase the tonnage for more cooling and to bring in more outside air."
In the beginning, thermostats were installed to maintain the new hvac system, but eventually, the Energy Management System from Andover Controls (Andover, MA) replaced the temporary thermostats. "The Energy Management System controls humidity, and we're able to program it with our specifications," says Porter. "We have subcontrollers in each individual unit with one main controller in the building. This controller basically allows us to regulate correct temperature, and if we get temperature complaints, we can go to the one panel to determine the problem."
The only other issue after installation concerns the return air ducts. The way the ducts are situated allows more return air than desired at times, but now RISD hvac maintenance is working to relocate these ducts and install spring-loaded dampers, so the return air ducts are only open when the unit is running.
"A Tremendous Difference"Parkhill Junior High has already noticed changes. The building's systems are now meeting ASHRAE standards, maintaining even temperatures throughout the building, and achieving humidity removal goals.
"We have noticed a tremendous difference in the school's climate," says Porter. "There is also a uniform climate throughout the building in each classroom, and no humidity problems, which is great, since we've had a lot of cooler and more humid days recently. We're very pleased with these units. We're anticipating energy savings. Even though we've increased our unit tonnage, our temperatures are more even throughout the building, and we won't have to overcompensate in some areas to cool humid or hot areas anymore." ES