THE USUAL SUSPECTSHumidity issues first appeared in the typical problem areas: the commercial kitchen, hair salon, and a couple of heavily used community rooms. This led to concerns that the humidity could contribute to mold formation.
Eventually, it became clear that the energy recovery system was being called upon to perform in a way that it was not designed to work. Barclay Friends eventually hooked up with Total Services Inc. and a local Desert Aire rep firm, Air Tectonics.
"Outside air was being pulled in raw, and it was being run through an energy recovery wheel, which would transfer energy from the outside air to the exhaust air thus reducing the cooling equipment's load," said Jim McCoy, owner of Air Tectonics. While the energy wheels and existing HVAC system adequately fulfilled the building's cooling needs, McCoy said it was not designed to address outdoor air dehumidification.
The building uses a valence cooling system, which consists of a cold pipe that runs around the perimeter of the room and is protected by a trough to collect condensation. "Air was being introduced at a higher dewpoint than the valence cooling system, so it not only was condensing on the pipes but the walls as well," added Len Wood, president of Total Services
"The [existing] system is a good unit and can do some of the work," he continued, "but over time the building had hit its saturation level and there's no way to get that moisture out."
"There was temperature control but not humidity control," McCoy stated. "The system wasn't designed to do that - therefore, it could be 75°F outside and pouring rain, and thus the air being brought in was very humid but at the desired temperature." As a result, the system successfully met the target temperature but it did not address the humidity.
DEHUMIDIFICATION SYSTEM PAIRS UPTo address the problem, eight Desert Aire VerticalAire™ units were paired with the existing units. McCoy knew that the ductwork was properly sized to bring in the ASHRAE-mandated amount of outdoor air. "We wanted to match the original HVAC design of what the air quantities were expected to be," he stated. In matching the units, six 8-ton VerticalAire units deliver the 1,600 cfm supply air from six original units and provide a leaving air dewpoint of 50.2°. A 15-ton VerticalAire unit delivers its 3,000 cfm of fresh supply air at a leaving air dewpoint of 48.9°, and a 20-ton VerticalAire unit delivers the 4,200 cfm of fresh supply air at a leaving air dewpoint of 49°.
Desert Aire's VerticalAire units were selected because its smaller footprint fit within the tight quarters. It took four-and-a-half months to squeeze the units into close proximity with the current equipment.
James Wright, vice president of Total Services, coordinated the bulk of the retrofits. To avoid interfering with residents lives, he and his crew worked around their normal daily schedules.
"When the residents were in the dining room we knew we had about an hour and 15 minutes of time to get an activity completed that could be disruptive to their daily living," said Wright.
Once the revamped system was operational, Hanson said everyone immediately noticed an improvement. "Our Barclay Friends community now has a comfortable temperature and humidity system to match our warm, home-like-feeling."