case in point: Texas Denny's restaurant takes humidity off its menu
December 1, 2006
Scientifically speaking … evaporation is the change of a liquid into vapor at any temperature below its boiling point. For Alvie Britton, quicker evaporation means higher profits. Britton, the owner of four Denny’s franchise restaurants in south Texas, explained, “It’s simple: the quicker a table dries after it’s wiped down, the sooner we can seat another customer.”
On weekends, Britton’s busy restaurants shoot for 30- to 40-min table turns. According to Denny’s mandated franchise sanitary practices, tables are sprayed, wiped, and allowed to air dry. Faster table drying time was a welcome side benefit of a solution to a problem Britton was experiencing at his Brownsville, TX location.
Tropical TexasAbout three years after the store was opened in January 2001, the Brownsville Denny’s was suffering from humidity problems. Brownsville is as far south as Miami and located on the Gulf of Mexico coast, so tropical humidity can be a problem for building air quality.
“We were experiencing severe problems,” Britton said. “The store had a dank, musty feel to it - it was always damp. We’d shampoo the carpets and it would be two days before they’d really dry out.” In addition, the vinyl wallpaper was peeling off the walls and there were problems with mildew.
“We did pull off all the wallpaper and repainted the walls,” Britton said. “That was a big plus, but we still had that dank smell and feel that we wanted to get rid of.”
Getting Local ExpertiseTo address this problem, Britton reviewed an HVAC proposal from a local company that understood the existing climate issues and provided a more suitable recommendation. First, they suggested that the foyer and seating area be positively pressurized. This would ensure that as customers entered from the front, hot and humid air wouldn’t infiltrate the restaurant and stream toward the kitchen to exit via the exhaust hood.
The second recommendation the firm proposed was to install a hybrid desiccant-refrigeration dehumidification unit to dry out the 100% outdoor air that was required for pressurization. The firm also said that this system could replace one of the packaged rooftop units originally specified to provide cooling.
After further investigation, Britton learned that while this desiccant-DX system would handle the latent load, it could not provide air cool enough to contribute to the cooling requirements of the space. The resulting uncomfortably warm environment would deter his customers from staying or returning to Denny’s. To treat the air, he faced having to retain the A/C unit, which the dehumidifier was to replace.
Determined to solve both his humidity and temperature problems, Britton then contacted local HVAC contractor, McAllen Refrigeration, which connected him with Eric Johnson, P.E., of Paschal-Harper, San Antonio, TX. Johnson reviewed the previous plans and agreed with pressurizing the restaurant.
Johnson, however, proposed using a Desert Aire refrigeration-based TotalAire™ dehumidifier in favor of the desiccant-DX system that was previously suggested. He determined that the TotalAire unit would provide full dehumidification while also providing a significant portion of Denny’s cooling needs.
Britton adopted Johnson’s recommendation to install a TotalAire 15-ton dehumidifier at the Brownsville store. As a true DOAS unit, TotalAire is specifically designed and built to treat 100% outdoor air for excess humidity and high temperatures. The system’s patented refrigeration design delivers dehumidified air at precise leaving air temperatures within ±0.2° F.
A Positive Turning Of The TablesAs it turns out, the TotalAire 15-ton dehumidifier was able to provide all of the cooling capacity needed for pressurization at the Brownsville store and therefore completely replaced the existing 12-ton packaged rooftop unit. However, Britton was able to use this 12-ton unit at a new Denny’s restaurant he was building.
A side benefit from this HVAC solution was that a smaller makeup air supply fan was needed for the kitchen. By code, outdoor air must also be supplied to the kitchen. The new design that combined pressurization with the TotalAire unit was able to deliver more dry, 100% outdoor air to the kitchen, thus reducing the size of the supply air fan.
Britton reports that his sales at the Brownsville location are up 12% over last year since the dehumidification system was installed. “The crew is happier, the management is happier and the A/C vents aren’t dripping water like they had been. Now when we clean the carpets, they dry by the time we have a meal crunch, and the tables dry faster, increasing our table turn,” Britton concluded.