With some dehumidification systems, the dehumidifier works in conjunction with the HVAC system and is only online when there is a need for cooling. If a store’s temperature level stays within a desired range, the HVAC equipment does not operate and humidity will not be reduced in the space.

Proper dehumidification is essential to the preparation of doughnuts. “Our glazed doughnut is our signature product, and it’s important that the glaze on that doughnut be consistent in every store,” said Richard Sides, VP of construction for Krispy Kreme. “If the humidity gets too high in the kitchen or dining area, the glaze starts to break down, and the doughnut begins to sweat.”

The key to achieving optimal humidity levels was to install a new system that would control humidity outside of the need for cooling. But this could get pricey.

“Selecting an inadequate dehumidification system affects product quality and can be very expensive to fix,” Sides explained. “Retrofitting HVAC systems with a dehumidification device is much more expensive than just installing a device from the beginning.”

The Right Choice

The architectural-engineering firm that works with Krispy Kreme recommended to Todd Buck, national account manager for Lennox in North Carolina, that he contact Krispy Kreme regarding using the Lennox L Series unit, featuring the Humiditrol® dehumidification system.

Buck was able to get in contact with the Hal Smith Restaurant Group, the Oklahoma franchisee of Krispy Kreme. The Krispy Kreme location in Tulsa, Okla., was chosen as the first location to use the Humiditrol unit. Buck said this product line has been successfully used in various applications, especially where food is the main line of business.

“Several grocery stores have adopted Humiditrol units to control humidity where continuous dehumidification prevents ice and condensation from forming on the glass of reach-in coolers and freezers,” said Buck.

He also explained that in the past, these grocery stores would control humidity by piping the hot gas off the compressors for the freezers and coolers back to a very large, single rooftop unit with a reheat coil.

“Since the Humiditrol uses its own compressors’ hot gas piped to its own staged reheat coil, they get humidity control without having to run all that pipe,” he said.

Buck explained that many establishments do not know the proper way to deal with excess humidity. “Anyplace where you see wet windows, they are overcooling to cut down humidity,” he said.

Obviously, cooler temperatures alone do not alleviate humidity levels altogether. In fact, Buck said that the new ASHRAE occupancy ventilation requirements have made the control of humidity and moisture more difficult. To fulfill these requirements, the HVAC equipment must introduce more outdoor air into the building. Much of this outdoor air can be humid, moist air, which Buck said has to be dealt with. Since the Humiditrol controls humidity independent of cooling demands, this can be accomplished.

With all of this in mind, Buck and representatives from Krispy Kreme said they believed that the Humiditrol would be a beneficial addition.

The Result

Three L Series units were installed at the Krispy Kreme in Tulsa; two of the units have the Humiditrol dehumidification system. Data loggers were used to measure the relative humidity (rh) inside and outside the new Tulsa store, as well as some existing stores in Atlanta and Greensboro, N.C., to find out just how much humidity had to be handled.

Data confirmed that most of the humidity was created by doughnut production. While the outside rh level at the existing Atlanta and Greensboro stores averaged 57 percent, the indoor level soared to an average of 71 percent. However, the Tulsa store with the dehumidification system had indoor rh levels averaging 53 percent.

Response to the units was overwhelming from representatives of Krispy Kreme, and not just because humidity levels appeared to be under control. The system was able to control operating costs. By taking hot gas from the compressor and supplying it to the staged reheat coil, the system was able to control humidity cost effectively.

The Hal Smith Restaurant Group was so pleased with the results that five more Krispy Kreme locations have been targeted to receive a Humiditrol.

Publication date: 08/11/2003