How to Spec Walk-In Coolers
The premise of a walk-in cooler is obvious: it’s a cold box for storing foods and beverages. But there’s more technology in and on the box than you might think—and manufacturers have made recent advancements. Federal regulations now require newer environmentally-friendly (yet slightly less efficient) refrigerants; however, manufacturers have simultaneously reduced the electrical load needed for cold storage and thus minimized its carbon footprint. At least one supplier has further improved the efficiency and lengthened the useful life of its cold boxes with new construction methods that keep the compartment airtight and watertight even at the vulnerable points in the corner joints and around the door frame. Newer units feature door status alarms, doorframe heater wire shutoff systems, automatic temperature data recording for HACCP, even remote alarms and remote control through USB ports.
Who Needs a Walk-in and Why
There’s no simple formula to determine whether a restaurant’s volume, hours of operation, menu and food preparation system would merit the addition of a walk-in cold box. If meat, fish and produce arrive daily, reach-in refrigerators may provide adequate storage. But if you’re finding that staff are having to replenish supplies constantly, you may want to consider a walk-in cooler for backup. (You can even add a reach-in door to the walk-in.)
Several makers note that today’s greater emphasis on fresh fare has increased overall demand for walk-in coolers—and, correspondingly, reduced demand for walk-in freezers.
A reach-in cooler should be the first choice for cold storage of items that will be accessed many times an hour. If you have products that are going to be stored for days or if you’re storing in bulk, then you will want to use a walk-in cooler, says one manufacturer. “The walk-in is your bank for food storage,” says a sales and marketing vice president. (If you’re storing items for months, you’ll need a walk-in freezer.)
Why not just add more reach-in refrigerators? “If you keep adding reach-ins, you’re adding more condensing units and lots of electrical service to a job site,” explains one supplier’s director of operations. By going to a walk-in cooler, you’re cutting down substantially on utility costs—particularly since walk-ins also are much better insulated than reach-ins.
Some operators may actually require more than one walk-in cooler if they’re storing a lot of beer or wine. While 35°F-38°F is a good temperature for storing multiple items together such as produce, meat, fish and beverages, a specialized beer cooler will hold the beverage at a lower temperature and a wine cooler too will provide less chill (about 50°F). If space is a concern, it’s possible to site the box and condenser elsewhere in the building, or even outdoors. It’s even possible to cut a door in an exterior wall to access the unit, although that would add to the cost.
How Big and How Powerful
When specifying a walk-in cooler, figure size from the inside out—that is, begin with the space needed to store the specific items required for your operation. If crews will bring carts inside the walk-in, for example, they’ll require approximately 40 in. of aisle clearance. Taking that into account, decide the width, depth and height of shelves needed. From that, you can derive the interior volume and dimensions of the box. Then you can figure the exterior size, given the type of construction and the thickness of the insulation used (see “Understanding Insulation” at right). The smallest, simplest and least expensive walk-ins are off the-shelf units in sizes such as 6-ft.W x 6-ft.D or 8-ft.W x 8-ft.D, with the compressor typically mounted on top. (Remember to take these units’ typical 7 1/2-ft. height into consideration when figuring what model will fit the space.) These units are often available for order online and don’t require long lead times for manufacturing and installation.
However, many manufacturers offer custom sizes, building both the box and the refrigeration system. They work closely with dealers and end-users to meet the project’s specific needs.
“One mistake that buyers make is settling for standard panel sizes instead of getting the maximum storage space possible when the manufacturer can custom design the walk-in,” says a vice president of sales and marketing. “We can manufacture high-density perimeter wall panels, which allows us to manufacture in 1-in. panel increments. So, the customer can draw the line where they want the walk-in, and we build it to fi t: height, width, exact size of shelving needed, even the door location, which can be as close as 6 in. from the corner.”
The horsepower and Btu load of the refrigeration system matter as much as the size of the box itself. There are many factors to consider in refrigeration sizing, not all of them obvious. In sizing refrigeration, always consider the humidity in the room where the walk-in cooler will be placed. Air flow also is a factor, especially if the refrigeration system is sitting on top of the walk-in. Without proper air flow, the compressor will not function properly.
“Usage is critical,” says a product manager. “We assume the average user is going to open the walk-in door six to eight times an hour, and we size the refrigeration system based on that factor. We try to put a cushion into the design to accommodate whatever the customer does.”
Considering the Extras
"You may not need all the 'bells and whistles,' but some options can prolong the life of the walk-in while making your life a lot easier," one manufacturer's product specialist points out.
One company's standard control system for its walk-ins comprises a light control, audiovisual temperature alarm, temperature data monitoring, onscreen diagnostics and a cyclic heater and monitoring system for each door. Its more advanced controller option adds a time and date monitor to help document any incidents, a secure digital memory card interface and a PC connection kit, among other enhancements.
"In the past few years, more buyers are recognizing that if they buy the newer electronic controls that are optional for refrigeration systems, they pay for themselves rather quickly," notes a product manager.
For example, one supplier offers a controller that you can program for demand defrosting; it can reportedly save 30% on energy consumption per year.
By mapping out the ideal interior and exterior dimensions, right-sizing the refrigeration system and adding on important accessories, you're sure to build a walk-in cooler that best supports your operation.
According to the U.S. Department of Energy, an insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value. The higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation, its thickness and its density. Walk-in coolers have higher R-value insulation than reach-ins (the DOE requires a minimum R-25 insulation for walk-in coolers, versus the R-16 that’s typical for reach-in refrigerators).
Two types of insulating materials are primarily used for walk-in coolers at foodservice operations. Extruded polystyrene has an R-value of 5 per in. Thickness. It’s typically produced as a board stock that’s cut to panel size, laminated to interior and exterior metal panels and glued to the cooler’s frame, with a less dense foam filling in the gaps at the corners.
Foamed-in-place closed-cell polyurethane insulation, widely used in custom walk-ins, has an R-value of 7.2 per in. Thickness. Polyurethane permanently adheres to structural panels that have already been bolted in place, adding strength and reliability. In addition, the foam’s density means superior moisture resistance. Because the cooler’s walls can be thinner with foamed-in-place polyurethane, inside storage space is maximized in relation to the size of the box. And because the compressor and condenser don’t have to work as hard to keep food cool, better-insulated walk-ins will likely have a longer useful life.
Manufacturers give competing arguments as to which type of insulation makes most sense. Ask the maker of the model you’re considering to show the facts about the insulation and ask about the manufacturing process. Ask for the R-value and warranty information.
Cold Holding is Not Blast Chilling
Specifications for walk-in coolers are based on the premise that food and drink are coming in cold, or at least at room temperature. One of the issues that suppliers see most frequently is operators batch-cooking menu items and placing large amounts of hot food into the cooler, straining its refrigeration system and raising the temperature of other items.
You might be able to reduce the strain on the cooler (and the food safety danger of too-slow chilling) by putting hot food into multiple smaller containers and pre-cooling it in an ice bath before loading it in the walk-in. But that’s a makeshift solution.
If you’re cooking product in-store, a blast chiller is the better answer. Certain remote-refrigeration blast chillers can be placed inside walk-in coolers, so employees can unload the chilled food for storage without putting it through a room-temperature environment on the way from cooling to holding.