FER FOCUS: Walk-In’ The Talk

A walk-in refrigerator, or cooler, is a piece of equipment most of us take for granted—until it fails. Walk-ins, when specified and installed correctly, are designed to last a long, long time. So, when a walk-in goes down—usually in the middle of the night on a weekend—it’s cause for concern and maybe time for another look at the specifications.

The simplest walk-in to purchase and install is a prefabricated model. Available in a range of sizes starting at about 5 ft. by 5 ft. and increasing in 1-ft. increments, prefab walk-ins can be placed right on the slab of a new construction project before the building is framed or the walk-in can be disassembled at the factory and reassembled on site if the building walls are already up. For retrofits, rehabs and even new construction where the spaces aren’t standard, walk-in manufacturers custom-build units to fit.

Wall, floor and ceiling panels, which typically come in 4-ft. widths, are metal skins with insulating material sandwiched in between. Most manufacturers use foamed-in-place urethane rather than laminating the metal on polystyrene, a less expensive but also less energy-efficient method. Since new federal regulations were adopted several years ago, wall and ceiling panels must have a minimum R-factor—a thermal resistance value—of 25 or greater. Floor panels must have an R-value of 28 or more. (Walk-in freezers must have an R-value of 32 or greater.)

New U.S. Department of Energy requirements for energy efficiency go into effect for manufacturers in June 2017, but the minimum R-value requirements will not change. To see the new rules, go to 1.usa.gov/1pNKuEA.

Panels most often come in 4- or 5-in. thicknesses, but at least one maker offers one with 2-in.-thick panels, and several models have panels 6-in. thick. Even though all panels have to meet the R-value requirements, often the thicker the panel, the greater the insulating properties of the walk-in. If you have stores in the South where ambient kitchen and outdoor temps are higher year-round, you might want a thicker thermal barrier between the exterior and interior of the walk-in.

Size. Sizing a walk-in often is an afterthought. Once your consultant lays out the kitchen, whatever space is left over is allocated to the walk-in. But sizing is important. Too big, and you’re paying to cool empty space. Too small, and you can’t keep enough food on hand. Like the cooking line, the walk-in should be an integral part of planning and design. A number of factors go into sizing your walk-in. First is menu mix. How much fresh food vs. frozen do you plan on using?

The size of your operation and anticipated volume will help you gauge how much fresh product will rotate through the walk-in. Where your stores are located may have an impact on how often you receive deliveries. A restaurant in Northern Michigan may only get one or two deliveries a week from a food distributor. But stores in any major city can get daily deliveries.

Finally, other factors, such as whether your operation offers catering, banquet service or other foodservice in addition to your regular business, will affect walk-in size.

Refrigeration systems. Manufacturers do their best to balance refrigeration systems at the factory so you don’t have to worry about whether components are sized correctly. But you should keep in mind that an 8-ft.-by-10-ft. box in Florida requires about a 20% larger system than the same-size box in Vermont because of ambient temperatures. Likewise, a box in Ft. Collins, Colo., should have a larger compressor than one in San Diego, because of the difference in elevation.

Also note that you may have a choice of compressors on systems requiring more than 1 hp. Most smaller systems—up to about 1½ hp or so—use traditional hermetic or semi-hermetic compressors and hermetic compressors are available up to 3 hp. (Note components are accessible for replacement on semi-hermetic, but not on hermetic compressors.) Scroll compressors, which are more energy efficient, typically are found on larger boxes that need 2 hp or more. (Scroll compressors aren’t available in fractional horsepower sizes.) In recent years, costs of scroll and hermetic compressors have become more competitive.

Note that while oversizing a compressor sounds like a good idea, giving your walk-in power to spare, under normal conditions an oversized compressor ends up short-cycling instead of running continuously for longer periods of time, adding strain on the compressor and shortening its useful life. (An oversized compressor brings the box back to temperature more quickly and shuts off, but as soon as the temperature rises, it cycles again). A properly sized compressor runs longer to bring the box to temp. An oversized condenser coil, on the other hand, can help your walk-in handle excessive ambient temperatures—i.e., those summer heat waves that seem to occur with greater frequency. Most manufacturers also offer the option of water-cooled condensers (on a closed loop, of course) for large users.

System location. Locating the compressor and condenser remotely, such as on the roof, is more energy efficient than a self-contained system (see this month’s FER Report). Self-contained units typically are used in high-rise buildings where remote systems aren’t feasible or, by default, on outdoor walk-ins (a good solution when you don’t have space in the kitchen for a large enough walk-in). Manufacturers offer top-mount, side-mount and saddle-mount compressor/condenser configurations. Rack systems—compressors situated in parallel—are used in operations where walk-ins are unusually large or there are multiple walk-ins and other refrigerated equipment that can loop into one system, such as resort hotels, supermarkets or colleges/universities.

Construction and finishes. Insulated panels for walls, floors and ceilings typically are aluminum or galvanized steel, but you can spec a variety of materials for both inside and outside surfaces. Most manufacturers use a tongue-and-groove design for panels, and they connect using various forms of cam-and-hook interlocks.

Walls, both interior and exterior, typically are aluminum, but you also can spec painted zinc-prepped steel, painted aluminum, smooth anodized aluminum, embossed aluminum or stainless. For interior walls, remember that smooth surfaces are easier to clean than embossed, and dirt is more apparent on lighter surfaces than darker ones. If you store acidic foods in the walk-in, a painted surface is better than exposed metal. If your stores are near salt water, you will want to avoid aluminum and spec stainless walls, especially if the walk-in is located outside.

At a minimum, most building codes require panel metal thicknesses of .040 in. if aluminum, 26 ga. if embossed steel and 22 ga. if smooth galvanized or stainless.

Floors. Manufacturers offer a choice of floor panels, from standard strength that can handle about 600 lb. per sq. ft. to one with a plywood underlay that can handle about 1,200 lb. per sq. ft. to foamed-in-place panels reinforced with non-heat-conductive framing (wood or plastic) that transfer weight loads to the building floor underneath. Floor-panel materials usually are smooth aluminum for light duty floors, 1/8-in. aluminum diamond-tread plate for heavier duty floors and 16-ga. stainless for very heavy loads.

Ideally, walk-ins should be built on an insulated concrete slab, the floor covered with quarry tile and grout, with a thermal break—such as redwood—under the wall panels. This type of installation is required only for walk-in freezers, and floors of walk-in refrigerators located in basements don’t need to be insulated at all. Floorless walk-ins, though, should have some sort of thermal break, such as a vinyl seal between floor and wall panels. You should always check local building and health codes before you set specs. Some locales require smooth floors, for example, so you can’t use embossed or diamond-tread materials.

Doors. Besides the compressor, no part of a walk-in gets more use than the door. Many manufacturers have moved away from reinforcing doors with wood or steel braces, instead using Fiberglas-reinforced polymer, which is strong, lightweight and resists warping. Doors should be insulated in the same manner as a wall panel. Most come with two hinges (either right or left hand) and a door handle. Locks and security bars are optional. If your walk-in gets a lot of traffic in and out, consider adding a third hinge and spec’ing a heavy-duty, reinforced handle. Most consultants and service reps also recommend adding kick plates and/or wainscoting if employees roll carts in and out.

Don’t forget that code (Energy Independence and Security Act, H.R. 6, sec. 312) now requires plastic/vinyl strip curtains or air curtains and door closers on all walk-in doors. Most makers give you a range of options.

Controls. No longer boxes you plug in and forget, several makers offer walk-ins with a variety of controls. A digital thermometer is pretty standard on most models.

Defrost on demand. Older and/or less expensive walk-ins use a passive thermal-expansion-valve defrost cycle that runs the fan while the compressor shuts off to circulate walk-in air over the evaporator coil. The relatively warmer air (38˚F-41˚F) defrosts the coil, but can take 20-40 minutes or longer. On newer models, look for one of two types of active defrost cycles. The first is electric: You set a timer to run the defrost cycle at regular intervals, and an electric element heats the evaporator coil to thaw it. The other is an on-demand hot-gas cycle that injects hot refrigerant gas into the evaporator coil either through a bypass, or more commonly now, by reversing the refrigeration flow. Defrost cycles can be timed or activated by the temperature of the evaporator coil. The advantage of defrost control is energy savings because the defrost cycle runs only when truly needed and for about one-fourth of the time.

Door heaters. Many models now feature door heaters—electric heater wires that run around the door’s perimeter to evaporate condensation and ensure a tight door seal. Most have an on/off switch that lets you turn the heaters off when ambient temps are lower in winter. At least one manufacturer has a control for the door heater that lets you set the temperature at which it turns on as well as its operating temperature.

Alarm monitor. A walk-in that fails in the middle of the night can cost you tens of thousands of dollars in spoiled food. Temperature monitors trigger alarms when the walk-in temp rises above a certain set point. Controls let you set the activation temperature, the time delay before the alarm sounds once the activation temp has been reached and how the alarm is issued (audible, text message, phone call, etc.). Many models also incorporate a “door ajar” alarm that sounds after the walk-in door has been open for a set period of time.

Fans. In many older systems, fans often run continuously whether the compressor’s running or not. In newer systems, controllers can be set to turn off cooler fans when the temperature inside the box reaches a set point. Controllers also allow special settings, such as shutting down the entire system when the door is open during deliveries (which also is a time when the door-ajar alarm needs to be turned off).

Lights. To save energy, both in electricity and light bulb heat, all manufacturers at least have switched to fluorescent bulbs, either tubes or compact fluorescent lamps, and many now offer vapor-proof LEDs standard or as an option. Some manufacturers offer an optional light switch, and a few models also offer a light-management control that lets you set how long a light will stay on after the door has been opened. Some offer motion sensors to control lights.

The bottom line: Walk-ins aren’t plain boxes anymore. Make sure you get the specs right for your operations and their locations.

The Four Biggest Mistakes

Walk-in manufacturers and service reps we spoke with say operators usually get it right when they spec equipment. But they also agree there are four classic mistakes some make:

• Size. To max out available footprint, operators customize walk-ins and end up making them too big or creating unusable space. If another foot will give you an additional shelf—great. Otherwise, you’ve just created a bigger aisle and more cube to cool. Make sure the walk-in is high enough, too. Evaporator coils on one wall may render the top shelf there useless if the walk-in isn’t tall enough.

• Floors. Too often, floors aren’t spec’d to handle the loads going in and out of walk-ins or end up being the wrong type to meet local codes. While manufacturers are happy to sell you fabricated floor panels, they and others, such as professional installers, recommend getting away from fabricated floors if possible and insulating the building floor/slab.

• Value engineering. To save money, some operators and consultants value-engineer walk-ins, but be sure you don’t skimp on things like doors and finishes. Add the extra hinge and kick plates or wainscoting to doors so they last longer. And it’s inexpensive to paint the interior white, which makes the walk-in brighter so product is easier to find and dirt is easier to see.

• Alarms. For a few hundred bucks, you can add a temperature monitor and alarm to a walk-in. That’s cheap insurance to protect the thousands of dollars worth of food inside.

Walk-In Cooler Mfgs.

Advance Cooler Mfg. Corp.
advancedcooler.com

Airdyne Refrigeration & Air Conditioning/ARI Industries
airdyne.com

American Panel Corp.
americanpanel.com

Arctic Industries Inc.
arcticwalkins.com

Bally Refrigerated Boxes Inc.
ballyrefboxes.com

Chrysler & Koppin Co.
chryslerkoppin.com

Dade Engineering Corp.
daeco.net

Duracold Refrigeration Mfg.
duracold.com

Forma-Kool
formakool.com

Hussmann Corp.
hussmann.com

Imperial Brown
imperialmfg.com

International Cold Storage Co. Inc.
icsco.com

Kairak Inc./ITW FEG
kairak.com

Kold Pack Inc.
koldpack.com

Kolpak/Manitowoc
kolpak.com

Leader Refrigerator
leaderrefrigerator.com

Leer Inc.
leerinc.com

Master-Bilt Products/Standex
master-bilt.com

Nor-Lake Inc./Standex
norlake.com

Penn Refrigeration Service Corp.
pennrefrig.com

Polar King Int’l. Inc. (outdoor units)
polarking.com

Supreme Corp.
supremecorp.com

Tafco-TMP Co.
walkins.com

Thermalrite
thermalrite.com

Thermo-Kool/Mid-South Industries Inc.
thermokool.com

U.S. Cooler Co. Inc.
uscooler.com