Currently, the two primary types of walk-in refrigerators and freezers are prefabricated and built-in. The prefabricated walk-in is usually con- structed from a series of 4-inch (10-centimeter)-thick modular panels. Each panel is made with urethane insulation material that is foamed into place between two sheets of metal. The kinds of metal that can be speci- fied for prefabricated walk-ins include:
❏ Galvanized steel
❏ Painted galvanized steel ❏ Aluminum (embossed or plain) ❏ Painted aluminum
❏ Stainless steel
Walk-ins are often specified with several different finishes, such as white painted aluminum for the interior walls and ceiling, stainless steel on the exposed exterior walls, a galvanized steel on the unexposed interior walls, and galvanized steel on the interior floor so that quarry tile can be installed over it.
These panels are attached to each other (with a variety of latches and bolts) to form the outer walls, ceiling, partitions, and floor (optional) of the refrigerator. They can be purchased in many combinations of heights, lengths, and widths. A walk-in cooler is illustrated in Figure 7.3.
The specification of a prefabricated walk-in using the manufacturer’s standard modular panels produces a refrigerator that is “nominal” in size. Each manufacturer determines the nominal widths, lengths, and heights of standard panels. A manufacturer’s walk-in that is described as 8 feet by 12 feet (2.44 m by 3.66 m) may actually be 7 feet 6 inches by 11 feet 4 inches (2.32 m by 3.45 m) when built using standard panels of nomi- nal size. Custom or full-size walk-in refrigerators are available and can be purchased, at an additional cost, in almost any size. The primary dif- ference between nominal-size and full-size walk-ins is cost. Nominal-size units, because they use standard panels, are less expensive to manufacture than units requiring custom panel sizing. Knowing the difference between standard (nominal) and full-size walk-ins is critical when specifying these units.
Figure 7.3. Walk-in Refrigeration. Courtesy
of THERMO-KOOL/Mid-South Industries, Inc.
Prefabricated walk-ins can be installed indoors using a number of dif- ferent flooring systems, each with advantages and disadvantages:
Manufacturer’s floor recessed into a pit. A pit about 4 inches (10 cm) deep and slightly longer and wider than the walk-in is built into the concrete subfloor of the building. The walk-in’s floor panels are set into the pit. Then quarry tile (or a similar flooring system) is run continuously from the kitchen into the walk-in. The primary advantage of this approach is that carts and racks can be taken in and out of the walk-in across a level surface. This approach is ideal in new construction where the concrete subfloor can be poured with a pit at little additional expense. The disadvantage of this approach is that it may be impractical in a renovation, where cutting a pit in the existing floor is prohibitively expensive.
Manufacturer’s floor with ramps. A ramp into the walk-in is neces- sary where the floor cannot be recessed. Ramps can be built either in the interior or the exterior of the walk-in. Interior ramps are fur- nished by the walk-in manufacturer. Exterior ramps often are built by the contractors who pour the floor and lay the tile. The disadvantage of this approach is that ramps can be steep enough to cause spillage as food items are carted up and down. The manufacturer’s floor should be specified to be able to withstand the maximum point load of the object, cart, or shelving to be stored in the walk-in.
Installations without manufacturer’s floor panels. Prefabricated walk-ins can be installed without the manufacturer’s floor panels. In this approach the walls are anchored to the building floor on screeds that seal and support the structure. This approach provides a level passage from the kitchen into the walk-in. However, this approach requires insulating the floor under freezers to prevent the concrete from cracking due to temperature differences.
For many years, the working surfaces of walk-in coolers were made of galvanized steel. Despite the galvanizing treatment, steel floors proved to be vulnerable to pitting and rusting due to the moist conditions in coolers. The floors often wore out long before the rest of the unit, cre- ating unsanitary conditions. The National Sanitation Foundation (NSF) now requires walk-in floors to meet substantially tougher standards for endurance. Stainless steel is an acceptable flooring material, as is alu- minum tread plate provided that it is fully coved and integrated into the floor system. Galvanized steel can still be used in a walk-in cooler, but only if it is covered with another material that is acceptable as a working surface. Quarry tile is one such material.
A built-in refrigerator or freezer, which is more expensive than a pre- fab, is constructed of insulating foam walls, floors, and ceiling that are protected with structural glazed tile walls, quarry tile floors, and alu- minum or stainless-steel ceilings. Large built-in refrigerators may also be constructed of fiberglass panels laid over the insulation. The built-in refrigerator has the advantage of lasting many years under conditions of heavy use but the disadvantage of being more expensive and more difficult to enlarge or move.
Walk-in refrigerators and freezers are usually specified with either self-contained (top- or side-mounted) or remote refrigeration systems. The self-contained units are usually hidden on top of the walk-ins by closure panels, but sufficient air space must be available to prevent the air-cooling units from building up heat in the space above the walk-in. If the large air mass in the space above the false ceiling is insufficient for removing the heat of the compressor, additional ventilation will be necessary. Remote refrigeration systems can be located some distance away either inside or outside the building, but the farther the distance, the greater the heat (effi- ciency) loss. Remote refrigeration has the advantage of keeping noise and heat away from the food production area. Refrigeration systems can be ei- ther air-cooled or water-cooled, depending on environmental conditions and utility availability. Heat recovery equipment is an important acces- sory to refrigeration systems because of high energy costs and can be effec- tive for preheating water or heating space in the building. Preengineered refrigeration systems with multiple compressors are often specified for large food operations, providing greater energy efficiency and longer com- pressor life.
Common accessories and features that may be added to the walk-in specifications are:
❏ Outdoor, protected refrigeration systems
❏ Freezer alarm system that activates when the temperature reaches 15◦F (−9.4◦C)
❏ Extra interior vaporproof lights
❏ Roof caps for walk-ins located outdoors
❏ Wall protectors to prevent damage from carts (interior or exterior) ❏ Ramps for walk-ins not level with the floor
❏ Locks for doors ❏ Windows for doors
❏ Closure panels and trim strips for improving the outside appearance ❏ Thermoplastic strip curtains to reduce loss of cold air when door
is open
❏ Foot treadle openers for doors
❏ Air vent to relieve pressure when doors are opened or closed ❏ Glass access doors for placing foods in the walk-in without the
necessity of walking in
REACH-IN REFRIGERATORS AND FREEZERS
The word “refrigeration” refers to mechanically cooled refrigerators and freezers, and “refrigerator” means a refrigeration unit that maintains a temperature of 36◦F (2.2◦C) to 40◦F (4.4◦C). The most frequently
used refrigerators in all types and sizes of food facilities are the reach- ins. The versatility, reasonable cost, and storage efficiency explain why this kind of refrigeration is popular. Figure 7.4 illustrates a reach-in refrigerator.
Reach-in refrigerators can be purchased with one, two, or three com- partments and are available with many different options and accessories. In selecting this type of equipment, consider these questions:
❏ Will space and budget permit the installation of one, two, or three compartments?
❏ Will the refrigerator be used for general storage or for special prod- ucts that would fit better on interior tray slides?
❏ Should the refrigerator be adapted for roll-in carts, which eliminate all interior shelving?
❏ What capacities of storage are needed for reach-in refrigerators and freezers in the food production area?
❏ Is this refrigeration the primary cold storage capacity for the food facility, or is the refrigeration being used to augment walk-in re- frigerators and freezers?
❏ What special features would the owner like to have specified for this refrigeration?
Typical specifications might include:
❏ Automatic condensate evaporator, which eliminates the need for a floor drain
❏ Adjustable shelving or tray slides to accommodate trays that are standard in the foodservice industry, such as 18-by-26-inch sheet pans, 12-by-20-inch steam table pans, or 530-by-325 mm gas- tronorm, a well-known pan size in Europe.
❏ Cam lift on spring-loaded hinges that cause the doors to close automatically
❏ Stainless-steel interior and exterior, or a combination of anodized aluminum and stainless steel, or all anodized aluminum
❏ Exterior thermometer ❏ Interior lighting
❏ Full-size door or half doors ❏ Doors with glass windows
❏ Pass-through (doors on both sides)
In summary, there are many options available to the food facilities planner in choosing refrigeration for a food operation. An excellent source of information is an equipment catalog from one of the leading refrigera- tion manufacturers. These can be seen in the offices of the food facilities consultant or at a dealer’s showroom or can be obtained directly from the manufacturer.