Big Changes Come To Walk-Ins
New regulations and technology make today's walk-in refrigeration more efficient and environmentally friendly than ever.
By: Mike Sherer
Check out our related article "Walk-In Gallery"...
When's the last time you thought about your walk-ins? If your staff is trained to keep doors closed as much as possible and your design team did its homework, your walk-in coolers and freezers do what what's needed without much intervention.
Still, now's a good time to start thinking about your next walk-in purchase. Thanks to a confluence of eventsnew federal regulations that just took effect, and advances in technologytoday's walk-ins are more energy efficient than ever, and a lot greener. Manufacturers are adding plenty of new features and offering more bells and whistles than you've seen before.
The upshot: Walk-ins are sophisticated pieces of equipment that can help you save money. Here's how.
New Rules, New Cool
The big news is that new rulescoming out of California two years ago and now from the federal governmenthave have raised the bar walk-ins must meet in terms of energy efficiency. That's forcing makers to design and build them differently than they did even a year ago.
California's Title 20, pieces of which took effect between Jan. 1, 2006, and Jan. 1, 2008, set prescriptive design remedies for walk-ins that now include higher insulation values, automatic door closers or strip doors, electronically commutated motors (ECMs) for evaporator and condenser fans, and specific requirements regarding the use of glass in doors and anti-sweat heaters around door frames.
California didn't set any specific efficiency standards, since there's no standardized test method yet for walk-ins, but the state figured the prescriptive measures would likely save energy anyway. ECMs have been shown to use about 40% to 50% less energy than the old single-phase pole motors. And by increasing minimum R-values of insulation to R-28 for walk-in coolers and R-36 for freezers, the state pretty much assured users that new refrigeration equipment sold in California would be more efficient, too.
The federal regulations that went into effect last month as part of the Energy Independence and Security Act of 2007 mimic California's rules in almost every way except one. The federal standards for insulation aren't quite as high, with R-values of R-25 for coolers and R-32 for freezers.
Note that four other statesConnecticut, Maryland, Rhode Island and Oregonadopted the California Energy Commissions standards at the same time California did, so walk-ins and freezers sold in those states also are constructed with higher R-value insulation.
At the same time these higher standards are taking effect, refrigeration makers also have been confronted with a phase-out of R-22 refrigerant and other HCFCs. R-22 isn't used in refrigeration systems themselves, but it was used by some manufacturers to blow the polyurethane foam insulation into the doors, walls and ceilings of refrigeration equipment.
R134-a has become the standard in foodservice refrigeration, widely used due to its effectiveness, relatively low cost and green properties compared to older CFCs and HCFCs. As an HFC, R-134a is considered a non-ozone-depleting and energy-efficient refrigerant.
It is true, though, that while R-134a is better for the atmosphere, using it has caused a loss in R-value in insulation. Since the 1980sbefore the Montreal Protocol pushed countries to ban ozone-depleting gases like FreonR-value of insulating materials used in refrigeration panels has decreased by about 18%.
For the most part, manufacturers typically have increased the thickness of walls to get the same insulation value as before. Now some makers are switching to new polyurethane blends and foamed-in-place methods that minimize the decrease in R-values. A new HFC, 245fa, gives blown polyurethane a slightly higher R-value than R-134a, which represents the first time R-values have increased since '87, but as of now HFC-245fa costs more to use in manufacturing.
Building A Better Box
The double whammythe falling R-values of more environmentally friendly insulation and rising energy costs, along with a renewed focus on energy conservation to reduce greenhouse gas emissionshas manufacturers finding other ways to build more efficient boxes besides increasing the thickness of insulating panels.
Perhaps the biggest step manufacturers have taken is adding electronic control systems to walk-in coolers and freezers. Able to monitor the performance of various components in the equipment, these systems adjust to changing conditions and thus help save energy.
Older systems, for example, used thermal expansion valves to allow the refrigerator to cycle properly. These systems work using pressure and cycle automatically. Switching to electronic expansion valves allows the system to meter refrigerant based on the requirements of the whole system, resulting in more efficient cycles.
Defrost cycles, which used to be timed mechanically whether the cooler or freezer evaporator needed it, now operate only when the evaporator temperature requires it. Fewer defrost cycles mean more energy savings.
New reverse-cycle controls also improve the efficiency of the defrost cycle by essentially reversing the flow of the refrigerant through the lines, accomplishing much of the defrosting with hot gas.
Controllers also can be set to turn off cooler fans when the temperature inside the box reaches a set point. In many older systems, fans often run continuously whether the compressor's running or not. Controllers also allow special settings, such as shutting down the entire system when the door's open during deliveries.
Compressors with floating head pressure are another new technology being put to use on equipment in some areas of the country. Typically, makers set compressors at the factory and size them to operate at worst-case ambient temperatures. Head pressure might be set for 95°F plus 15°F, or 110°F, ambient temperature. When the ambient temperature outside is close to freezing, though, the compressor ends up working too hard. Compressors with floating head pressure lessen the work load when the outside temperature goes down.
Another neat trick some companies are adding to their boxes is a simple vent and additional fan blower. The systems bring in outside air when the ambient temperature goes below a set temperature, usually 35°F, to help cool the box interior. More cold ambient air means less work for the compressor. The company that retrofits walk-ins says the system only pays if you're in an area of the country with at least 2,000 hrs./year of temps below -35°F.
Two caveats though: Untempered dry winter air can evaporate moisture in food products unless they're tightly sealed, and outside air should be filtered if the vent is anywhere near a drive-through.
Much of the technology now being used in commercial foodservice walk-ins has trickled down from large-scale industrial operations like warehousing and supermarkets, including Scroll compressors and variable-speed ECMs. Expect to see more of this technology in the foodservice arena soon as it becomes more cost effective.
Prescription For Energy Savings
All the new prescriptive mandates for walk-ins are designed to improve energy efficiency. Manufacturers are taking many of them a step beyond what's required, though, and offering additional savings with standard or optional features. Some of these features include:
Automatic door closers or strip curtains now are required on walk-ins. Many refrigeration companies now make doors with spring-loaded hinges as standard equipment (though other types of door closers are permitted as well). Some offer hinged strip doors and air curtains as optional equipment in addition to the door-closing hinges. Some plan to spec future strip doors as standard equipment in combination with spring-loaded hinges.
Lights. Many manufacturers offer more energy-efficient fluorescent lights as an option to incandescent bulb fixtures, but more now make boxes with compact fluorescents as standard equipment. The new rules say interior lights must produce at least 40 or more lumens per watt. Expect to see more vapor-proof CFL fixtures offered as standard equipment.
Many boxes also are available with sensors that turn off lights when no one's in the walk-in to save even more energy. Now optional, more makers will be offering energy-saving light systems as standard soon, too.
Glass doors. Walk-in doors often are spec'd with a glass panel. Freezers now must have triple-pane glass that's either gas filled or comes with heat-reflective treatment. Similarly, cooler doors must have double-pane glass that's gas filled or comes with heat-reflective treatment. Cooler door glass also can be triple-paned, which some makers offer as an option.
Anti-sweat heaters around door and window frames also have to meet new efficiency standards. Heaters on freezers shouldn't draw more than 7.1W/sq. ft. of door opening. For coolers, heaters shouldn't draw more than 3.0W/sq. ft. Some makers offer an optional heater control that automatically turns off the door frame heater if the box goes above a set temp45°F, for examplewhen employees have the door open to put away deliveries.
Though not mandated, alarms also are offered on many models, usually as an option. Simple alarms, such as audio alarms that signal an open door or a walk-in temp that's too high sometimes, come as standard equipment on some models. More sophisticated options include temperature monitoring with automatic phone dialing and wireless capability.
Walk-In 101: A Review Of The Basics
Size. Sizing your walk-in depends on your anticipated volume and the amount of real estate you can surrender to cold storage. Walk-ins are available in sizes as small as about 5' per side up to gargantuan cold rooms, and can be ordered in practically any size in between in 1' increments. Most are available in two or three standard heights, but custom heights are available, too. Getting the size right is important, obviously, because cooling more or even less space than you need is inefficient.
Pre-fab or custom. Walk-ins are made by assembling interlocking insulated panels into walls, floor and ceiling. Most manufacturers make pre-fabricated units in standard sizes that you can drop into place. Pre-fabs are an option when you can spec the walk-in on new construction and put it in place during framing, before the walls have gone up. Weatherized units also can be dropped in place on a slab outdoors, right outside the kitchen, for example, if you're expanding and don't have interior space.
Most makers also have a line of walk-ins in standardized sizes that they can ship within five days. The difference between these and pre-fab models is that they're assembled on site, so you can fit them into an existing space.
In most cases, however, your stores, even new ones, have enough individual quirks to warrant a custom walk-in. Most makers build these units to your dimensions and specifications, assemble and test them in the factory, then disassemble them for shipment to the site.
Compressor sizing. In most cases, refrigeration systems are sized at the factory for the specific walk-in being built. Sizing will depend not only on the size of the walk-in but whether you plan to use it simply for cold storage or to cool products as well, and how much food goes in and out during the day.
Sizing also depends on geographic location. A walk-in in Florida will have to be sized about 20% larger on average than one in Maine for the same application due to the different loads on the compressors from ambient temperatures. Compressors in Seattle and Denver also will perform differently due to elevation; the higher the elevation the harder the compressor has to work. So, even if your store size is identical from one area to another, you should spec your walk-ins to reflect the store's location.
Self-contained or remote. Self-contained walk-ins are available but not recommended for most applications. They're typically used in high-rise buildings where there's no place to put the remote equipment. Putting the compressor and condenser outside costs more to install, but the savings in efficiency and maintenance over time will more than pay for the difference.
Construction and finishes. Modular interlocking insulated panels for the walls, floor and ceiling are typically constructed of aluminum or steel with a galvanized aluminum coating, but they come in a range of materials and finishes.
Walls typically are aluminum but you can also spec painted zinc-prepped steel, painted aluminum, smooth anodized aluminum, embossed aluminum or stainless steel. Floors may be embossed coated steel, stainless steel, or embossed or smooth aluminum. Smooth finishes are easier to clean. Embossed surfacesoften called stucco finishesare used on exteriors and on floors so they're less slippery. Some heavy-duty floors have an embossed diamond-tread pattern.
Floors typically are constructed to handle heavy loads but most makers offer reinforced floors if you plan to use hand trucks or heavier loads on large floor areas. Walk-in freezer floors must be insulated unless the building floor is insulated to the required R-value of 32 (or 36 in California, Connecticut, Maryland, Oregon and Rhode Island).
Shelving. Like walk-ins themselves, shelves can be constructed of a variety of materials, from ABS plastic to heavy-gauge stainless wire, depending on your needs and budget. Some are finished in epoxy paint to prevent corrosion, and newer shelving materials now sometimes include antimicrobials to help keep them more sanitary.
Standardized shelving systems are available with all walk-ins, and most makers offer customized shelving that will fit the dimensions of the walk-in you've specified. Custom shelves typically can be fabricated to desired lengths and heights in 1" increments.
Door handles and locks. Other than the compressor and fans, the only moving parts in a walk-in are the door and handle. Handles, hinges and door gaskets get the most use next to the compressor, so make sure they're heavy duty. Some makers offer a third hinge as an option on doors that get a real workout (standard on a few lines), and most have designed handles to take the abuse. Look for things like reinforced latches.
Often, you'll have the option of a keyed lock or a hole for a padlock hasp, some designed into the same handle. A few makers also offer an optional security bar.
Options. These include digital thermometers (usually built into the door frame), door alarms, temperature alarms, kick plates, interior and exterior floor ramps, foot treadles, and different types of lighting (e.g., fluorescent). Depending on the manufacturer, other options can include strap hinges, glass view ports or merchandising doors, independent fan and light switches, light monitoring systems, strip doors and more.
Maintaining your walk-in coolers and freezers is pretty simple. For starters, a clean walk-in is an efficient one. Your staffs likely are trained to keep both the interior and exterior clean and sanitary, but key components can sometimes be overlooked. Pay particular attention to:
Door gaskets. Keep clean and pliable. Replace when worn.
Hinges and door closers. Check regularly for proper opening.
Condenser and fan. Keep clean and free of grease so they can do a more effective job of transferring heat. Since most of you will use remote refrigeration systems, that will mean a trip up to the roof for someone on a regular basis.
Condenser and drain lines. Keep them clear and schedule checks of the seals where they enter the building.
Beyond checking these areas, it makes sense to schedule servicing every three months if your system is self-contained and every six months if it's remote. New walk-in control systems have self-diagnostics that may be able to warn you when components are working too hard or require service, which can reduce the need for service calls.
Temperature monitoring systems also can help predict when walk-ins need service. These systems, which can be wired or wireless, track temperature, humidity and whether or not the door is open on walk-ins. Most have options for sounding an audible alarm or sending e-mail, text message or voicemail alert when set points are out of spec.
By tracking alerts, these systems also can help you tell when equipment needs servicing. A walk-in that goes out of temperature specs during the night when no one's opening the door, for example, may be going through defrost cycles more than necessary, putting undue strain on the compressor.
Many manufacturers offer temperature monitors as optional equipment now, or you can purchase them from outside suppliers. For more on these systems see our story at www.fermag.com/sr/v12i12_sr_TempMonitoring.htm.
Check out our related article "Walk-In Gallery"...