FER FOCUS: Keepin’ It HOT!

So you’re looking for hot holding cabinets. You’re not alone. They’re hot items—pardon the pun—in many foodservice segments, from quick service to hotels and lots in between. Any time you’re producing batches faster than you’re serving them, you’re holding something somewhere.

But how do you know you need hot holding cabs, per se, as opposed to banquet carts, proofers or mobile transport carts? How are they different? Details vary from model to model, but in general, here are the quick rules of thumb: Banquet carts are equipped for plated foods. Proofers hold at lower temps, typically 80˚F-100˚F, and they control humidity for doughs. Mobile transport carts put more emphasis on transport. For rough handling up and down ramps, across thresholds and into and out of trucks, they’re more rugged, have bigger casters, etc. Those aren’t the only differences, but they’re a quick way to sort them.

Hot holding cabs are upright cabinets that hold bulk foods in various pan styles above 140˚F—usually in the 160˚F-200˚F range. They come in an array of sizes—one maker figures 90% of the market is full sized—6- or 7-ft. tall—with the remainder being smaller for special applications. Cabs come with or without casters and with or without insulation. Their heating systems may be up top or on the bottom. They may be lightweight or sturdier, riveted or welded. And then there’s humidification. You get the idea.

Holding: Where, And How Long?

Typically, a hot holding cabinet will last seven to 10 years or more in a busy commercial application, one maker estimates. In a school, where hours are shorter, the life expectancy is longer. So it’s worth thinking about getting it spec’d right.

To sort out the key spec considerations, we went to a half-dozen suppliers that really specialize in the category. Not surprisingly, they all said the details of the application are crucial to the spec process. Holding a dry item for a short time is nothing like holding something moist for a long period. Where and what are you holding, and for how long? You’ll need to think about how many hours a day the units will be running and how often the doors will open and close, impacting both temperature and moisture.

Let’s start with where and mobility. If your cab won’t be going anywhere, theoretically you won’t need casters. But most of the market—90% by one manufacturer’s estimate—gets them anyway, if only to ease moving the equipment around for cleaning underneath and behind. Basic casters typically are 5-in. in diameter. If you’re going to be rolling around a lot or if surfaces will be rough, you might go up to 6 or 8 in., but be aware extra height can affect handling and tippiness. No point in going all “off-road” on it. Well, unless you’re going off road. Get brakes, and check with your supplier about whether you’ll need particular wheel materials.

Basic construction is either aluminum or stainless. Entry level, basic cabinets are relatively light-duty—aluminum skins and frames with rivets. If you’re not moving the cabs around, and if the food holds well or holding times are short, these might be cost-effective choices. If you’re going to hold foods for any substantial length of time or you know you’ll be moving the cab frequently, you’ll want to do yourself a favor and look into upgrading to stainless and maybe welded construction for durability, rigidity and structural strength in general.

Keeping The Heat In

For infrequent or brief use (maybe 10 or 15 minutes depending on how sensitive your food item is), insulation might not be necessary. But if you’re holding foods for longer than brief periods, or holding batches often throughout the day, you’ll need to consider insulation. It’s tempting to shave a few dollars here and there, but insulation probably is not a good place to find savings. Efficiency data from Pacific Gas & Electric’s Food Service Technology Center a few years back indicated typical payback on insulated vs. non-insulated is about two years, depending on electric rates. After that, the savings all go to the bottom line. Manufacturers report that more and more of the market goes with insulation not only for its energy-saving advantages, but also for cooler cab surfaces, less heat gain in the workspace and improved employee safety. Insulation also involves an inside layer of aluminum or stainless, so cab rigidity benefits as well.

“In general, insulated cabs cost twice as much as non-insulated,” one maker notes, particularly when comparing lower-end models. “There’s a polymer-panel insulation out there that cuts the differential to about a third, but generally about double.” Most insulation is fiberglass-type matting. One maker we talked with does a foamed-in-place process usually only found in refrigeration.

Another payback on insulation can be reduced component failure. “When a cabinet fails, it is an electronic component,” another factory spokesperson says. “A noninsulated cabinet cycles more, maybe 12 times an hour instead of six, to maintain temperature. That puts more strain on heating elements and thermostats. Thermostats maybe last two years in an uninsulated cab, or maybe four years or more in an insulated one.” He notes basic thermostats can run $300 or more, not counting service charges.

Heating, Air And Moisture

As for heating, you’ll find your choice of top- and bottom-mount systems with elements and controls located near each other. Proponents of top and bottom each have their reasons. Top locations might offer easier access, and components stay cleaner because nothing is dripping on them. Bottom mounts, which are less expensive and still make up the majority of the market, historically benefited from the fact that heat rises.

So top or bottom mount was a big consideration, especially back when most cabinets used radiant heat. Today, though, virtually all of the market uses a fan for convection; rising hot air eventually gets circulated downward. The fan improves even heating from top to bottom, which is good, but you need to keep in mind how much airflow your product can take and for how long before it starts drying out. Talk with your equipment suppliers about your specific food applications. And if you need to unplug the cab for mobile duty, think about this: One maker notes unplugging means the fan shuts down, so the heat inside will rise to the top. The longer the cabinet is unplugged, the more pronounced the effect. Consult with suppliers about your specific needs.

So how do you direct airflow? Duct systems add cost, but they work better than unducted air blowing willy-nilly into a couple of pans that block the airflow from other pans. In a duct system, a top-mount fan might drive air down a “chimney” or duct, where it emerges at the bottom and then rises naturally. Or some systems might be more elaborate with specifically directed, cross-shelf ducting. Either way, the goal is to get airflow contacting the pans and/or food surfaces. Not a harsh wind—just a gentle, low-velocity movement.

Which brings us to food questions. Will your food pans be covered or uncovered? Covered will retain moisture, which is a good thing. Uncovered foods will lose moisture to evaporation. The longer they’re in holding and the more airflow or heat is involved, the more moisture can evaporate.

Active Or Passive

So, what about humidity? If you’re holding uncovered moist foods for a long time, you definitely need humidification. And probably most people need humidity systems on a sliding scale from high tech to basic.

On the high end, you have active humidity controls. The most sophisticated actually measure relative humidity and can maintain specific levels depending on the requirements of the food you’re holding. Other systems use elements in a water reservoir to generate humidity. Some models use a simple pan of water for passive evaporation.

“A lot of cabinets might have no element but a pan of water,” one maker says. “That creates some passive humidification. But, really, you need an element in or under the pan to generate moisture. Remember, the hotter the air is, the more moisture it will hold.” 

It’s worth noting here that you’re not humidifying to add moisture to the food, but to put enough moisture into the air to slow down the evaporation process. “What kind of food product are you holding? If it’s mostly proteins, uncovered, then you want some controlled humidity. Otherwise, just use plastic wrap or foil,” he says.

One parting thought on humidified cabs: Some of them cannot operate in a dry mode, so think about that if you’ll sometimes need dry holding. 

Rack Slides And Hardware

Once you’ve nailed down all of those big considerations, keep an eye on the small details too. First, rack slides. Getting slides to fit your pans and vice versa has always been a hassle, and it still can be today. You can choose racks to fit sheet pans, hotel pans or Gastronorms. But a lot of manufacturers now are offering adjustable, “universal” slide systems that are easier to change or adjust in the field.

Choosing doors? Most makers offer some or all of the following: solid doors, clear doors, Dutch doors and pass-throughs. Glass doors are nice for looking inside, but consider that single-pane doors can lose heat, so go for double-pane doors if that is an issue. If you’re moving the cab, solid doors will be sturdier. Handles mostly are pull style and magnetic. For mobile cabs, consider flush-mount handles to avoid catching things on the move. Doors should be field reversible. The electrical cord location and lengths need to reach your outlets: Think about where your power sources will be. And if the cabinet will be moved around, think about how the cord will be stored out of harm’s way in transit. Look for right-angle plugs to fit into tight spaces and avoid damage to the plug.

Another note for mobile cabs: 20A draws are popular now for quicker heat-up, but some locations only have 15A. You don’t want to haul a cabinet somewhere and find out you can’t use it, so double check.