Gas and electric combi ovens cook using hot air and/or steam and can be versatile workhorses in commercial kitchens.

Combi Ovens: An Overview

Combi ovens combine various technologies to cook food. These versatile units can serve as a convection oven, convection oven with moisture, steamer, low-temperature steamer/sous vide cooker, combination oven with heat and steam or rethermalizer.

"There can sometimes be a disconnect between who is purchasing the combi oven and who is using it, so we've seen operators not know the full capabilities of this equipment," says L. Daniel Bendall, principal at FoodStrategy Inc., a foodservice consulting firm based in Rockville, Md. "This is a very expensive convection oven, if an operator is not taking advantage of the steam features or combi modes. Training at the user level is crucial."

Foodservice operators can choose from full- and half-size combi ovens in addition to countertop models. Sizes range from units that accommodate 4 half-size steam pans up to roll-in units that allow for a capacity of 40 full-size steam pans. Larger units can also accommodate from 6 to 20 full-size sheet pans. Ovens utilize either basic manual controls or digitally programmable features.

While combi ovens feature stainless steel construction, gauge and type of stainless vary by manufacturer. Most combi ovens utilize corrosion-resistant stainless steel exterior panels. Cooking chambers generally feature 304 stainless steel, which helps them weather potential water quality issues based on cooking technology that integrates steam with convection heat.

The ovens vary by whether they use a boiler to produce steam. If a foodservice operator plans to use a combi oven more like a steamer, meaning the plan calls for regular full load steaming, a boiler-based unit would be the best option.

Combis also provide convection modes, using dry convective heat to roast, bake and finish off food.

What makes these units unique is the combination mode, which utilizes both steam and convection heat. The benefits of cooking in a moist environment include retention of natural nutrients and increased food yield. Additionally, the use of steam with convection can reduce cooking times by up to 60 percent compared to traditional methods.

These ovens also can be used to rethermalize as part of a cook/chill operation or for pre-cooked convenience items. This mode is commonly utilized in banquet operations, when food needs to be cooked in advance.

"When people use a combi oven and see what it can do, virtually everyone thinks it's a great multipurpose piece of equipment," says Bendall.

How to Know When to Replace Combi Ovens

Like other pieces of cooking equipment, combi ovens have an expected asset life cycle ranging from 7 to 10 years, if operated and maintained properly. Here are four signs it might be time to replace a combi oven.

Deteriorating condition: When an older unit starts showing its age, whether with dents, rust or other visible signs of deterioration, it may be time for a replacement. Also, utilizing unfiltered water will cause lime buildup and can significantly shorten the oven's service life.

Reduced cooking efficiency: If it becomes costly to operate the combi oven because the unit works harder to maintain proper cooking temperatures, a replacement may be necessary. Combi oven technology continues to evolve, incorporating new cooking features, greater efficiency, smaller footprints, ventless options and enhanced control technology.

Increasing maintenance costs: When the service costs begin to escalate, operators should weigh the cost of running the combi oven versus purchasing a new, more energy-efficient model. Plus, parts may become obsolete, which will necessitate replacement.

Compromising safety: Safety of the operator should always be front of mind so if the equipment is deemed unsafe to operate for any reason, the combi oven should be retired.

Combi Oven Applications

Commercial kitchens from all foodservice industry segments use combi ovens. Here are several examples of how foodservice operators use combi ovens to support their menus.

Foodservice operators can incorporate combi ovens into cooking lines as a finishing oven, utilized for high-volume production and cook/chill and also for rethermalizing.

Combi oven cooking techniques include poaching, blanching, steaming, sous vide, rethermalization, roasting, broiling, oven frying, baking and braising. Some combi ovens feature an integrated smoking capability to produce both hot- and cold-smoked foods.

In recent years, combi oven technology has become a staple in retail foodservice, with more units replacing traditional rotisserie ovens due to faster production speed, enhanced food quality and extended shelf life benefits.

The technology has also become more common in the fast-casual and QSR segments as a tool that allows consolidation of the kitchen package, streamlining of production through menu versatility, speed of production to service and reduction of overall space and capital investment.

Maintaining Combi Ovens

Most combi ovens include automated cleaning systems, although this feature can differ significantly, depending on the unit's design. Here are six tips to help ensure a combi oven continues to run effectively and efficiently.

Ideally, combi ovens should be rinsed down daily and thoroughly cleaned once a week.
"Regular preventative maintenance is essential on this equipment," Bendall says. "It includes many electronics, so it's important to follow manufacturer recommendations."

Automated cleaning systems help reduce labor and allow the operator to manage costs in terms of cleaning chemical usage. Combi ovens with this feature provide a variety of options and cleaning levels. These range from a 20-minute quick rinse to heavy-duty cleaning, which could be a three-hour process in some ovens. The benefit of this is that the operator can select the level of cleaning needed.

Below is basic cleaning and maintenance information, but manufacturer's recommendations also should be followed.

  • Combi ovens can be set to automatically clean on a set schedule as well as to delime when necessary. If the oven doesn't have the controls to program cleaning or deliming on a schedule, then it's usually accomplished with the touch of a button.
  • Cleaning chemicals used with these units vary significantly. Cleaning tablets are commonly utilized with combi ovens today. The tablets dissolve in water and at certain temperatures resulting in a contained slurry, which is circulated through the oven, similar to a dishwasher.
  • Some models utilize liquid concentrate and sanitizing chemicals for cleaning, which can be remotely pumped to the oven.
  • Most ovens also have a means of decalcifying and preventing limescale buildup in the boiler or steam generator. In the case of boilerless technologies, the oven cavity must be treated.
  • Operators should only use cleaning chemicals recommended by the equipment manufacturer, as some agents can be aggressive and damage the oven interior as well as components. This can potentially result in voiding the original manufacturer's warranty.
  • "Many combi ovens have self-cleaning features, like a spray hose on the side, since there can be taste or odor transfers from product to product if the cavity is not kept clean," Bendall says.

Spec Check: Combi Ovens

One of the benefits of combi oven technology is that it can replace other pieces of equipment, saving money and kitchen space.

Menu needs: Foodservice operators need to determine the type of food being prepared in the oven. If a menu item requires steam, a convection oven and even a traditional kettle, combi oven technology would be a good fit.

Size and capacity: When changing from a traditional oven to a combi, many make the mistake of specifying on a cavity for cavity basis. A single combi oven can often out-produce a convection oven. This not only saves space but can result in equipment cost savings. "We caution people not to oversize a combi oven," Bendall says. "Smaller ovens that accommodate six or 10 pans are fine for most restaurants."

Location: Physical space is a consideration both for placement as well as access to the equipment. These ovens require exhaust hoods, so it's important to ensure room is available. Clearance for the unit's doors is another factor to keep in mind.

Utility access: Combi ovens require access to a water supply, drainage, electricity and possibly gas, so assessing utility availability and connections is key.

Cleaning: Foodservice operators short on time should consider self-cleaning combi ovens. Also, operators need to determine the type of cleaning chemicals required, as some ovens will need specific supplies that can add to the long-term cost of owning the unit.

Energy Efficiency and Combi Ovens

Combi ovens offer a variety of energy-efficient options.

The Energy Star Commercial Oven Version 2.1 Specification was updated on September 30, 2013, and took effect on January 1, 2014. It states that gas combi ovens have an idle rate less than or equal to 6,511 Btus per hour in steam mode, with cooking energy efficiency greater than or equal to 41 percent. In convection mode, gas ovens must have an idle rate less than or equal to 5,425 Btus per hour, with cooking energy efficiency greater than or equal to 56 percent. For electric combis, the steam mode idle rate should be less than or equal to 6400 kW, with a cooking energy efficiency greater than or equal to 55 percent. In the convection mode, electric combis are required to have an idle rate less than or equal to .4989 kW and a cooking energy efficiency greater than or equal to 76 percent.

Efficiency options vary, depending on manufacturer design. Utility consumption is dependent on whether units are boiler/steam generator or boilerless, with the latter typically requiring lower water consumption.

One manufacturer's model captures heat and humidity in the oven cavity, rather than allowing it to escape through the oven drain. This design enhances the unit's energy efficiency.

Units with multiple power modes also have an impact on oven efficiency based on operating mode.