Commercial Cooking Equipment
Whether it’s electric or gas, the type of cooking equipment you use determines your productivity, efficiency and yield. Electric cooking is the smart choice for today’s energy efficient kitchen. Explore the advantages of electric cooking equipment and learn how to maximize your energy dollars and grow your business. Let Georgia Power show you how electric cooking technologies will help you enhance profitability, reduce kitchen heat, improve yields and increase productivity.
In general, a building’s ventilation system must bring in enough fresh air for occupant comfort, while also controlling indoor temperature, humidity, and air quality to ensure personnel and building safety—all at a reasonable energy cost. Kitchen ventilation systems have the added burden of removing the grease vapors, odors, moisture, smoke and heat generated by cooking. They also play an essential role in fire protection.
The design of kitchen and other food service ventilation systems requires a professional, and it should not be attempted by unqualified persons using the guidelines and general comments offered here. The intent of this information is only to familiarize you with ventilation design considerations and typical equipment solutions.
The creation of grease vapors, odors, moisture, products of combustion, and smoke is generally focused in specific kitchen areas and varies based on the equipment used. The common solution is to vent, capture, and possibly eliminate contaminants through carefully designed hoods with adequate venting flow rates and fresh air makeup. Simply oversizing the vent system is not a proper approach and can be very costly in energy bills. A successful and economical design requires careful consideration of cooking equipment selections, cooking equipment arrangement and coordination in the kitchen, and appropriate vent-hood design.
Heating, ventilating, and air conditioning (HVAC) costs are significant in most food service businesses. Furthermore, failure of the HVAC system in the kitchen is reflected in worker productivity and possibly in worker turnover. HVAC system design requirements in the dining areas are simpler, but must consider both customer comfort and economical building operation.
In addition, the HVAC design must consider the way space is operated and maintained. If the space is a commercial kitchen in a much larger building, like a hospital cafeteria, energy systems are probably maintained by a professional staff. In these cases, system options can be reasonably sophisticated. On the other hand, if a food service establishment is an isolated small building, like a fast food restaurant, the staff are probably only going to operate systems by pressing simple start and stop buttons, so the HVAC systems should not be difficult to maintain or operate. These are probably not situations where more elaborate and complicated systems should be considered.
Ventilation Components – Type I, Type II
Commercial kitchen heating, ventilating, and air conditioning systems are similar to standard building designs except for make-up air systems and hoods. Make-up air systems include wall registers, ceiling diffusers, and slotted ceiling panels. Kitchen hoods are designed for specific cooking situations and are divided into two broad categories: Type I and Type II.
Type I hoods are used for the collection and removal of grease and smoke. They always include filters or baffles for grease removal and are normally required over fryers, ranges, griddles, broilers, ovens, and steam jacketed kettles.
Type II hoods are general-duty hoods for the collection and removal of steam and water vapors, heat, and odors where grease is not present. Therefore, these units may not have grease filters or baffles. They are typically used over dishwashers, steam tables, and similar equipment. However, they may also be specified for use over other equipment when allowed by local codes and authorities. Always check with a design professional for these rulings.
Ventilation Maintenance Issues
HVAC systems are a significant part of energy costs for most food service operations. The single most cost effective way to reduce these costs is to ensure that energy systems are operating properly. However, building systems are often unintentionally defeated when occupants complain about being hot or cold. For example, complaints about being cold during the hottest days of the year may cause adjustments to be made in setpoints for the system. When the weather later changes, the setpoints are probably not reset to a more economical setting. Furthermore, checking for a system problem that caused the discomfort in the first place is rarely done.
When breakdowns occur, there is a natural tendency to quickly patch the system back into operation instead of looking at improper system operation as part of the cause for the system failure. For example, an important routine maintenance item is changing filters and cleaning external components. Most buildings are operated such that these tasks are done only when their neglect causes a problem. However, a clogged filter puts unnecessary strain on the HVAC system fans and heating and cooling system, and consequently raises energy costs. It also usually creates occupant discomfort.
The volume and type of food cooked in the kitchen determines how frequently an exhaust system needs cleaning and maintenance. Select an appropriate schedule for HVAC maintenance by monitoring the rate of build-up in the exhaust filters and duct access doors for a least a month. This should provide enough information for specialists to suggest an ideal schedule for system cleaning and repair. Many professional building operators also put a pressure drop indicator on filters to indicate when they need maintenance.
Another key way of reducing system operating and maintenance costs is to educate site personnel in proper HVAC operation. Turning systems off at appropriate times, setting thermostats, and even simple things like closing doors can create significant annual savings and increased equipment life. However, major equipment maintenance tasks should be left to professional maintenance contractors.
For more information about the benefits of ventilation systems, please contact us for a copy of an EPRI performance or ventilation report.
Types of Ventilation (Cooking):
A back-shelf ventilator is the best alternative in kitchens where low ceiling height or a lack of space prevents use of an overhead canopy. The unit is installed at the rear of the cooking equipment, closer to the actual cooking surface than an overhead canopy. Back-shelf units are not intended for heavy production usage, nor for use with high-exhaust-surge cooking equipment like char-broilers.
The typical minimum clearance (distance between the cooking surface and filters) is 18 to 25 inches. This distance prevents overheating that can cause accumulated deposits to bake on the vent filters. Excessive temperatures also tend to vaporize grease, which allows it to pass through the filter and deposit on internal system components. This increases cleaning and maintenance costs.
The hood of the back-shelf ventilator should extend from the wall a distance of at least 24 inches, but be set back enough from the front to allow adequate head clearance for cooks. Cooking equipment should extend no more than 36 inches.
Canopy hoods are installed either against a wall or above cooking equipment (called island canopies). The length and width of the hood face should equal the total dimensions of the cooking appliance plus an appropriate overhang on each side. This overhang amount depends on the hood style and the kitchen appliance used.
A wall canopy with side curtains is possibly the most efficient design for capturing contaminated air. An island canopy hood is the largest type but is quite susceptible to cross-drafts and air spillage. Side air curtains prevent cross-drafts. Also, back paneling or tempered glass may be installed to produce a rear wall effect.
Eyebrow style hoods are mounted directly to ovens and dishwashers to catch effluents. This hood type can be designed to operate only when appliance doors are opened or at certain points in the cycle.
Heat Recovery Devices
An excellent energy-saving option, heat recovery devices are usually designed to harvest and recycle waste heat from kitchen equipment for use in space and water heating.
Heat recovery devices are becoming more common. These devices are usually designed to recover and recycle energy for space heating and water heating. Without recovery units, this energy would be wasted.
All energy recovery systems operate on the same principle. Energy is recovered from outgoing air exhaust using a wheel, coil, pipe, or other device. The recovered energy is transferred to incoming air or water. Air-to-air heat recovery systems rely on the fact that air leaving the kitchen is hotter than incoming fresh air for most of the year. In this design situation, incoming air is warmed. Where the air leaving the kitchen is colder than outside air, it is cooled. This reduces the load on the primary heating and cooling system, reducing energy costs.
Another common energy recovery system captures waste heat from on-site refrigeration units or kitchen exhausts to produce hot water. Such a system is called a heat pump system and is available either as an option in the refrigeration system or as an add-on spot cooling system. Spot cooling systems are commonly specified for kitchens with inadequate cooling and are sold on the basis that they provide economical cooling and “free” hot water.
There are also many other types of heat recovery devices on the market including rotary or “heat wheel” regenerators, air-to-air plate-type exchangers, heat pipes, and liquid “run-around” coils. Predicting the cost performance of these systems and properly implementing them into a kitchen HVAC design is work for a professional and should not be based on advertising or equipment supplier claims. All of these designs have proven cost effective in certain situations when properly incorporated into the overall kitchen design. However, all of these designs have also failed when not properly integrated into the kitchen design.
Introducing make-up air into a kitchen to produce a completely comfortable environment is very difficult. Achieving uniform comfortable temperatures, odor control, gentle air circulation, and minimal aggravating updrafts requires careful design and placement of wall registers, ceiling diffusers, and slotted ceiling panels.
Kitchen exhausts should be located away from the HVAC fresh air intake. If an existing HVAC system draws in odor-saturated exhaust, a baffle or barriers should be erected between the roof exhaust and the fresh air intake. These are just some of the reasons why kitchen design should be reserved for qualified professionals.
Wall registers are installed close to the ceiling, projecting return air across the ceiling in a straight line. The make-up air mixes with current air, circulating into the occupied zone. Problems often arise with wall registers because their high velocity operation may create additional updrafts.
Ceiling diffusers are normally flush mounted in the ceiling panels. These discharge supply air in a circular motion, outward along the ceiling. Where wall canopies are used, ceiling diffusers operate exceptionally well, if located a “sufficient distance” from all appliances and hoods (“sufficient distance” is defined as the equivalent of the maximum throw distance listed for the diffuser). When an island hood is used, it is difficult to apply a ceiling diffuser in a manner that effectively avoids updrafts.
Slotted ceiling panels provide a gentle uniform distribution of make-up air. Ideally, discharge air from ceiling slots should penetrate to face level at the rate of 20 to 25 feet-per-minute. In a properly designed system, return make-up air should barely affect the overall ventilation process.
The pass-over hood configuration is used over counter-height equipment where a pass-over capability is required. That is, prepared food is passed over from the cooking surfaces to the serving side.
Pollution Control Devices
Many local environmental ordinances require installation of pollution control devices with kitchen exhaust systems, especially where char-broilers or other smoke-generating cooking equipment is used. Two devices commonly implemented for “pollution control” are electrostatic precipitators and fume afterburners. Both are installed within the exhaust system and are essential in reducing air pollution.
Ventilation Study – Electric and Gas Griddles
As part of a larger study to identify optimal designs for commercial kitchen appliances, researchers tested one electric griddle and one gas griddle in operation with two hood types: an exhaust-only, wall-mounted canopy hood and a custom-engineered backshelf hood.
These tests revealed the following:
- The cooking capture and containment (C&C) flow rate under a canopy hood for the electric griddle is 241 scfm/lf, 13% lower than for the gas griddle, 40% lower than the 400 scfm/lf building code value, and 7% lower than the 260 scfm/lf Underwriters Laboratories (UL) listing.
- The cooking C&C flow rate under a custom-engineered backshelf hood for the electric griddle is 100 scfm/lf, 9% lower than for the gas griddle, 67% lower than the 304 scfm/lf building code value, and 26% lower than the 136 scfm/lf UL listing.
- The idle C&C flow rate under a canopy hood was 26% and 32% less, respectively, than the cooking C&C flow rate for gas and electric griddles, and was 0.5% and 22% less, respectively, under the backshelf hood.
- At the cooking C&C flow rate, the electric and gas griddles required about 60% lower flow under the backshelf hood than under the canopy hood. These results indicate that custom-engineered backshelf hoods can operate with exhaust flows about 65% below code values, and that electric griddles with both hood types require about 10% less exhaust than gas units. Designers should apply site-specific data when evaluating equipment options.
To help electric utilities and the food service industry minimize commercial kitchen exhaust hood operating costs, EPRI is undertaking a series of tests to determine the exhaust requirement for a wide range of food service equipment and ventilation hoods. The exhaust requirement is the air flow needed to capture and contain cooking products and heat. Findings compare actual exhaust requirements with building code and UL levels. The ventilation tests described here examined electric and gas griddles operating under a wall-mounted canopy hood and under a custom-engineered backshelf hood using American Society for Testing of Materials (ASTM) standard method production conditions.
Test Equipment and Conditions
Both griddles measured 28 in by 3 ft. The electric griddle was rated at 17.1 kW and the gas griddle at 90,000 Btu/h.
The canopy hood, an exhaust-only, wall-mounted type, was 5-ft wide by 4-ft deep and UL listed at 260 scfm/lf for cooking operation. The backshelf hood, a custom-engineered, exhaust-only type, was 3.4- ft wide by 3.5-ft deep by 5-ft high and was UL listed at 136 scfm/lf for cooking operation. Both hoods had three nominal 20-in by 20-in standard baffle filters.
For each test, researchers positioned the griddle under the hood in accordance with ASTM F1275-95 and performed the tests using ASTM F1704-96. The temperature of the griddle was set to a calibrated 375°F.
The project team evaluated C&C with visualization techniques aided by a smoke generator. They ran each test a minimum of three times in a consecutive series to attain statistical certainty as prescribed in ASTM F1704-96.
Figure 1 shows C&C flow rates for electric and gas griddles operating under both canopy and custom backshelf hoods, as well as flow requirements under two specification options. Operating under a canopy hood, the electric griddle’s measured cooking C&C flow rate is 241 scfm/lf, 40% lower than the rate required by building codes and 7% lower than that listed by UL. The idle C&C flow rate is 165 scfm/lf, 32% lower than the cooking rate. The gas griddle’s measured cooking C&C flow rate is 276 scfm/lf, 31% lower than the rate required by building codes and 6% higher than that listed by UL. The idle C&C flow rate is 203 scfm/lf, 27% lower than the cooking rate.
Operating under a custom-engineered backshelf hood, the electric griddle’s measured cooking C&C flow rate is 100 scfm/lf, 67% lower than the rate required by building codes and 26% lower than that listed by UL. The idle C&C flow rate is 78 scfm/lf, 22% lower than the cooking rate.
The gas griddle’s measured cooking C&C flow rate is 110 scfm/lf, 64% lower than the rate required by building codes and 19% lower than that listed by UL. The idle C&C flow rate is 109 scfm/lf, 0.5% lower than the cooking rate.
- Commercial Kitchen Ventilation Performance Report, Electric Griddle Under Canopy Hood, EPRI TR-106493-V4, July 1996.
- Commercial Kitchen Ventilation Performance Report, Gas Griddle Under Canopy Hood, EPRI TR-106493- V3, July 1996.
- Commercial Kitchen Ventilation Performance Report, Electric Griddle Under Custom Engineered Backshelf Hood, EPRI TR-106493-V6, July 1996.
- Commercial Kitchen Ventilation Performance Report, Gas Griddle Under Custom Engineered Backshelf Hood, EPRI TR-106493- V5, July 1996.
- Too Much Hot Air: Reexamining Commercial Kitchen Ventilation Systems, EPRI TB-105709, October 1995.
- Minimum Energy Ventilation for Fast Food Restaurant Kitchens, EPRI TR-106671, July 1996.
- Standard Test Method for Performance of Commercial Kitchen Ventilation Systems, ASTM F1704-96.
- Standard Test Method for the Performance of Griddles, ASTM F1275-95.