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50 • FOODSERVICE EQUIPMENT & SUPPLIES • MARCH 2017 Technology Center. Testing has shown that these panels can encourage an energy reduction of 30 percent. Engineers continue to encourage specification of side panels on kitchen exhaust hoods as standard, rather than best practice. Even very small side panels can improve exhaust hood performance, according to the PG&E FSTC. In addition, many aerodynamic features have been integrated into the design of leading brands of listed hoods, including flanges or lips along the hood's lower edge, air jets, resized filters, eliminated filter shelves, wall-mounted canopy hoods, and backshelf, pass-over or eyebrow hoods that can be mounted at different heights and horizontal positions relative to the cooking equipment. According to the PG&E FSTC's design guides, developed in part by Southern California Edison, a single-island canopy hood requires more exhaust than a wall-mounted canopy hood, and a wall-mounted canopy hood requires more ex- haust than a proximity (backshelf) hood. The fundamental steps in the design of a CKV system include: 1) establish location and "duty" classifications of appli- ances including menu effects, and determine preferred appli- ance layout for optimum exhaust ventilation; 2) select hood type, style, and features; 3) size exhaust airflow rate; and 4) select makeup air strategy, size airflow and layout diffusers. Laboratory testing of different combinations of appliances has demonstrated that minimum capture and con- tainment rates vary significantly due to appliance type and position under the hood. For example, a heavy-duty appli- ance at the end of a hood is more prone to spillage than the same appliance located in the middle of the hood. Optimizing makeup air is another important factor in designing a hood installation for maximum performance and efficiency, according to a design guide published by the California Energy Commission and the PG&E FSTC. Use of air curtains, front-face air supply, backwall supply (rear discharge), perforated perimeter supply and four-way ceiling diffusers can all introduce makeup air in proper ways with the right implementation. In addition, integrating kitchen exhaust systems with building HVAC units can also help operators achieve opti- mum performance and energy efficiency, as can optimizing the position of equipment underneath the hood. Overhang and rear gap are important parts of that determination. According to a fourth design guide published by the PG&E FSTC, an increase in overhang will significantly improve the ability of a wall-canopy hood to capture and contain cooking plume. "Something as simple as pushing appliances to the back wall can save as much as 40 percent on air flow rate," says Swierczyna. A large overhang is also beneficial for appliances that create plume surges when doors or lids are opened, such as convection and combination ovens, steam kettles, com- partment steamers and pressure fryers. Specifying a deeper hood (for example, 5 feet versus 4 feet) will directly increase overhang, provided appliances are situated as far back as pos- sible in the hood. This is an effective solution for the oven or combination oven and its "door-opening" challenge. OTHER EMERGING TECHNOLOGIES Heat-recovery devices have started to appear on the horizon in the form of emerging commercial kitchen ventilation technologies beyond demand control. Some manufacturers are testing systems that can actually grab heat released from the exhaust duct — not just from other appliances — which can then be used to preheat water for water heaters, according to Swierczyna. Swierczyna and other engineers continue to test other systems that can preheat the air that comes into the res- taurant or operation for makeup air heating. By recover- ing heat with copper tubes from a fryer flue, for example, and moving it to a coil in a makeup air unit and blowing outside air over the warm or hot copper tubes, it warms up the makeup air to prevent the gas or electric furnace from working as hard to maintain the thermostat's set point temperature. A third heat-recovery technology captures the steam and plume released from dishwashers through a similar coil sys- tem. "Before you open the door, you would wait 30 seconds while cold water runs through the coil, picking up heat from that plume," Swierczyna says. "That water goes back and heats the cold water coming into the dishwasher so you're able to preheat that water without having to hook up directly to a hot water line anymore. By using all of that plume through a heat recovery system, you can go with a smaller hood or no hood at all in the dishroom." Though ventless is becoming more popular in certain situations, there are still issues, according to Swierczyna. "In small spaces, ventless equipment can create an increase in heat and humidity," he says. FE&S