Demand-Controlled Ventilation for Kitchen Hoods Helps Restaurants Run at Peak Efficiency

Food service providers increasingly understand the need for varying airflows in kitchens throughout the day. This is evident as demand-controlled kitchen ventilation (DCKV) for exhaust hoods becomes more popular in commercial kitchen ventilation system design.¹

Greater integration capabilities of kitchen ventilation systems with dining room systems also open the door for more restaurant efficiency. As such, restaurants can use best practices gained from DCKV application on their heating, ventilation and air conditioning (HVAC) systems for demand ventilation in kitchens. Restaurants particularly can utilize additional system components, such as fan optimizers or optical and temperature sensors, to better control exhaust airflow in the kitchen for maximum energy efficiency.

Reap the rewards with DCKV operations
Restaurants can reduce high energy consumption, improve efficiency and lower monthly utility bills by installing DCKV systems with optic and temperature controls on kitchen grill hoods. State regulations such as Title 24, also known as the California Building Standards Code, also bring more attention to the use of DCKV systems. Restaurants that have higher occupancy loads consider DCKV to improve operations. In fact, DCKV systems can reduce exhaust costs by up to 50% and are available for both new equipment and as retrofits for existing kitchen range hoods.²

Kitchen hoods traditionally run at a constant rate, regardless of whether cooking is taking place. In contrast, DCKV applied on kitchen range hoods use sensors and microprocessors to respond to the actual, real-time exhaust needs of a kitchen. When commercial kitchen equipment, such as grills under an exhaust hood, is not in use, the kitchen exhaust controller can adjust fan speeds to reduce the amount of exhaust and make up air. Similarly, the DCKV fans also run at a greater operational level to reduce excess smoke and vapors caused by a kitchen’s full-load cooking and decrease speed levels when cooking is reduced.

Preserve energy with complementary sensors
The progression from a two-speed fan control system to variable frequency drives (VFDs) for exhaust temperature helped open the door for temperature and optical sensor adoption in restaurant kitchens.

Temperature sensors, which detect heat from the cooking operations, automatically signal the control to start the fans, which provide varying speeds based on cooking load or time of day. Combined use of optical and temperature sensors helps measure smoke, steam and heat caused by heavy cooking operations. Added optical sensors further detect cooking activity that takes place under the exhaust hood to further enhance performance.³

To more effectively integrate kitchen hoods, fans and speed controls, restaurants should consider a few key questions,⁴ which include:

• Are the fans supplied with a direct-drive speed controller or does a separate VFD need to be specified?
• How will the system maintain air balance?
• What will verify hood performance at the various speeds?

Addressing such questions can specify a restaurant's DCKV needs but also help them set realistic expectations for adequate exhaust ventilation rates.

Gain financial restaurant benefits
DCKV systems can mean big savings for restaurants. With the help of PG&E's Food Service Technology Center (FSTC), San Francisco-based Tadich Grill implemented a DCKV system, resulting in a $12,500 installation rebate and expected year-over-year savings of more than $4,500 on operating costs.

Advanced systems can lead to annual fan energy savings of between $1,500 and $10,000, leading to a return on investment in less than one year.⁵ Beyond those direct savings, DCKV systems can save restaurants 15% to 40% on their heating and cooling costs, since the fans won’t affect ambient temperatures as heavily. By exhausting less air, less make up air will need to be continued.

Comal Restaurant in Berkeley, Calif., also instituted a DCKV system and found the rebates on installation and overall savings on utilities a help to its bottom line. The $1,800 installation rebate, along with reduced monthly utility bills, made the system essential to Comal's overall energy- and cost-efficiency plan.

Rebates and incentives for energy-efficient food service equipment, such as those from PG&E, will continue to be an asset for restaurants and other food service providers. Restaurant owners and operators and food service providers can also turn to PG&E’s FSTC for more comprehensive information about energy use and efficiency.⁶

Implement DCKV for greater energy efficiency
DCKV system adoption in restaurants will continue to grow as it helps reduce building over-ventilation, save on fan energy and lower heating and cooling costs. Restaurant owners and managers can work with a contractor to enhance efficiency in the kitchen with complementary ventilation system components.

Food service providers can reference "The Complete Guide to Working with a Lighting or HVAC Contractor" eBook to find out how HVAC technicians can help them improve their kitchen workflow and improve energy and cost efficiency.

1. Fisher-Nickel Inc.
2. ENERGY STAR
3. ASHRAE
4. ASHRAE
5. U.S. Department of Energy
6. Pacific Gas and Electric Company