When to Replace an Air Curtain
By Lisa White, contributing editor -- Foodservice Equipment & Supplies, 10/16/2008 6:05:00 AM
Air curtains are units that employ a controlled stream of air aimed across an opening to create an air seal. Also known as air doors, air curtains separate different environments, while allowing a smooth, unhindered flow of traffic and unobstructed vision through the opening.
Because air curtains help to contain heated or conditioned air, they can provide sizeable energy savings and personal comfort when applied in commercial settings. Air curtains also can stop the infiltration of flying insects.
The two major types of air curtains are recirculating and non-recirculating. Recirculating air curtains, which are mainly used in entrances, emit air from a discharge grille on one side of the door opening, collect it through a receiving grille on the opposite side, and return it through ductwork to the discharge grille. Recirculating units create a non-obtrusive, wide stream of low-velocity air.
Non-recirculating air curtains are more widely used than the recirculating type because they are easier and less costly to install and have lower maintenance costs. With non-recirculating units air brought in through an intake enters the fan housing and is accelerated by a fan. This fast-moving air goes into a plenum, which allows for an even distribution of air along the full length of the discharge nozzle. Aerofoil-shaped vanes in the nozzle create a uniform air stream with a minimum of turbulence.
The air discharged through the nozzle creates a jet stream to the floor. These nozzles are typically adjustable to aim inward or outward up to 20 degrees from the opening.
Foodservice operators can mount non-recirculating air curtains horizontally above the door or vertically on one or both sides of the door, depending on the space available and the height, width and physical characteristics of the opening.
The four non-circulating air curtain categories include Industrial Climate Control, Commercial Entrance, Insect Control and Cooler/Freezer.
Commercial entrance air curtains are becoming widely used in building entrances to reduce energy consumption and provide comfort. In the winter, they retain warm inside air and prevent the influx of cold air. They also can supply additional heat in the door area using optional electric, steam or hot water heaters.
In high-traffic doorways air curtains reduce the inflow of outside air. Newer units are quiet, compact and pay for themselves in a short time. Most units can function year-round and are adjustable for seasonal conditions using a multi-speed motor.
Insect control air curtains, also called “Fly Fans,” use a powerful stream of air that prevents insects from passing through. Most units have nozzles that can angle the air stream away from the area to be protected. U.S. Department of Agriculture and Federal Drug Administration standards call for an air stream 2” to 5” wide at the nozzle capable of producing a minimum velocity of 1600 fpm of air 3’ above the floor and across the entire door opening.
Air curtains are up to 85 percent efficient in controlling the flow of air through cooler and freezer doorways. In addition to providing substantial energy savings and increased safety, these units can increase the time between defrostings up to almost four-fold, depending on the freezer or cooler conditions. Because these air curtains maintain the cooler/freezer temperature right up to the doorway, product quality is improved, useful floor space is increased and the compressor life is extended.
Air curtains mounted above a door either on the interior or exterior, fit on doors ranging in size from 36” to 144” wide. These units also can be tandem-mounted side by side or custom-manufactured for doors up to 16’ wide and 20’ high.
Smaller units for drive-thru windows feature lower profiles and aesthetically appealing designs.
Air curtains are available in satin anodized-aluminum, bronze anodized-aluminum, stainless-steel, white-aluminum, powder-coated, plastic and custom-painted types.
Most units operate on either 120V or 230V. Heated air curtains offer electric, hot water or steam operation.
A variety of options are available, including remote control operation, variable speed controllers, motion detectors, programmable thermostats and time delay relays.
Other Air Curtain Applications
Although most foodservice operations use air curtains for insect and climate control, here are some other lesser-known applications.
Foodservice operators can use an air curtain to control dust and humidity as well as to help separate smoking and non-smoking areas. Air curtains have been used by oven openings for temperature control, saving up to 40 percent on total oven fuel consumption.
Air curtains also can dry both dishes and dipped fruit, in addition to helping control trash compactor odors.
Berner International Corp.
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