Refrigerated display cases, walk-in freezers, and coolers are used in a variety of businesses, including grocery and convenience stores, food service facilities, warehouses, lodging and more. Although critical to operations, refrigeration systems use a significant amount of energy. Refrigeration control technologies can reduce energy and maintenance costs while extending equipment life.
Refrigeration controls use sensors and embedded algorithms or instructions to run system components more efficiently. Here are six common control technologies for display cases, walk-in coolers and freezers.
1. Anti-sweat heater controls
Anti-sweat heaters prevent moisture from forming on glass doors in refrigerated display cases. Left uncontrolled, these units run constantly, yet they are only needed for short periods. With humidity-sensing controls, heaters run less often, reducing the load on the refrigeration system. They are relatively inexpensive, and easy to install and maintain.
2. Variable frequency drives
Operating fan and compressor motors at full speed when minimal load is required wastes energy. VFD technology uses sensors to operate fans and compressors at the speed required, reducing the need to start and stop motors. In addition to saving energy, VFDs reduce equipment wear and improve product quality by minimizing variation in operating temperature.
3. Desuperheater controls
Superheat is heat stored in the refrigerant vapor when it is heated above its evaporation temperature. A desuperheater heat reclaim device in series with the normal condenser cools the refrigerant only to the saturation point; no condensing takes place in the desuperheater. This is controlled by a three-way heat reclaim valve. A desuperheater can remove about 10% to 30% of the total heat that typically would have been rejected by the condenser. This reclaimed heat is used for space or water heating.
4. Defrost controls
Defrost controls can save up to 6% of refrigeration system energy use. Demand controls — considered the most effective — initiate defrosting in a variety of ways, including measuring the temperature or pressure drop across the evaporator, measuring frost accumulation and sensing humidity. All of these methods, if used properly, are more effective than using a simple timer to initiate defrosting.
5. Floating head pressure
Refrigeration systems commonly use fixed head pressure control, in which condensing pressure is maintained by a condenser fan, regardless of the system load. Allowing the pressure to vary or float based on outdoor conditions helps to improve system efficiency while extending equipment life.
6. Lighting controls
Lights in refrigerated units often operate 24 hours a day, or during operating hours. Energy-efficient LED lighting combined with occupancy sensing controls provides energy savings and reduces maintenance. LEDs last longer than many conventional lighting technologies and provide excellent cold temperature performance. Their instant-start capabilities make them a perfect fit for occupancy controls.
Selecting the right control strategy depends on the application. Consult with your equipment vendors to find the right type of control technology that best fits your needs.