Definition: Refrigeration controls are devices used inside refrigerated units to regulate the environment in the unit. Temperatures are controlled within a certain tolerance that can vary. Newer controls provide alarms and logging for HACCP compliance. They let users know if temperatures are out of balance or if a power outage occurs. Today's refrigeration controls focus on energy efficiency, accuracy and ease of operation. For manufacturers, electronic controls offer easier inventory management, and for kitchen staff, these controls are easier to operate due to their simple up and down buttons that change case temperatures.
Benefits: Newer refrigeration controls have consolidated a number of electromechanical controls, including the thermostat, defrost timer and terminator. Benefits of this consolidation include increased energy management, better temperature accuracy, easier inventory management due to fewer parts, simple push-button operation and the ability to network refrigerated cases together. These electronic controllers also offer more accurate defrost management, which further enhances food quality and can reduce overall electrical consumption by 25%. When the defrost engages, it determines the time of defrosting with each cycle and gets terminated by a sensor on the evaporator when the unit's interior gets to a certain temperature. This feature keeps temperatures stable so food doesn't suffer from increasing and decreasing defrost temperatures. Older standard controls run the same defrost cycle constantly. Also, because the new refrigeration controls have one part, as opposed to three or four, these systems are easier to maintain and service. While systems in the past relied on a metal sensor that expanded and contracted, today's more accurate sensors keep food at constant temperatures, generally varying by no more than one tenth of a degree. This enhances food quality and reduces shrinkage. These controls also feature an easy-to-read digital display on the outside of the case for temperature monitoring.
Types of Systems: Two types of control systems - capillary or cap tube and expansion valve - are available. The systems are reminiscent of the air conditioning industry, where the primary controls used to be pneumatic, using air pressure. A shift occurred in the late '70s and early '80s, and today electronic air conditioning controls well outsell pneumatic controls. Many say this is similar to what is currently happening with refrigeration controls.
A cap tube is a refrigerant flow control that feeds liquid refrigerant to the evaporator based on the pressure differential between the inlet and outlet of the tube. As such, it does not respond well to changes in the refrigeration load and is usually restricted to applications that have relatively constant loads. The most common example of such an application is the domestic refrigerator. Cap tubes are ideal for such an application, since the load is nearly constant year-round. They are reliable because there are no moving parts. This system utilizes a coiled capillary tube that is typically between 5 and 10 in length. The fixed length of the tube depends on the case design.
Expansion valves control the amount of refrigerant fed to the evaporator in direct proportion to the heat load on the evaporator. As a result, systems employing TXVs always operate at near optimum efficiency levels. This results in faster pull-downs, such as after a defrost or any time there is an abnormally high heat load on the operating system.
TXVs also have the benefit of shutting off completely whenever the compressor is off. This prevents refrigerant pressure equalization during the off cycle and further improves system efficiency as compared to a cap tube system. Expansion valves work off of a bulb.
New Features: Intelligent defrost heaters thaw ice off of cap tube coils, offering greater energy efficiency. There are cases that when ice builds on the coil, the unit will go into defrost to energize the coils. Newer controls can alert users if the compressor needs replacing or if the relay is about to fail. These systems proactively troubleshoot for users, making maintenance planning easier. The controls also can be connected to the internet, automatically alerting maintenance people of any problems. This helps reduce downtime and profit loss from spoiled food. Recent innovations allow for the integration of refrigeration controls with HVAC, lighting and other store systems. Refrigeration controls that hook up to facility management programs or computers can automatically log temperature data, which offers verification from a food safety standpoint. For instance, if there is a question about a customer's foodborne illness, computer logs detailing the case temperatures will confirm that food was held safely. Also, more energy-efficient LED bulbs are being used for lighting.