The present invention relates to a control system for a refrigerated merchandiser. More specifically, the present invention relates to a control system that cools product in the refrigerated merchandiser within a predetermined temperature range based on a freezing temperature of the product.
In conventional practice, supermarkets and convenience stores are equipped with refrigerated merchandisers that have cases to store and present product (e.g., beverages) on shelves in a product display area available to customers. Typically, refrigerated merchandisers include a refrigeration system that directs cool, refrigerated air into the product display area to keep the product cold. However, existing merchandisers direct the refrigerated air directly toward the product. In existing merchandisers that include multiple vertically-stacked shelves, the refrigerated air is directed toward the uppermost shelves. This often causes the product on the uppermost shelves to be relatively cold and the product on the lowermost shelves to be relatively warm. These merchandisers compensate for the warm product on the lower shelves by decreasing the temperature of the refrigerated air. However, decreasing the temperature can freeze the product stored on the upper shelves.
Existing cases are often designed to store large quantities of product on the shelves without regard to airflow patterns within the case that are necessary to adequately cool the product. These large quantities of product often impede the flow of refrigerated air through the case, which causes the temperature of the product to be substantially variable at different areas of the case. In addition, the airflow within these cases can be substantially turbulent, further contributing to a relatively large temperature distribution of the product.
Some existing cases include a mechanical thermostat to control the temperature of the product. These mechanical thermostats often have a wide temperature differential between “ON” and “OFF” states due to the lack of precision inherent in these mechanical thermostats. As a result, the temperature of the product fluctuates over a relatively large temperature range, which can adversely impact the quality of the product.
Some cases use the temperature of the air in the product display area to represent the temperature of the product. However, the temperature of the air in the product display area does not provide an accurate indication of the product temperature. The temperature of the air in the product display area can be adversely affected by door openings and defrost of the refrigeration system, which can warm the air in the case. Opening the door and defrosting the refrigeration system often increases the temperature of the air surrounding the product, but does not necessarily change the temperature of the product itself.