HVACR systems that operate using a vapor-compression cycle generally comprise a compressor, a condenser, an expansion valve and an evaporator interconnected by a line having an interior within which a refrigerant fluid is circulated. Although this technology is mature and is currently used in a wide variety of commercial and residential applications, malfunctions can arise as a result of leaks in the system or failure of one or more components. In many instances, the malfunction may not be catastrophic, e.g. wherein the system ceases to heat or cool altogether, but may result in a gradual or progressive decrease in performance and/or efficiency that can nevertheless create spoilage of foodstuffs and other inventory, for example, or other problems.
Periodic maintenance of HVACR systems can be time consuming, expensive and in many cases unnecessary at the time performed. Recognizing that a failure to maintain such systems will eventually cause a problem, the issue becomes how often such maintenance should be performed and what should be done. Approaches that rely solely on the passage of time are often ineffective and ignore the specific requirements of a particular installation and/or type of system.
Automated preventative maintenance devices for HVACR systems have been proposed, such as disclosed, for example, in U.S. Pat. No. 5,596,507. The device disclosed in the '507 patent relies upon a number of temperature sensors and electrical current sensors to detect a variety of operating parameters of the system, and to provide inputs to a computer capable of analyzing the data and identifying potential trouble spots in the system that may need maintenance. While systems of this type may be effective, they are not economically feasible for residential applications and many smaller commercial operations.