Refrigeration systems often support perishables vital to your customer's business. The contractor becomes a vital link to a customer's success.

Compared with installation and maintenance, repairs are more demanding because they are unpredictable. Responding quickly and effectively to a customer's crisis can directly lead to repeat business and recommendations. For the same reason, repair work is challenging to manage in terms of cost and customer satisfaction.

While electrical wiring and air circulation continue to be sources of headaches, more problems in today's refrigeration systems are in the refrigerant circuit. The chemistry between the new refrigerant blends and oils is relatively new to the industry, causing more unexpected incompatibilities and service mistakes.

As a result of mistakes by inexperienced service technicians, many systems can develop toxic brews in their refrigerant circuits. A thorough diagnostic often is needed to make sure these problems are found on the first service call.

Technicians often use wallet pressure/temperature (P/T) charts that require math calculations to interpolate table entries when working with new blends.

Sometimes they use a P/T correlation to identify or confirm the refrigerant in the system. This process is prone to mistakes and not precise enough to distinguish between similar replacement blends, possibly leading to accidental refrigerant mixing.

Bourdon tube pressure gauges, at 2-percent to 3-percent accuracy, do not have the precision necessary to allow technicians to make accurate, timely, or financially prudent decisions about system performance. Technicians sometimes misrepresent the actual reading by adding their own safety factors. Sometimes technicians head in the wrong direction with poor diagnostic information, only to return later to re-evaluate their work and explain the previous problem to the customer.

Air conditioning systems often receive very little attention for any subtle problems that may be present, until there are compressor failures.

Many refrigerants contain fluorine in their structure. In the presence of minute amounts of moisture and air, reactions may create hydrofluoric acid, which is capable of eating through glass.

Motor winding insulation is extremely vulnerable because it is silica-based.

In preventive work, subtle problems such as liquid floodback from a plugged evaporator coil, high superheat from plugged condensers, or short charged systems must be spotted early.

Modern electronic tools are designed to provide accurate readings in easily understandable forms. Pictured is the Digital Refrigeration System Analyzer (DRSA) from Digi-Cool.

Help Is On The Way

Other features to look for in such tools include precise real-time saturated suction temperature (SST) displays, clear display of pressure dynamics useful in diagnostics and tuning, vacuum display, and durability in field use. These features combine to make diagnostic work quicker and more accurate, with less chance of human error.

A precise view of pressure fluctuations allows technicians to quickly recognize out-of-envelope operating conditions and the exact nature of the problem.

Symptoms such as a dirty condenser and/or evaporator, thermal expansion valve hunting, or small amounts of liquid floodback all have small, sub-psi pressure fluctuation patterns. Using the proper tool, the technician can make the correct repair immediately.

An integrated vacuum and pressure gauge is handy for everyday troubleshooting. Typically, readings in inches of mercury are sufficient. A micron vacuum gauge should be used when eliminating moisture or checking for system leaks using a deep vacuum draw.

An automatic SST display eliminates some of the guesswork of the important superheat calculation. Further, after refrigeration substitution, even replacements like R-407C for R-22 require some metering adjustment.

Sometimes neglected by the technician, the 5 degrees F of superheat difference is significant and easily missed in subsequent service work. If small SST change is sought, the technician should make the adjustment, which could prevent the compressor from seizing or burnout.

These situations are similar across different applications, from residential to commercial to supermarket installations.

Armed with the proper tools and knowledgeable staff, a contractor can overcome such challenges, while improving competitiveness and customer satisfaction.

Finally, do not underestimate the visual image your firm leaves in your customers' minds. Combined with professional, courteous staff, the use of modern, well-kept tools leaves a positive impression about your professionalism, helping them to re-member you the next time they need service.

Doug Lockhart is a contractor and technician, as well as founder of Digi-Cool Industries. For more information, visit www.digi-cool.com.

Publication date: 02/07/2005