Technicians often use wallet pressure/temperature (P/T) cards in working with new blends, which requires manual math calculations to interpolate table entries. Sometimes, they use P/T correlation to identify or confirm the refrigerant in the system. This process is mistake prone and not precise enough to distinguish between similar replacement blends, possibly leading to accidental refrigerant mixing.

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

Air conditioning systems often get very little attention to their subtle problems until they become compressor failures. But R-22 systems have the highest compressor failure rates! Many refrigerants contain the element fluorine in their structure. In the presence of minute amounts of moisture and air, reactions create hydrofluoric acid, capable of eating through glass. Since motor windings are silica based, their insulation is extremely vulnerable. For prevention, subtle problems such as liquid floodback from a plugged evaporator coil, high superheat from plugged condensers, or short charged systems must be spotted early on and consistently. Again, these problems are difficult to see using Bourdon tube gauges.

Fortunately, modern electronic tools already available can address these shortcomings by providing accurate pressure readings in an easily readable form for the technician. Other important features 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. They all combine to make diagnostic work quicker and more accurate, with less chance of human error.

Precise view of the pressure fluctuations allows technicians to quickly spot out-of-envelope operating conditions and the exact nature of the problem. Symptoms such as a dirty condenser/evaporator, TEV hunting, or small amounts of liquid floodback, typically difficult to find with Bourdon gauges, all have small sub-psi pressure fluctuation patterns. With the right tool, these patterns are clearly seen, so your technicians make the proper repair right away without guesswork.

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.

Automatic SST display eliminates one error-prone step of the important superheat calculation. Further, after refrigerant substitution, even drop-in replacements like R-407C for R-22 requires some metering adjustment. Sometimes neglected by the substituting technician, the 5 degrees F of superheat difference is significant and easily missed by subsequent service workers. If the technician sees the small SST change, he would make the adjustment and the compressor may be saved from seizing or burnout. These situations are similar across different applications, from residential to commercial rooftops to supermarkets.

Finally, do not underestimate the image of your firm in your customer's mind. Combined with professional, courteous staff, the use of modern, well-kept tools leaves a positive impression about your professionalism, helping them remember you the next time they need service.

Air conditioning and refrigeration systems today are vastly different than those with the classic refrigerants from years ago. Technicians need the proper tools to speed up installation and troubleshooting, to offset the extra information and possibilities to consider. These needs can be met with modern electronic tools that give accurate information quickly, such as the Digital Refrigeration System Analyzer (DRSA) from Digi-Cool Industries. Similar to investments in information technology and communication, contractors need to invest in state-of-the-art HVACR tools to remain competitive in the changing service landscape.

Doug Lockhart, A.Sc.T, is an HVACR contractor and founder of Digi-Cool Industries Ltd., Duncan, British Columbia. For more information, e-mail info@digi-cool.com or visit www.digi-cool.com.

Publication date: 08/09/2004