This is the first of three columns on systematic air conditioning troubleshooting and diagnostics. It will deal with airside and the evaporator. In a/c system diagnostics, a service technician must realize that system problems fall mainly under two major categories: airside problems and refrigerant cycle problems.

It is of utmost importance for service technicians to understand voltage troubleshooting when servicing HVAC and refrigeration equipment. The majority of service problems are electrical problems, which usually cause mechanical problems. This article illustrates how to voltage troubleshoot using a voltmeter.

This column explores how a restricted metering device will affect system performance and efficiency. The system is a commercial refrigeration system employing a receiver and a thermostatic expansion valve (TXV) as the metering device. The refrigerant is R-134a.

My Jan. 14 column in The NEWS focused on system overcharges. This column will look at an undercharge of refrigerant. In the example to be used, we will look at a medium-temperature refrigeration system running on HFC-134a and having a thermal expansion valve (TXV) and liquid receiver.

Many technicians have a tendency to add refrigerant to a refrigeration system simply because it is not cooling to its potential. Often, this overcharges the system with refrigerant and can make matters worse.

As you might recall, my Nov. 5 column focused on a restricted liquid line after the receiver. In this column, we will look at local cold spots or frost where the restriction occurs and issues related to bubbles in a sight glass.

The problem we are going to deal with in this and next month’s columns is a restricted liquid line after the receiver. In this column, we will look at eight possible symptoms. In the Dec. 3 column, we will look at a couple of other issues. For both columns, we will use a service checklist that shows that the system has a TXV valve, filter drier, and sightglass. The refrigerant is R-134a.

Customers have been complaining for three weeks of warm products in a low temperature, glass door, reach-in freezer. The storeowner inspects the thermometers in the case and notices that the temperature will not pull down below 15°F. The temperature has been 15° for about a week, but ideally it should be 0°.

Discus compressors are refrigeration compressors used in supermarkets, walk-in coolers and freezers, and industrial applications. They range in horsepower from 5 to 60-hp. Discus compressors are available with capacity modulation from 10 to 100 percent. This provides the ability to match capacity to the desired load of refrigeration equipment.

The compressor’s discharge temperature can tell the service technician what is going on inside a refrigeration or air conditioning system. The compressor’s discharge temperature is a reflection of the hottest part of a refrigeration system, and there are limits as to how hot a discharge temperature should be. This article will explore discharge temperatures and their limits.