Articles by John Tomczyk

The Professor: Diagnosing Air Conditioning Systems

June 2, 2008
This is the second of three columns on systematic air conditioning troubleshooting and diagnostics. The first appeared in the May 5 issue of The NEWS. The third part will appear in the July 7 issue. This article deals with modern evaporator and condenser designs to meet the new minimum 13 SEER requirements.
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The Professor: Diagnosing Air Conditioning Systems

May 5, 2008
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.
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The Professor: Troubleshooting With Voltmeter

March 31, 2008
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.
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The Professor: Restricted Metering Device

March 10, 2008
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.
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The Professor: Refrigerant Undercharge

February 4, 2008
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.
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The Professor: System Overcharge

January 14, 2008
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.
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More Systematic Troubleshooting

December 3, 2007
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.
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Systematic Troubleshooting

November 5, 2007
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.
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Cold, But Not Enough!

October 1, 2007
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°.
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Discus Compressors

September 3, 2007
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.
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