Articles by John Tomczyk
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. Read More
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. Read More
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.
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.
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°.
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. Read More
August 6, 2007
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.
July 2, 2007
When dealing with a residential cooling system, modulating compressor capacity - along with a variable-speed blower motor for the conditioned air - will deliver much tighter temperature control with a reduced humidity level within the conditioned space than a standard cooling system.
June 4, 2007
This article deals with low ambient head pressure controls
containing charged domes. Their function is to keep a proper condensing
pressure at the metering device for proper feeding of the evaporator. This is
the second of a two-part series that began in the May 7 issue. Read More
May 7, 2007
This article deals with head pressure control
valves that work in conjunction with one another in cold ambient conditions.
They keep the proper condensing pressure at the metering device for proper
feeding of the evaporator. Read More