Articles by John Tomczyk

The Professor: Refrigerant Migration

June 7, 2010
Refrigerant migration is defined as refrigerant, either liquid or vapor, traveling to the compressor’s suction line or crankcase during the off cycle. During the off cycle, or especially during a long shutdown, refrigerant will want to travel, or migrate, to a place where the pressure is the lowest.
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The Professor: Frost on the Compressor's Head

May 3, 2010
Many service technicians believe that if there is frost on the compressor’s head, there is cause for alarm. This is simply not true. Frost is simply frozen dew. Consider a low temperature commercial refrigeration application operating with 7° of evaporator superheat and 40° of compressor superheat.
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The Professor: Compressor Overheating

April 5, 2010
My column in the March 8 issue of The NEWS dealt mainly with reciprocating compressors experiencing low head pressure and high suction pressure from bad valves. This column takes an in-depth look at high compression ratios that cause compressor overheating along with high compressor discharge temperatures.
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The Professor: Low Head Pressure, High Suction Pressure

March 8, 2010
Many servicemen experience service calls where the compressor has both a low head pressure and a high suction pressure. There are three main reasons why a reciprocating compressor will simultaneously have a low head pressure and a high suction pressure.
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The Professor: Oil Safety Controllers and Their Circuits

February 1, 2010
Oil safety controllers often come in two types: bellows (mechanical) and transducer (electronic). Bellows-type controllers sense crankcase pressure and oil pump discharge pressure, usually through some type of tubing, and then transmit the pressure to flexible bellows. Transducer-type controllers use a pressure transducer.
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The Professor: Net Oil Pressure

January 11, 2010
Many larger compressors in the refrigeration and air conditioning field have forced-oiling systems. These compressors are usually over 5 hp. They contain an oil pump located at the end of the compressor’s crankshaft. The crankshaft is actually connected to the oil pump and supplies power, which turns the oil pump.
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The Professor: Systematic Troubleshooting

December 7, 2009
The problem we are going to deal with here pertains to a restricted liquid line after the receiver. Provided is a service checklist. Assume that the refrigeration system is a TXV/receiver system, employing a filter drier and sight-glass. The system has R-134a as the working refrigerant.
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The Professor: Retrofit R-438A

November 2, 2009
There is an estimated 900 million pounds of HCFC-22 installed in refrigeration and air conditioning systems in the United States. This article covers one of the leading refrigerant blend candidates for retrofitting R-22 systems for both a/c and refrigeration applications.
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The Professor: Variable-Frequency Drives

October 5, 2009
The HVACR industry is one where both centrifugal pumps and fans are used on an ongoing basis. Because of this, HVACR systems are huge energy consumers. Creating higher-efficiency systems offers a tremendous opportunity for great electrical and monetary savings. Many of these savings can be achieved through the use of variable-frequency drives.
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The Professor: Retrofitting R-22 Systems

September 7, 2009
As mentioned earlier, most new systems will be manufactured with R-410A. However, the question of what is the best retrofit refrigerant blend for existing R-22 systems is often asked by technicians and equipment owners. There is no one quick-fix solution or answer to this question. The answer depends on several key factors.
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