Articles by John Tomczyk

The Professor: ‘Wye’ or ‘Star’ Configurations

A Look at Electrical Service Transformers

John Tomczyk discusses the Wye or Star configuration of the three-phase electrical service, which usually delivers four wires to the building.


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The Professor: Low Ambient Controls Reduce Head Pressure

Control Is a Style of Head-Pressure Control Valve

When refrigeration systems are exposed to low-ambient conditions, the condensing pressure (head pressure) will fall. If the head pressure gets too low, the metering device will not have enough pressure drop across it to operate properly.


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The Professor: TXV Dos and Don’ts

The Externally Equalized Thermostatic Expansion Valve

The thermostatic expansion valve (TXV or TEV) is a metering device located between the liquid line and the evaporator. 


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The Professor: Refrigerant Undercharge

Dealing With R-134a Shortfall in a System

John Tomczyk, Professor of HVACR at Ferris State University and co-author of Refrigeration and Air Conditioning Technology, discusses refrigerant undercharge.


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The Professor: Diagnosing Bad HVAC Compressor Valves

When Low Head and High Suction Pressures Collide
Many service technicians experience service calls where the compressor has both a low head pressure and a high suction pressure. Often, the refrigeration equipment is still running, but the product temperature is suffering about 7-10°F.


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The Professor: An Overcharge of Refrigerant

Knowing Symptoms Can Lead to Solutions
It is the system check sheet that will tell the service technician whether a system is overcharged or not. Service technicians must install pressure gauges and thermistors — or some other sort of temperature-sensing devices — in order to systematically troubleshoot a refrigeration system correctly.


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The Professor: Flooding and Slugging of Compressors

Understanding the Terms Critical to Troubleshooting

Clear, concise, and accurate communication between service technicians, parts suppliers, customers, and the home shop is rapidly gaining importance as the HVACR field transitions and becomes more technically oriented.


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The Professor: Recognizing, Solving Refrigerant Migration

Eliminating Refrigerant from the Compressor’s Suction Line or Crankcase

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: Leak Checking a Water-Cooled Condenser

Locating Refrigeration Cycle Leaks May Be Easier Than You Think

When a refrigeration system has lost most of its refrigerant charge in a short period of time, the leak is probably significant and should be easy to find.


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The Professor: Three-Phase Motor Voltage Unbalance

Troubleshooting an Overheating Compressor

Compressor overheating is usually caused from high compression ratios. High compression ratios can be caused from a combination of high condensing pressures (temperatures) and low suction (evaporating) pressures.


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Matt Barga, portfolio manager — a/c and coils, Ingersoll Rand, discusses how the company is working to comply with the new energy conservation standards for heat pumps and air conditioners that go into effect on Jan. 1, 2015. Posted on Dec. 19.

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