Articles by John Tomczyk

The Professor: Oil Pumps and Net Oil Pressure

Understanding the Differences is Key for Successful Servicing
June 30, 2014

Often, compressors in the refrigeration and air conditioning fields have forced oiling systems. Here is a look at some of those oil pumps.


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The Professor: Don’t Forget About the Oil Check Valve

Dealing With Startup and System Problems
June 2, 2014

An overview of the oil check valve, which will only let oil pass from the compressor’s motor barrel to its crankcase.


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The Professor: Troubleshooting Using Compressor Discharge Temp

Checking Over an Often Overlooked Aspect of Servicing
May 5, 2014

The compressor’s discharge line temperature is important because it is an indication of the amount of heat absorbed in the evaporator and suction line and any heat of compression generated by the compression process.


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The Professor: Crankcase Heaters

Coping With Refrigerant Migration
March 31, 2014

Migration of refrigerant to the compressor’s crankcase during an off cycle is a serious problem, as significant compressor damage can occur if the problem is not remedied. 


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The Professor: Understanding, Avoiding Transformer Burnouts

Solving Low-Voltage Power-Consuming Faults
March 3, 2014

This column will try to explain the voltages associated with the high or wild leg coming from the secondary of a Delta service transformer. 


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The Professor: ‘Wye’ or ‘Star’ Configurations

A Look at Electrical Service Transformers
February 3, 2014

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
January 6, 2014

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
December 2, 2013

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
November 4, 2013

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
October 7, 2013
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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Twin Cities contractor Aabott Ferraro helped retrofit an older St. Paul home.

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NEWSMakers: Doug Dougherty

Doug Dougherty, president and CEO of the Geothermal Exchange Organization (GEO) joins the program to discuss the latest happenings with GEO, including the drive to get included in state and federal definitions of renewable energy, plus the future of geothermal.  Posted on July 25.

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