Dave Demma

Dave Demma is Supermarket sales manager, Refrigeration & Air Conditioning - Climate & Industrial Controls Division, Parker Hannifin Corp. He can be reached at dgdemma@parker.com.


The Electric Suction Line Regulator

By Dave Demma
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In the electric suction line regulator, the step motor assembly is connected to the main modulating piston through a gear reduction drive. As the motor rotates in one direction or the other, it will drive the main piston open or closed. These valves are commonly referred to as electric EPR, EEPR, or electric evaporator pressure regulator valves.
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The Untypical Refrigeration System

By Dave Demma
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For the last five years, the supermarket industry has undergone a gradual shift in thinking regarding the preferred method for controlling evaporator discharge air temperature. You might call it an untypical … and more modern approach.
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Heat Reclaim Service Issues

By Dave Demma
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This is the final in a three-part series that began in the March 12 issue with a discussion of heat reclaim in three-way valve operation and continued with heat reclaim in series and parallel in the March 26 issue.
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Heat Reclaim in Series and Parallel

By Dave Demma
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Heat reclaim can be accomplished with either a series or parallel method. In the series approach, when a finned tube heat exchanger is used it is properly termed a heat reclaim coil.
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Heat Reclaim with Three-Way Valves

By Dave Demma
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If the goal of the vapor-compression cycle is to convert the refrigerant to the state necessary to be a useful heat transfer medium (the evaporation stage), the other three stages can be looked upon as a means to an end. However, they perform no useful function other than preparing the refrigerant in its journey of transformation into something useful. Or do they?
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