Refrigerator Troubleshooting Diagram

Archive for the ‘Compressors’ tag

Refrigerator Compressors

without comments

Air conditioning systems that are designed for residential and light commercial use are divided into three sections. Within each section there are many components. The main components are the condensing unit, the evaporator unit, and the thermostat. In some geographic areas, some of the names might be slightly different. For instance, some might call the evaporator unit the air handler. Both are correct.

Condensing units are installed wherever the builder thinks it will be cost effective. Because some of you might live in a house, some a condominium, some a duplex, we have written this book for all installation areas. Those of you that can point to your condensing units are lucky. Many owners don’t even know where their condensing unit is located. On a service call, you might spend some time trying to locate the customer’s unit. It might be under the parking area. Sometimes it is placed on the roof in clusters with other units. This gives you an idea that in certain areas, there might be a little time consumed in finding the condensing unit. When you find it and it is located in a unique place, make a notation on the evaporator unit or entrance panel where the unit is located.

Condensers can transfer heat using air or water as a transfer medium. Air-cooled condensing units are usually located in the outdoor air to be efficient. Water-cooled units are different. The heat transfer medium can be piped to the unit regardless where it is. A package unit is a unit that has only one section. The condensing unit, evaporator and sometimes the thermostat are located within a single cabinet. I tell you this to save you the embarrassment of looking for an air-cooled condenser on a water-cooled unit.

Before you open the cabinet of the condensing unit, turn off the electrical power supply to it. Always remove the panel slowly for many reasons. You might come face to face with an animal or a pressure refrigerant line about to burst. With the panel removed, you can look inside and begin to identify some of the component parts that make the condensing unit operate.

Written by sam

December 23rd, 2010 at 12:59 pm

Posted in Refrigerator Compressor

Tagged with

Refrigerating Compressors

without comments

In a refrigeration cycle, the compressor has two main functions within the refrigeration cycle. One function is to pump the refrigerant vapor from the evaporator so that the desired temperature and pressure can be maintained in the evaporator. The second function is to increase the pressure of the refrigerant vapor through the process of compression, and simultaneously increase the temperature of the refrigerant vapor. By this change in pressure the superheated refrigerant flows through the system.

Refrigerant compressors, which are known as the heart of the vapor-compression refrigeration systems, can be divided into two main categories:

• displacement compressors, and
• dynamic compressors.

Note that both displacement and dynamic compressors can be hermetic, semihermetic, or open types.

The compressor both pumps refrigerant round the circuit and produces the required substantial increase in the pressure of the refrigerant. The refrigerant chosen and the operating temperature range needed for heat pumping generally lead to a need for a compressor to provide a high pressure difference for moderate flow rates, and this is most often met by a positive displacement compressor using a reciprocating piston. Other types of positive displacement compressor use rotating vanes or cylinders or intermeshing screws to move the refrigerant. In some larger applications, centrifugal or turbine compressors are used, which are not positive displacement machines but accelerate the refrigerant vapour as it passes through the compressor housing. These various compressor types are illustrated in Figure 3.2.

Compressor types (Heap, 1979).

Compressor types (Heap, 1979).

In the market, there are many different types of compressor available, in terms of both enclosure type and compression system. Here are some options for evaluating the most common types (DETR, 1999):

• Reciprocating compressors are positive displacement machines, available for every application. The efficiency of the valve systems has been improved significantly on many larger models. Capacity control is usually by cylinder unloading (a method which reduces the power consumption almost in line with the capacity).

• Scroll compressors are rotary positive displacement machines with a constant volume ratio. They have good efficiencies for air conditioning and high temperature refrigeration applications. They are only available for commercial applications and do not usually have in-built capacity control.

• Screw compressors are available in large commercial and industrial sizes and are generally fixed volume ratio machines. Selection of a compressor with the incorrect volume ratio can result in a significant reduction in efficiency. Part load operation is achieved by a slide valve or lift valve unloading. Both types give a greater reduction in efficiency on part load than the reciprocating capacity control systems.

Written by sam

November 18th, 2009 at 5:24 am