Factory-built self-contained systems are very familiar in the form of domestic appliances, and retail units such as vending machines, drinking water chillers, and display cabinets and counters. Although larger systems may need to be finally assembled in situ, groups of components can be conveniently delivered as pre-assembled units, and it is the exception for a system to be custom built from individual components, except in the case of large industrial installations.
The main benefit of packaging is reduction in cost because a high proportion of the total cost of a refrigeration or air-conditioning system is made up of work which can be carried more quickly, efficiently and under better control within a factory rather than on the installation site. There are other advantages as well including:
1. correct selection and balance of components
2. factory control of system cleanliness, leak tightness, and in some cases, charging
3. inspection and testing of the complete unit before it leaves the factory
4. delivery to the site complete and in working order, so avoiding site delays for materials
5. fimplified site installation, with a minimum of disruption, inconvenience and cost.
A possible disadvantage is that the size range of available packages may be limited, but bespoke packages are frequently possible. There is a risk of misapplication, and care should be taken to understand the functionality of the package and its limitations. Comprehensive application data is normally available for all marketed packaged units to allow designers or sales engineers to make the correct selections for their purposes. Errors in application stem mainly from a lack of understanding of the requirement and a tendency to purchase at the lowest price without the protection of a clear specification. Once the application is fully understood, assessed, and specified the possibility of error is reduced.
Transport applications use specialized systems, and these are covered in Chapter 17, as are refrigerated display cabinets. Heat pump units are in 168 Chapter 27.
Posted in Refrigeration and Air Conditioning