Refrigerater and Ac Repairing

DESIGN FOR AIR CONDITIONING SYSTEM System design determines the basic characteristics. After an air conditioning system is constructed according to the design, it is difficult and expensive to change the design concept. Engineering Responsibilities The normal procedure in a design-bid project includes the following steps and requirements:  1. Initiation of a construction project by owner or developer  2. Selection of design team  3. Setting of the design criteria and indoor environmental parameters  4. Selection of conceptual alternatives for systems and subsystems; preparation of schematic layouts of HVAC&R  5. Preparation of contract documents, working drawings, specifications, materials and construction methods, commissioning guidelines  6. Competitive bidding by contractors  7. Evaluation of bids; negotiations and modification of contract documents 8. Advice on awarding of contract  9. Review of shop drawings an...

AIR CONDITIONING PROJECT DEVELOPMENT Basic Steps in Development The basic steps in the development and use of a large air conditioning system are the design, construction, commissioning, operation, energy efficiency upgrading, and maintenance. Figure 1.4 is a diagram which outlines the relationship between these steps and the parties involved. The owner sets the criteria and the requirements. Design professionals in mechanical engineering consulting firms design the air conditioning system and prepare the design documents. Manufacturers supply the equipment, instruments, and materials. Contractors install and construct the air conditioning system. After construction, the air conditioning system is commissioned by a team, and then it is handed over to the operation and maintenance group of the property management for daily operation. Following a certain period of operation, an energy service company (ESCO) may often be required to upgrade the energy efficiency of the HVAC&...

DISTRIBUTION OF SYSTEMS USAGE  According to surveys conducted in 1995 by the Department of Energy/Energy Information Administration (DOE/EIA) of the United States, for a total floor space of 58,772 million ft2 (5462 million m2 ) in commercial buildings in 1995 and for a total of 96.6 million homes in 1993 (among these, 74.1 million homes were air conditioned), the floor space, in million square feet, and the number of homes using various types of air conditioning systems are as follows: Much of the floor space may be included in more than one air conditioning system. Given the possibility that the floor space may be counted repeatedly, the original data listed in the DOE/EIA publication were modified. The 8 percent of the space system includes part in central hydronic systems and part in unitary packaged systems. Among the air conditioned homes in 1993, the unitary packaged system is the predominate air conditioning system in U.S. homes. HISTORICAL DEVELOPMENT The his...

CENTRAL HYDRONIC AIR CONDITIONING SYSTEMS Central hydronic air conditioning systems are also called central air conditioning systems. In a central hydronic air conditioning system, air is cooled or heated by coils filled with chilled or hot water distributed from a central cooling or heating plant. It is mostly applied to large-area buildings with many zones of conditioned space or to separate buildings. Water has a far greater heat capacity than air. The following is a comparison of these two media for carrying heat energy at 68°F (20°C): The heat capacity per cubic foot (meter) of water is 3466 times greater than that of air. Transporting heating and cooling energy from a central plant to remote air-handling units in fan rooms is far more efficient using water than conditioned air in a large air conditioning project. However, an additional water system lowers the evaporating temperature of the refrigerating system and makes a small- or medium-size project more complicated and...

AIR CONDITIONING Air conditioning is a combined process that performs many functions simultaneously. It conditions the air, transports it, and introduces it to the conditioned space. It provides heating and cooling from its central plant or rooftop units. It also controls and maintains the temperature, humidity, air movement, air cleanliness, sound level, and pressure differential in a space within predetermined limits for the comfort and health of the occupants of the conditioned space or for the purpose of product processing. The term HVAC&R is an abbreviation of heating, ventilating, air conditioning, and refrigerating. The combination of processes in this commonly adopted term is equivalent to the current definition of air conditioning. Because all these individual component processes were developed prior to the more complete concept of air conditioning, the term HVAC&R is often used by the industry.  COMFORT AND PROCESSING AIR CONDITIONING SYSTEMS Air Condit...