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HEATING VENTILATING AIR CONDITIONING CUIDE 1944 to achieve the desired conditions. A typical remote floor type room unit air conditioner is shown in Fig. 7. Application , , In the application of unit air conditioners it is important to consider several factors: : 1. Location of equipment. 2. Air distribution. 3. Multiple units versus central station system. 4. Multiple rembte unit system versus a self-contained unit system. 5. Methods of control. 6. Methods of conserving water. 7. Code limitations. In choosing locations for air conditioning units, consideration must be given to the characteristics and use of the conditioned space; type of system contemplated; duct locations; sources of power, water, refrigera tion, heating and drainage; and accessibility of equipment and system for maintenance. Where units are placed within the conditioned area, particular atten tion must be given to air distribution, sources of outside air and con venience to service sources and facilities previously noted. Skill and ingenuity are required to produce a neat appearing, inconspicuous job without sacrificing quality from an engineering point of view. Furring in of duct work, and building in and refinishing to match existing furniture and fixtures are ways this may be accomplished. Where location of equipment outside of conditioned space is possible, use may be made of storage rooms, halls, basements or any space less valuable than that to be conditioned. Less emphasis need be placed on the appearance of equip ment. However, choices of equipment location are frequently influenced by such economic factors as long runs of insulated ductsjn order to locate units near refrigeration sources, versus short duct runs butlong extensions of service facilities. Care must be taken that equipment will not be damaged by climatic conditions. Air distribution from units located within the conditioned area is by means of grilles, either fixed or adjustable and mounted iii air distribution headers, either furnished with the unit or constructed at the installation to meet the needs of the application under consideration. A system of ducts and distribution grilles may also.be used, similar to the arrangement used when equipment is outside of the conditioned area. The problem'of securing a supply of outside air is often a difficult'one. The proper design of ducts is of major importance for good air distribution. Chapters 31 and 32 are devoted to these subjects. - In the analysis of any large structure to be air conditioned which is divided into small spaces, such as an office building or hotel, a comparison should be drawn between the use of units and a central plant system. This study is one of economics, and should include such factors as first cost, installation costs, obsolescence, depreciation, maintenance costs; return on investment, flexibility, time of installation and. possible loss of useful space during installation. . . .. 436 CHAPTER 23. UNIT AIR CONDITIONERS, UNIT AIR COOLERS, ATTIC FANS This same analysis should be extended to include, a comparison of remote urtits with self-contained units. Self-contained units are possible where short tertn leases are involved, or where wiring can readily.'be brought to location or where existing water and drain facilities are adequate to handle the increased demand of water-cooled models. On the other hand, remote type room units contain less mechanical ma- Fig/6. Suspended Propeller Fan Type Unit Air Conditioner chinery, avoid the operating cost penalty of an air-cooled condenser, as in the case'of the self-contained, air-cooled room units, and seldom require heavy wiring to handle the fan load. In general, the smaller remote units are more suitable for use with new construction, where the units will probably remain during their useful life. This condition may change where larger, ceiling mounted units are compared with the floor mounted self-contained units. Controls are essential in unit application and range from the simple snap switch of a room unit to elaborate means of.-control ling temperature, humidity and air movement in laboratory and' testing 437