Document pmzKoGZXanBEjy061xXdpxb2B

634 ___________ CHAPTER 36____________ 1946 Guide , 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 40 and 41. 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. This same , analysis should be extended to include a comparison of remote units with self-contained units. Self-contained units are possible where short term 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 Fig. 7. Remote Floor Type Room Unit Air Conditioner the other hand, remote type room units contain less mechanical ma' 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 room application: The criterion of a well controlled, installation is one which has neither too few nor too many controls. (See Chapter 34.) With the expansion of cities during the past decade, the problem of water supply has become a costly and ever present problem6. Con sequently, laws are appearing designed to restrict the usage of water wherever possible, particularly when substitute means tire available. . Evaporative condensers Eind cooling towers (described in Chapters 37 and 39) are means devised to save large quantities of water in: this connection.' , ,Unit Air Conditioners Unit Air Coolers Attic Fans 63S Tablb`1.: Standard Rating, Basis for. Self-Contained Air Conditioning Units Functions Types of Units Item Rating Condition Description, Value All Cooling All a Water-Cooled, Air-Cooled and. Evaporatively Cooled Condensers b c Water-Cooled d e Barometric Pressure ' 29.92 in. Hg. Unit Ambient and Air Entering Room--Air Inlet (1) Dry-Bulb (2) Wet-Bulb - 80 F 67 F Ventilation Air See Note Water Temperature Entering Unit 75 F Water Temperature Leaving Unit 95 F Air-Cooled f Air Entering Outside Air Inlet and Evapora- (1) Dry-Bulb tively Cooled (2) Wet-Bulb Condensers 95 F 75 F Heating g All Types Provided with Heating Function - - h Unit Ambient and Total Air Enter ing Unit 70 F Heating Medium, Pressure or Temperature (1) Dry Saturated Steam (2) Water In (3) Water Out 16.7 lb per sq in. abs. 180 F 160 F All Types i Unit Ambient 70 F Humidifying Humidifying Function Total Air Entering Unit(1) Dry-Bulb (2) Wet-Bulb 70 F 53 F Air ' Circulation ah k Filters New and Clean Note: Rating shall be based on both ventilation and recirculated room air entering at 80 F dry-bulb nd 67 F wet-bulb temperature. (The Note as given in the code has been condensed in order to remove material not pertinent to this chapter). ^ Most manufacturers furnish equipment designed for use in combination with these water savers. - Municipal plumbing, heating, electrical and refrigeration codes, as well as fire underwriter restrictions, are likewise having their effects on the application of unit, air conditioners. Meeting municipal and national code requirements should be an important item in connection with the installation of tmy unit equipment. Ratings There are two codes governing the rating and testing of unit air con-, ditioners. The .first code, Standard Method of Rating-and Testing Air Conditioning Equipment \ covers all types of air conditioning units except the self-contained type. The latter is covered by the second, code, The, Standard Method of Rating and Testing Self-Contained Air Conditioning Units for Comfort Cooling *. The two codes Eire necessary because of the basic difference caused by the heat given,up by the self-contained, units.