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222 CHAPTER 15 1959 Guide heater should therefore be obtained from the manufacturer and should be kept at the unit. Fan bearings and drives must be given the lubrication and other attention specified by the manufacturer. If the unit is direct-connected, the couplings should be inspected pe riodically for wear and alignment. V-beit drives should have all belts replaced with a matched set if one belt shows wear. Periodical inspections of traps, check valves, and air valves, and the replacement of worn parts are important maintenance items. Strainers should.be cleaned regularly. When filters are incorporated in the unit, they must be cleaned or replaced when dirty. For prevention of corrosion in unit heaters, see Chapter 55, Corrosion and Water Formed Deposits, .Causes and Pre vention, in this edition, and also Bulletin 12, The Care and Maintenance of Steam and Hot Water Unit Heaters, pub lished by the Air Moving and Conditioning Association, Inc. REFERENCES 1ASHVE Standard Code for Testing and Eating Steam Unit Ventilators (ASHVE Transactions, Vol. 38, 1932, p. 25). *G. L. Larson, D. W. Nelson, and R. W. Kubasta: ASHVE Research Repost No. 938--Investigation of air outlets in class room ventilation (ASHVE Transactions, VoI. 38, 1932, p. 463). F. C. Houghten, Carl Gutberlet, and M.- F. Lichtenfels: ASHVE Research Report No. 1017--Air supply to classrooms in relation to vent flue openings (ASHVE Transactions, VoL 41, 1935, p. 279). * Standard Code for Testing and Rating Steam Unit Heaters (Adopted jointly by The American Society or Heating and Ventilating Engineers and Industrial Unit Heater Association, 1UHA Bulletin No. 10, January 1950, 2nd ed.). * Standard Code for Testing and Rating Hot Water Unit Heaters (Adopted jointly by The American Society op Heat ing and Ventilating Engineers and Industrial Unit Heater As sociation, IUHA Bulletin No. 11, April 1953, 2nd ed.). *G. L. Larson, D. W. Nelson, and 0. C. Cromer: ASHVE Research Report No. 958--Temperature gradient observations in a large heated space (ASHVE Transactions, Vol. 39, 1933, p. 243). G. L. Larson, D. W. Nelson, and John James: ASHVE Research Report No. 1011--Tests of three heating systems in an industrial type of building (ASHVE Transactions, Vol. 41, 1935, p. 185). Piping, Trapping and Venting Steam and Hot Water Unit Heaters (Air Moving and Conditioning Association, Inc., Bulle tin No. 15). CHAPTER 16 UNITARY AIR-CONDITIONING EQUIPMENT Definitions, Classification, and Components of Unrf-fype Equipment, Remote and Self-contained Units, Room Air Conditioners, Ratings of Unit Air Conditioners, Application of Unitary Equipment, Unit Air Coolers HIS chapter presents the physical characteristics of To obtain the economies of factory production, component Tair-conditioning and air-cooling units; a suggested pro assemblies are available in the size ranges of greatest usage. cedure for selection of units; and some of the factors inIn addition to assemblies of high-side equipment in con volved in the application.of unitary equipment. In general, densing units, the fan-coil units are factory made in various factory-produced unit equipment can be obtained to accom types as indicated by the preceding definitions. plish all of the functions possible from field assemblies, but the If the condensing unit and the cooling and heating coil advantages of unit equipment are most apparent in small surfaces are carefully selected, and if proper consideration is and moderate capacities. Above 12,000 cfm capacity, or ap given to reduction of piping losses, the performance of the proximately 40 tons of refrigeration capacity, handling and combined system will compare favorably with field assembled assembly costs generally favor the use of field-assembled apparatus. A system tn which the air handling unit is units. Multiple application of unitary equipment is fre separated from the condensing unit, is called a remote sys quently justified for large gross tonnage installations where tem. The conditioning unit is designated as a remote unit. zoning or a minimum amount of ducts is desirable. Capacities of remote units usually range from 2 to 100 tons. The self-contained air-conditioning or cooling units are DEFINITIONS widely used in capacities through 15 tons, and are available The term air-conditioning unit has been loosely used as a name for all types of factory produced air-handling, cooling, or heating units. A joint committee1, * * on Rating Refriger ating Equipment has defined the various types of unitary equipment as follows: 1. A Cooling Unit is a specific air-treating combination con sisting of means for air circulation and cooling within prescribed temperature limits.' 2. An Air-Conditioning Unit is a specific air-treating combi nation consisting of means for ventilation, air circulation, air in larger sizes. Each model is designed for a specific cooling capacity and range of air delivery. Experience has demon strated that well designed and properly applied equipment of this type produces excellent results in commercial comfort installations. In most designs of the larger self-contained units, the equipment can be adjusted to approximate the load calculations through a selection of the air quantity. An increase of air quantity in this type of equipment increases the sensible heat proportion, and a decrease of air quantity tends to provide a lower leaving dew point and a high pro cleaning, and heat transfer, with control means for maintaining temperature and humidity within prescribed limits.1 3. A Cooling Air-Conditioning Unit is a specific air-treating combination consisting of means for ventilation, air circula tion, air cleaning, and heat transfer, with control means for cooling and maintaining temperature and humidity within prescribed limits.1 portion of moisture removal. However, the usual field prac tice is to adjust the fan speed for quietness and air distribu tion rather than for ratio of latent to sensible loads as indicated by a load estimate. To meet the requirements of individual comfort in small rooms and offices, self-contained units, called room coolers, 4. A Self-Contained Air-Conditioning or Cooling Unit is one in which a condensing unit is combined in the same cabinet with ' the other functional elements. Self-contained air-conditioning units are classified* according to the method of rejecting condenser heat (water-cooled, air-cooled, and evaporatively cooled), method of introducing ventilation air (no ventilation, ventilation by drawing air from outdoors, ventilation by exhausting room air to the outdoors, or ventila tion by a combination of the last two methods), and method of discharging air to the room (free delivery or pressure-type). find extensive and economical application. These units are usually restricted to summer and intermediate season op eration, and range from to 1 Vt tons of refrigeration capacity. A special application of remote units is found in the unit air cooler which is used extensively in refrigeration work. Its primary function is to reduce temperatures in insulated and sealed storage spaces, and humidity control is a sec 5. A Free Delivery Type Unit takes in air and discharges it directly to the space to be treated without external elements which impose air resistance.1 6. A Pressure-Type Unit is for use with one or more external elements which impose air resistance.1 7. A Forced-Circulation Air Cooler is a factory encased assembly of elements by which heat is transferred from air to refrigerants* ondary consideration. Because of the small temperature dif ferences between the coil and room temperatures, unit coolers handle three to five times as much air per ton as remote units used in air conditioning. The attic fan or exhaust fan is sometimes referred to as a cooling unit, but since it contains no element of heat trans fer, it is treated in Chapter 22, Fans. CLASSIFICATION OF UNIT-TYPE EQUIPMB^IT COMPONENTS OF UNIT-TYPE EQUIPMENT Field assembled apparatus as described in Chapter 19 can be designed in shape, size, and capacity for any application, with tlie refrigeration and heating system exactly balanced to a specific load condition. The unitary equipment is designed for the air-conditioning loads of most common occurrence. Highly special projects and projects of infrequent occurrence may require fieldassembled equipment for best results. Field modifications 223