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?!0 CHAPTER 60 normal operation hut sufficient power must he available for the.initial pull-down of a warm-cabinet or.overloading due to excessive {reeling loads. Hie selection of compressor lubri cating oil involves the consideration of wax precipitation at the lpw temperatures. Special mis which will meet this require ment should be used. Permanent dehydrators, in addition -to thorough faetory.dehydration, are frequently included in the refrigerant circuit, because the moisture limit in thpgp low temperature systems is-extremely low. Condenser design has followed closely the household re frigerator practice in both static and forced-draft types with some manufacturers using all or a portion of the cabinet shell as a plate oondenser. As in compressor motor -design the normal condenser load will be relatively, small, but adequate .capacity for peak loads must be provided. . Refrigerant 12 and Refrigerant 22 are used exclusively in this application. Refrigerant 22 has gained wide acceptance because the increase in refrigerating effect of this refrigerant over Refrigerant 12 for the same displacement compressor offers economic possibilities by using an available mass pro duced compressor to operate a larger freezer dr to operate a freezer in place of a refrigerator. . Temperature controls for operating the refrigerating unit of household freezers are standard devices designed to operate at the required temperatures. The location of the temperature sensitive element requires careful consideration. A constant temperature of tire stored load is highly desirable from the standpoint of preserving quality products for long periods of storage. Temperature variations due to cycling of the re frigerating unit as well as those due to changes in temperature should be held to a minimum. If possible, the temperature control should automatically call for continuous operation of the refrigerating unit until fresh bads of food are frozen. STORAGE AND FREEZING TEMPERATURES . Extensive research in the field of the quality of frozen foods versus storage time and temperature him established a .tem perature of 0. F as satisfactory for most foods for a storage period of six montits to a year. Certain foods, particularly pork and its products, require either lower temperatures or shorter storage periods. The effect of the rate, of freezing on the quality- of .frozen foods has been extensively investigated. Early-authorities have, perhaps, overdressed the necessity of quick freezing. A summary of the literature leads to the conclusion that high quality can be achieved with relatively slow freezing, provided that recommendations- regarding the other, factors in thiq process of food preservation are carefully followed. Jn the de sign of the household sizes of freezers, provisions should be made for the freezing of limited quantities of food in propor tion to the size of the freezer, and specific instructions. shonM be available to the user as to the proper placement of food to be-frozen and the m*imnm quantity that may be frozen:in 24 hours without seriously disturbing.the .stored load ternperature. The maximum rise in storage temperature has been considered as 5 F deg. On the assumption that instructions are followed, the provirion of such freezing facilities will insure the ......... 1965 Guide And Data ..Book rapid cooling of the warm load to a point at which spoilage is avoided. Freezing by contact , with horizontal refrigerated platesur by rapidly moving air offers the best possibilities for quick freezing in the household freezer. Adequate condensing unit capacity will be required to carry the recommended freezing load in addition to the normal operating load.. REFRIGERATION FAILURE Since the financial loss through spoilage of the contenteofa freezer can be serious, the problem of refrigeration failure Has received considerable attention. The effects of ambient tem perature, quantity of stored load, door openings, and indi vidual cabinet heat leakage seriously affect any estimate of the time available between loss of refrigeration and the develop ment of spoilage temperatures. In general, thawing of at least part of the food may be expected within 30 hr, and tempera tures exceeding a safe limit of 50 F may occur in' 75 hr. The application of dry ice is recommended'as a temporary source of refrigeration. ' Early knowledge of the failure of refrigeration is of primary importance in avoiding food spoilage. A variety of warding devices and temperature indicators is available^ These devices are offered by many freezer manufacturers as standard equip ment or as an accessory. To obtain the muYitnnm protection the thermal element of such a device must be carefully lo cated with regard to temperature distribution within the freezer, .' -' TESTING AND RATING . The testing and rating of household freezers are covered by National Electrical Manufacturers Association Publication FH 1-1955 (ASA B38.3-1955, ASHRAE Standard 13), and are generally similar to those for refrigerators. BIBLIOGRAPHY C. F. Abang: Methods of automatically defrosting-household refrigeratore (Refrigerating Engineering, May 1952, p. 485). F. C. Wilson: Evacuated and, gas-filled insulation systems (Refrigerating Engineering, Apnl 1957, p. 57).' ` H; E. Webb: Noise problems in household refrigerators (Rbfrxgerahnq ENGINEERING, October 1949, p. 955). - W. R. Briakin: Moisture migration in hermetic refrigeration systems (Refrigerating Engineering, July 1955, p. 42). H. O. opauschus and R. S. Olsen: Gas analysis--a new tool for determining the chemical stability of hermetic' systems (Re frigerating Engineering, February 1959, p. 25); .. F. H, Fleischer: Motor design for hermetic units (Refrigerat ing Engineering, October 1951,p.963). A. P. White: Thermal protection of motors as related to non- eellulotic insulation (Refrigerating Engineebing. -February 1959,p.37).- -- R. F. Roider: Field testing.of household refrigerators (Re frigerating Engineebing, September 1949, p. 874). E. C. Tanner: The development of a home freezer (Refriger ating Engineebing, April 1946, p:321). C. E. Lund: Technical phases of home freezer development (Refrigerating,Engineering, June 1946, p. 513).' E. W.-Comings: What causes ice formation in food freezer insulation' (Refrigerating Engineering. February' 1948 o 156). ' ` - - - V. - L. M. S. Cooper:.Chest vs upright^--an engineering evaluation (Refrigerating Engineering, September 1953, p.,964): CHAPTER 61 WATER CHILLERS AND COOLERS UNITARY WATER CHILLERS: Selection Requirements, Design, Construction Standards, Compressors, Condensers, Coolers, Refrigerant Piping, Confrols, Testing one/ Rating; DRINKING WATER COOLERS: Types, Refrigeration Systems, ' Stream Regulators, Ratings, Standards and Codes THIS, chapter discusses unitary equipment for water r-hilllng (Part 1), and for cooling of drinking water (Part II). PART I: UNITARY WATER CHILLERS The unitary water chiller is a factory prefabricated as sembly (not necessarily shipped as one package) of one or more reciprocating. compressors, condensers, and water coolers, with electrical controls, interconnections, base and accessories. The water-cooled condenser is commonly included as an integral part of the unit, whereas the air-cooled and evapora tive'condensers are most frequently provided for remote in stallation. A unitary water chiller may be used to cool liquids other than water, but this chapter will discuss only applica tions involving the cooling of water. Unitary water chillers are used in air-conditioning"systems for residential, commercial, and industrial applications, as well as for cooling water in industrial processes. Chillers used in residential systems are generally of the sealed-system type with readily replaceable components. Units of this type are designed for economy with replaceable rather than repairable parte. Residential units are generally available with capacities ranging from 12,000 to 60,000 Btuh. For small commercial applications, chillers are available with capacities from 60,000 to over 180,000 Btuh. Many of these units are of the sealed, repairable type, using semihermetic compressors. Service valves, gage connections, arid accessories are provided for testing and checking. The smaller sizes of these units often are used in larger residential systems.' Chillers used for industrial and large commercial applica-' tions generally have capacities ranging from 180,000 to 3,000,000 Btuh. These units usually are provided with some mranq of capacity reduction. Reduced voltage starting equip ment may be furnished. SELECTION REQUIREMENTS Selection requirements to be considered include applica tion (air' conditioning' or process cooling), design temperature requirement, availability of power, space limitation, economic limitations, nd load variations. The selection of the unitary water chiller is a part of the design of an overall system since in most cases the chiller' is only a component of a complete system and does not perform the entire cooling function within itself. ' : Theeenerml roponaibility for this chapter to '[<' to TC 8.3, Drinking. Wcttr Cooler*, *oa TC 9.2, liquid Heat Exchanger*. The load to be imposed upon the water chiller is obtained by the cooling requirements and converting to gpm of water for a specific cooling range (see Chapter 43). The load is indirect in that it is obtained from other heat ex changers which are removing heat from the space or fluid to be cooled. The unit should therefore be selected to be able to handle the peak loads of the system and operate to balance the system at a condition favorable to the operation of all com ponents. The water bong cooled normally requires make-up water only in small quantities to replace that which is bled off in air vents throughout the water system. Because of this, and also becauy* the temperature of the cooled water does not tend to induce scaling, low scaling factors are used in determining the operation of the cooler. Common practice is to use a scaling factor of approximately 0.0005 for this fouling resistance. As a contrast, the water-cooled condenser has a fouling resistance which varies within greater limits to accommodate the various types of water normally used. The reader is referred to Part I, Water-Cooled Condensers, of Chapter 42 for information oh these values. A significant requirement of a unit is the ability to vary the capacity as required by changes in the load. These load fluctuations are normal and can be handled on most equip ment by the use of various capacity reducing means. A com mon method of capacity reduction is by means of internal or external unloaders on the compressor, responsive to the suction-pressure.or in some cases controlled by external tem-; peratures. This allows the unit to cycle from a fully loaded, condition to some condition near unloaded without stopping.-1 On units having two or more compressors, it is common to vary the capacity of the unit by starting and stopping one or more compressors in sequence. On those installations requiring year round operation or during seasons iriwhich the outside temperature falls below 80 F, the system should be designed to regulate the condens ing capacity to maintain sufficient high-side pressures. (See' Chapter 42.) : ' DESIGN The range of .sizes' available fox use generally .follows the motor horsepower sizes with nominal capacities of about 1 ton per horsepower in the' range from approximately 2 tons up to as high as 250 tons. The-arrangement of the unitary water chiller is generally dictated by the size of the individual, components, and.desirable weight distribution for noise isola tion and 'structural `economics.' Normally,' it is desirable to maintain the heavycompressor component in the lowest part 911