Document Kzbv5jaOezRwgM9K8qDGJq7vo

914 L| CHAPTER 61 * 1965'Guide 'And- Data iBook' thermal overload relay on the magnetic'contactor) the ther mal overload relays of auxiliary.' equipment such as pump motor and tower fan motor, and electrical interlocks of th chilled water pump magnetic contactor and holding coil of the compressor magnetic contactor. On those units where a singly pump-out of the compressor is desired, a non-recycling relay is employed to eliminate nuisance cycling when the system is Testing and Rating^. ; Unitary water chillers should be tested in accordance with' ASHRAE "Standard'30-60,. Methods iff'Testing for' Rating' Liquid Chilling Packages,- which outlines the tost methods,' inktnimerits:required, and toe test'procedure. Ratings should* be obtained in accordance'with ARI Standard 590--62/ Reciprocating Water-Chilling Packages PART II: DRINKING WATER COOLERS" Fig. 6 .... Typical Control Schematic Pockaged A mechanically refrigerated drinking water cooler, consists Water Chiller of a factory made assembly,'in one structure, that employs' a complete, mechanical, refrigeration system -and which has the' rHigh-pressure cutout twitch. This switch functions to stop the ation of the system when excessive pressures are reached on High side. Many units are supplied-with high-tide switches, primary function.of cooling potable watcr,and-provides for` dispensing such'water by either.integral'or remote mesas,sorj both.-' , _/ ` - with lock-outs that require manual reset after determination of .Water, copiers differ,:from water chillers in that, water the cause of the interruption. coolers are used to dispense potable water, whereas water Freeze control. This type of control is normally furnished to stop the system when the conditions are such that freezing of the Quid to be cooled is imminent. In some systems this is,a direct--; acting temperature control set at the cutout temperature. chillers are' used in air-conditioning systems for residential, commercial, and industrial applications, as well as cooling water for industrial processes. On others a low-tide pressure switch used is preset to stop the The capacity'of a water, cooler is expressed in gallons' per machine after operating for an interval of tune at this preset pressure. , * ' Oil safety twitches.'Most larger systems include ah oil pressure differential switch to assure a positive oil pressure above the back1 pressure of the system. The oil safety switch will interrupt thei hour and is the quantity of'water 'cooled. in one hour under the:conditions shown in the"'paragraph, entitled, Ratings.- Normal'standard capacities of water coolers,range from 1 to) 30 gphl ' t ' t>._;''/);) operation.of the system on low oil pressure and normally will: require manual resetting of the device after determination of ,the, : TYPES ' .:=/ cause. '' '' Crankcase heaters. Many systems utilize the crankcase, heater ( , The three basic types of water coolers are'showri in Fig) 7. as a means to boil off entrained liquid refrigerant in the crankcase' 1. ' Bottle Type'. A bottle water cooler ia one which employs a and maintain a temperature within the oil supply during the off- bottle or reservoir for storing the supply of water to be cooled cycle to assure a refngerant-free oil source. and utilizes a faucet or similar means for filling glasses or cups or Relief valoe. The high tide of the system is always protected by other containers and which includes a waste water receptacle. a pressure relief'device set to start functioning at a pressure not to exceed the design working pressure of'the pressure'vessel.'' 2. Pressure Type. A pressure-type water cooler is supplied with potable water under pressure and includes a waste water re The discharge capacity of the relief device is determined!in ac-. ceptacle or means for disposing of water to a plumbing drainage cordance with the American Standard. ASA B9.1---1964, Safety: Codefor Mechanical Refrigeration. system (see Ftg.L8).! Prrasure^type^water,coolers can utilize a faucet or similar means for filling glasses or cups, or may employ a valve to control the flow of Water as a projected stream from a bubbler so.that water' may.be consumed without utilizing The control systems, of unitary water chillers vary some-" glasses or cups.: what but the following sequence is usually- followed (Fig. 6):' A manual switch is provided for starting and stopping the- machine regardless of the settings of the various control- switches. ' - ' When the switch is in the off position, the unit is inopera-: live, but the crankcase heater is energized. When the switch is in the on position, a circuit should exist' through various components to allow ;the.unit to start. In where a pump-down cycle exists, ckising of the on-o#- switch-will complete, a circuit through the temperature-con-, troller and the refrigerant feed solenoid. When the tempera-,, tore control is closed, indicating that cooling is,required,,the Iiquidrfeed solenoid opens and refrigerant is admitted into)the- low side of the system. This action allows toe pressure to feuild up within toe low side of the-system so that-the low- pressure cutout switch may dose to start the machine. The low-pressure cutout switch is. a part of' ^circuit, ihchiding. the high pressure cutout switch, the oil safety,switch,,the, Fig. 7 v.. . .Bask .Types,of Drinking'.Water'.Coolers j;- WaterChillersandCoolers, i 915 condenseiB.are.sometimes included. .Water-cooled condensers of tube-on-tube construction are used on.models intended for high ambient temperatures or where lint and dust in the air make air-cooled types unpractical. - Refrigerant Control Capillary tubes are.used almost exclusively for refrigerant flow control in hermetically .sealed systems. In belt-driven systems and some hermetically sealed * systems expansion valves are used. 3." Self-Contained Remote" Type.- A seif-contained remote1 type' cooler is a factory assembly'in one' structure which employs a> onmplflta: mechanical. refrigeration system and .which-has-the primary .function of.cooling potable water for.;delivery--to -a separately installed dispensing means. ... ' Coolers, in addition to the baric type descriptions, are,also described as air-cooled or wateNcopled, and by any specialized use or additional functions they perform. 1. Specialized Uses: Explosion Proof. An explosion-proof type water'cooler is one which is constructed for safe operation in hazardous locations as rlmwifiwH in Article 500 of the^Aarionoi Electrical Code. - 6. Cafeteria Coofm.;-A,cafeteria,tvpe-.cooler-is one whichis supplied with water under pressure from a piped system and'is intended primarily for usa-m cafeterias and <restaurants for dis pensing water rapidly and conveniently into glasses or pitchers. It includes a means for disposing of waste water to a plumbing drain system.' ` 1 2. Additional Functions: ) ... . - .... - a.'- Refrigerated Compartment. A'-water cooler may elan have a refrigerated compartment with or without provisions for moving ke. , .,j ...... . :/ ' 'b. 'Hot IVoter. A water cooler may'also include a means for heat ing and dispensing potable water for .making instant hot bever ages, soups, etc. r. .-i 3. type of Installation (see Fig, 9); . a. Free standing. . r' b. Flush to walL ' WaD bung.' "", REFRIGERATION SYSTEMS Compressors Hermetically sealed compressors are commonly used for a-c applications, both 50 and 60 cycle. Belt-driven compres sors are generally used only for d-c and 25-cycle supply. Compressors are similar to those used in refrigerators aM range from */u to H hp. Condensers Fan-cooled condensers are most commonly used. In coolers rated less than 10 gph, natural-convection-cooled (static) Evaporators /,).)'' Most water coolers manufactured today have-the evapora tor formed by refrigerant tubing bonded to toe outside of a water circuit. The water circuit is usually si *nny or a coil of large tubing. Materials used in the water circuit are usually non-ferrous or stainless steel. Since the coolers dispense water for human consumption sanitary requirements must be kept in mind Precoolers Pressure-type coolers are often equipped with precoolers to exchange heat from the supply water to the waste water. When drinking from a bubbler stream the.user wastes ap-' proximateiy 60 percent of the cold water down the drain. A precooler is an arrangement for putting the incoming water in heat exchange relationship with the waste water. Some times the cold waste water is also used to subcool liquid refrigerant. Coolers intended only to dispense water into cups are not equipped with precoolers since there is no appreciable quantity of waste water. Multiple Temperature Systems Water coolers that also provide a refrigerated storage space,' commonly referred to as Compartment Coolers, have the same control compromises common to all refrigeration devices'that attempt- two-temperature refrigeration using a ningla com pressor. ".................... - r Most bottle-type compartment coolers are provided with toe simplest series system in which the refrigerant feeds' first to a water-cooling coil and then through a restrictor device to Toble 1 .... Standard Rating Conditions* Type of Cooler Bottle Types Pressure Types Utilizing Precooler Wobbler Service) Not Utilizing Precooler Compartment-Type Coolers rempemfwre, F Heated Split, Met Coded Potable percent Ambient Wo**r Water Water* 90 90 50 165 None 90 80 50 165 60 90 80 50 165 None During the Standard Capacity Test, there shall be no molting of ice in the refrigerated compart ment, nor shall the average tem perature exceed 46 F. NOTE: For water-cooled eondenaer woUr coaler* the estabfiahed flow of water through tba onnriritwii ahaU apt rafted 3X tine* tha Baae Rato Capacity and the outlet condenser water temperature shall sot exceed 130 F. Bate Rate Capacity ei a preeeuie water oooW having a preoodler In tha Quantity of water eooted m one hour, eayteejeil in per hour, at the Standard Bating Condition*, with 100 percent direnion of cpill from the preoookr. This temperature shall be referred to ** the Standard Satins Temperature (Heating). * Reprinted by pernriarion from *Ri Standard 1010-02. J J. I ifc