Water Cooled Modules OPERATION & MAINTENANCE - Multistack

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2.0 Theory of OperationThe Multistack chiller provides chilled water to an external load based off of thereturn water temperature to the Multistack master control. When the EnteringChilled Water sensor sends the signal to the master control that cooling is needed,compressors will begin to start and produce chilled water. The point at which theECHW temperature calls for compressors to start is determined by the Upsetpointand the Variable Set-point setting in the system variables menu of themaster control.When the ECHW sensor senses that the chilled water temperature has droppedbelow the set-point, compressors will begin to cycle off.3.0 Daily Log SheetOn the back page of this manual is a chiller information log sheet. The log sheetcan be used daily, weekly or as desired to record operation characteristics of thechiller. The information recorded on the log sheet can also be very helpful fordiagnosing potential problems in the system.4.0 Pressure ReadingsThe operating suction and discharge pressures in the system are directly related towater flow, condenser temperatures, chilled water set-points, and the cleanlinessof the system.For a R22 chiller at standard water-cooled conditions of 55º ECHW, 45º LCHW,85º ECW, 95º LCW the suction pressure should be approximately 64 psig and210 psig discharge pressure.All Multistack modules have a high pressure cut out safety device. The HP cutout for water-cooled MS modules is 300 psig for R-22, 320 psig for R-407C, and185 psig for R-134a.Each Multistack module also has a low pressure safety device. The LP cut out forMS modules with R-22, R-407C, or R-134a is 25 psig. .If circuits are faulting on HP the first action to be taken should be checking thecondenser water inlet filter cartridge for debris. See filter strainer cleaningprocedure in section 5.0.
A LP fault is an indication of low refrigerant charge in the system. If a circuit isgoing out on a LP fault check the static pressure of the system while the circuit isin the off mode. If pressures are low check the circuit for possible leaks. Thecircuit can be pressurized to 15 psig with refrigerant and topped to 160 psig withdry Nitrogen.5.0 Water TreatmentProper Water treatment is essential to ensure the peak efficiency and performanceof the chiller. The condenser and chilled water quality should be kept within thefollowing parameters to prevent any damage to the heat exchangers. The use ofhydrochloric, sulfuric, and muriatic acids as well as household bleach can causestress corrosion to the stainless steel in the heat exchangers. Use of these or anyother unapproved chemicals is not covered under the Multistack warranty.Multistack Water Guidelines● PH > 7 - < 9● TDS● Hardness● Alkalinity● Chlorides● Sulphates< 1000 ppm30 - 500 ppm30 - 500 ppm< 200 ppm< 200 ppm6.0 Strainer CleaningAll Multistack modules have a 30 mesh filter cartridge in the condenser andevaporator inlet header. The purpose for the filter cartridge is to keep debris fromentering the heat exchanger. An external “Y” or basket type system strainershould also be installed as a pre-filter to the Multistack strainers.There is no set time for cleaning the filter cartridges. The frequency of thisprocess is dependant on the water quality in the condenser and / or evaporatorloop.Normally, debris in a water loop is going to take the path of least resistance andbuild up on the last modules to receive water. Multistack modules come with anauto blow down (the DDRS-210A) installed on the condenser side of the lastmodule to receive water flow. The DDRS-210A is controlled by a timer in themaster control; it opens once a day to remove debris from the loop. The DDRS-
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Water Cooled Modules OPERATION & MAINTENANCE - Multistack

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