YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls

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SECTION 4 - INSTALLATION WATER TREATMENT The unit performance provided in the Design Guide is based on a fouling factor of 0.018m2/hr °C/kW (0.0001 ft2hr°F/Btu). Dirt, scale, grease and certain types of water treatment will adversely affect the heat exchanger surfaces and therefore the unit performance. Foreign matter in the water system(s) can increase the heat exchanger pressure drop, reducing the flow rate and causing potential damage to the heat exchanger tubes. Aerated, brackish or salt water is not recommended for use in the water system(s). Johnson Controls recommends that a water treatment specialist should be consulted to determine whether the proposed water composition will adversely affect the evaporator materials of carbon steel and copper. The pH value of the water flowing through the evaporator must be kept in a range between 7 and 8.5. PIPEWORK ARRANGEMENT The following is a suggested piping arrangement for single unit installations. FIGURE 6 - PIPEWORK ARRANGEMENT 26 -Isolating Valve - Normally Open -Isolating Valve - Normally Closed -Flow Regulating Valve -Flow Measurement Device -Strainer -Pressure Tapping -Flow Switch -Flanged Connection -Pipework MINIMUM WATER VOLUME LD15151 It is good practice to include as much water volume as possible in a chilled water loop. This increases the thermal mass and “Flywheel” effect within the system (i.e. the more; the better) which in turn promotes stable water temperature control and increases reliability by reducing compressor cycling. FORM 201.28-NM1.1 ISSUE DATE: 8/29/2012 For air conditioning applications, a minimum of 3 gallons/ton is required. It is preferred that the gallon/ton ratio be within the 5 to 8 range. For process applications, a minimum of 6 gallons/ton ratio is required with preference towards a range of 7 to 11. Install a tank or increase pipe sizes to provide sufficient water volume. LEAVING WATER TEMPERATURE OUT OF RANGE The YVAA chiller line has a maximum leaving water temperature of 15.6°C (60°F). Where process applications require a chilled water temperature higher than what the chiller provides, a simple piping change can remove the problem. By using a mixture of chillercooled water and returning process water, the chilled water entering the process can be held at the desired temperature. A tank can also be used to meet high leaving water temperature requirements. SUPPLY TO LOAD RECIRCULATION LOAD FIGURE 7 - LEAVING WATER TEMPERATURE OUT OF RANGE SUGGESTED LAYOUT FLOW RATE OUT OF RANGE RETURN FROM LOAD LD15049 Each YVAA evaporator has a minimum and maximum flow rate. Some process applications require a flow rate that is out of range for the evaporator. In those applications, a piping change can remove the problem. In applications where the required flow rate is less than the evaporator’s minimum allowable, the chilled water can be recirculated to the chiller. JOHNSON CONTROLS
FORM 201.28-NM1.1 ISSUE DATE: 8/29/2012 SUPPLY TO LOAD LOAD BYPASS RETURN FROM LOAD LD15049 FIGURE 8 - SUGGESTED LAYOUT FOR APPLICA- TIONS WITH A FLOW RATE LESS THAN THE EVAPORATOR MINIMUM ALLOW- ABLE FLOW RATE In applications where the required flow rate is greater than the evaporator’s maximum allowable, the chilled water can be recirculated to the load. SUPPLY TO LOAD FIGURE 9 - SUGGESTED LAYOUT FOR APPLICA- TIONS WITH A FLOW RATE LESS THAN THE EVAPORATOR MINIMUM ALLOW- ABLE FLOW RATE THERMAL STORAGE LOAD BYPASS RETURN FROM LOAD LD15049 Thermal storage is the practice of storing cooling energy during a period of little or no load and/or low energy costs for use during periods of high load and/or energy costs. Conventional cooling systems produce cooling SECTION 4 - INSTALLATION when it is needed which is commonly during times of peak demand. Thermal storage allows generation of cooling capacity to occur during off-peak periods and store that capacity to meet future cooling requirements. Using thermal storage can result in smaller equipment sizes, thereby reducing capital cost, and also can result in significant energy cost savings The YVAA has special control logic to be able to produce chilled leaving brine temperatures below 4.4°C (40°F) so as to supply a storage tank with chilled liquid during times of low demand. YVAA chillers selected for thermal storage operation can also be selected to efficiently provide chilled fluid at nominal cooling loads. VARIABLE PRIMARY FLOW Johnson Controls recommends a maximum 10% per minute flow rate of change, based on design flow, for variable primary flow applications. Provide 8 to 10 gallons per chiller ton (8.6 to 10.8 liter per cooling KW) system water volume. Insufficient system volume and rapid flow changes can cause control problems or can even cause chiller shutdowns. There are many other design issues to evaluate with variable primary flow systems. Consult your Johnson Controls Sales Office for more information about successfully applying YVAA chillers. CONNECTION TYPES AND SIZES For connection sizes relevant to individual models refer to SECTION 5 - TECHNICAL DATA. EVAPORATOR CONNECTIONS Standard chilled liquid connections on evaporators are of the Victaulic Groove type for ASME and PED marked units and Flange type for GB marked units (see Figure 11 on page 28 for flange dimensions on GB marked vessels). FIGURE 10 - VICTAULIC GROOVE LD10494 JOHNSON CONTROLS 27 4
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YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls

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