Carrier 19XR Start-up, Operation And Maintenance Instructions Manual

Also see for HERMETIC CENTRIFUGAL LIQUID CHILLERS 19XR: User manual Start-up and service instructions Installation instructions Product data Installation instructions

Contents

Carrier 19XR Start-up, Operation And Maintenance Instructions Manual Manual pdf 38 page image

(REMOTE TEMP [FULL RESET]). Then, enter the maxi-mum amount of reset required to operate the chiller(DEGREES RESET). Reset Type 2 can now be activated.RESET TYPE 3 — Reset Type 3 is an automatic chilled wa-ter temperature reset based on cooler temperature differ-ence. Reset Type 3 adds ± 30° F (± 16° C) based on thetemperature difference between the entering and leaving chilledwater temperature.To configure Reset Type 3, enter the chilled water tem-perature difference (the difference between entering andleaving chilled water) at which no temperature reset occurs(CHW DELTA T [NO RESET]). This chilled water temper-ature difference is usually the full design load temper-ature difference. Next, enter the difference in chilled watertemperature at which the full amount of reset occurs (CHWDELTA T [FULL RESET]). Finally, enter the amount of re-set (DEGREES RESET). Reset Type 3 can now be activated.Demand Limit Control Option — The demand limitcontrol option (20 mA DEMAND LIMIT OPT) is externallycontrolled by a 4 to 20 mA or 0 to 5 vdc signal from anenergy management system (EMS). The option is set up onthe RAMP_DEM screen. When enabled, 4 mA is the 100%demand set point with an operator-configured minimum de-mand at a 20 mA set point (DEMAND LIMIT AT 20 mA).The auto. demand limit is hardwired to terminals J5-5 (−)and J5-6 (+) on the CCM. Switch setting number 1 on SW2will determine the type of input signal. With the switch setat the ON position the input is configured for an externallypowered 4 to 20 mA signal. With the switch in the OFFposition the input is configured for an external 0 to 5 vdcsignal.Surge Prevention Algorithm — This is an operator-configurable feature that can determine if lift conditions aretoo high for the compressor and then take corrective action.Lift is defined as the difference between the pressure at theimpeller eye and at the impeller discharge. The maximumlift a particular impeller wheel can perform varies with thegas flow across the impeller and the size of the wheel.A surge condition occurs when the lift becomes sohigh the gas flow across the impeller reverses. This condi-tion can eventually cause chiller damage. The surge preven-tion algorithm notifies the operator that chiller operatingconditions are marginal and to take action to help preventchiller damage such as lowering entering condenser watertemperature.The surge prevention algorithm first determines if cor-rective action is necessary. The algorithm checks 2 sets ofoperator-configured data points, the minimum load points (MIN.LOAD POINT [T1/P1]) and the full load points (FULLLOAD POINT [T2/P2]). These points have default settingsas defined on the OPTIONS screen or on Table 4.The surge prevention algorithm function and settings aregraphically displayed in Fig. 19 and 20. The two sets of loadpoints on the graph (default settings are shown) describe aline the algorithm uses to determine the maximum lift of thecompressor. When the actual differential pressure betweenthe cooler and condenser and the temperature difference be-tween the entering and leaving chilled water are above theline on the graph (as defined by the minimum and full loadpoints), the algorithm goes into a corrective action mode. Ifthe actual values are below the line and outside of the dead-band region, the algorithm takes no action. When the pointdefined by the ACTIVE DELTA P and ACTIVE DELTA T,moves from the region where the HOT GAS BYPASS/SURGE PREVENTION is off, the point must pass throughthe deadband region to the line determined by the config-ured valves before the HOT GAS BYPASS/SURGEPREVENTION will be turned on. As the point moves fromthe region where the HOT GAS BYPASS/SURGEPREVENTION is on, the point must pass through the dead-band region before the HOT GAS BYPASS/SURGE PRE-VENTION is turned off. Information on modifying the de-fault set points of the minimum and full load points may befound in the Input Service Configurations section, page 53.Corrective action can be taken by making one of 2 choices.If a hot gas bypass line is present and the hot gas optionis selected on the OPTIONS table (SURGE LIMIT/HGBPOPTION is set to 1), the hot gas bypass valve can be ener-gized. If the hot gas bypass option is not selected (SURGELIMIT/HGBP OPTION is set to 0), hold the guide vanes.See Table 4, Capacity Overrides. Both of these correctiveactions try to reduce the lift experienced by the compressorand help prevent a surge condition.LEGENDECW — Entering Chilled WaterHGBP — Hot Gas BypassLCW — Leaving Chilled WaterDP = (Condenser Psi) − (Cooler Psi)DT = (ECW) − (LCW)Fig. 19 — 19XR Hot Gas Bypass/SurgePrevention with Default English SettingsLEGENDECW — Entering Chilled WaterHGBP — Hot Gas BypassLCW — Leaving Chilled WaterDP = (Condenser kPa) − (Cooler kPa)DT = (ECW) − (LCW)Fig. 20 — 19XR Hot Gas Bypass/SurgePrevention with Default Metric Settings38