Carrier 30GTN Service And Troubleshooting Manual

Also see for 30GTN: Product data Installation instructions Installation instructions

Carrier 30GTN Service And Troubleshooting Manual Manual pdf 43 page image

Table 23 — Alarms Mode and Sub-Mode DirectorySUB-MODE KEYPAD ENTRY ITEM ITEM EXPANSION COMMENTCRNT ENTER AXXX or TXXX CURRENTLY ACTIVE ALARMS Alarms are shown as AXXX.Alerts are shown as TXXX.RCRN ENTER YES/NO RESET ALL CURRENT ALARMSHIST ENTER AXXX or TXXX ALARM HISTORY Alarms are shown as AXXX.Alerts are shown as TXXX.RHIS ENTER YES/NO RESET ALARM HISTORYTable 24 — Example of Reading and Clearing AlarmsSUB-MODE KEYPAD ENTRY ITEM ITEM EXPANSION COMMENTCRNT ENTER AXXX or TXXX CURRENTLY ACTIVE ALARMS ACTIVE ALARMS (AXXX) ORALERTS (TXXX) DISPLAYED.CRNT ESCAPERCRNNO Use to clear active alarms/alertsENTER NO NO FlashesYES Select YESENTER NO Alarms/alerts clear, YES changes to NOTemperature Reset — The control system is capableof handling leaving-fluid temperature reset based on returncooler fluid temperature. Because the change in temperaturethrough the cooler is a measure of the building load, the re-turn temperature reset is in effect an average building loadreset method. The control system is also capable of tempera-ture reset based on outdoor-air temperature (OAT), space tem-perature (SPT), or from an externally powered 4 to 20 mAsignal. Accessory sensors must be used for OAT and SPTreset (HH79NZ014 for OAT and HH51BX006 for SPT). TheEnergy Management Module (EMM) must be used for tem-perature reset using a 4 to 20 mA signal.To use the return reset, four variables must be configured.In the Configuration mode under the sub-mode RSET, itemsCRST, CRT1, CRT2, and DGRC must be set properly. SeeTable 25 on page 42 for correct configuration. See Fig. 2-4for wiring details.Under normal operation, the chiller will maintain a con-stant leaving fluid temperature approximately equal to thechilled fluid set point. As the cooler load varies, the enteringcooler fluid will change in proportion to the load as shownin Fig. 20. Usually the chiller size and leaving-fluid tem-perature set point are selected based on a full-load condi-tion. At part load, the fluid temperature set point may be colderthan required. If the leaving fluid temperature was allowedto increase at part load, the efficiency of the machine wouldincrease.Return temperature reset allows for the leaving tempera-ture set point to be reset upward as a function of the returnfluid temperature or, in effect, the building load.LEGENDEWT — Entering Water (Fluid) TemperatureLWT — Leaving Water (Fluid) TemperatureFig. 20 — Standard Chilled Fluid TemperatureControl — No Reset43