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

Also see for AquaEdge 19XRV series: Start-up, operation and maintenance instructions Start-up and service instructions Installation instructions Start-up, operation and maintenance instructions Start-up and service instructions

Contents

355.1.6 - Demand limitingThe PIC III controls provide a feature for limiting AVE-RAGE LINE CURRENT or LINE KILOWATTS (demand)by limiting capacity via guide vane control. The limit appliedis called ACTIVE DEMAND LIMIT, which is equal to aBASE DEMAND LIMIT value (set in the SETPOINTSScreen, page 0, default value 100%), or that determinedby AUTO DEMAND LIMIT INPUT (an optional 4 to 0mA input, described below). ACTIVE DEMAND LIMITmay also be forced to be different from BASE DEMANDLIMIT by manually overriding the value (forcing) from theMAINSTAT screen or writing a value via a CCN networkdevice, or controlled by another chiller in Lead Lagoperation (see page 44).The demand limit may be based on either line current or kW,as indicated by DEMAND LIMIT SOURCE in theEQUIPMENT SERVICE/RAMP_DEM table. The defaultis 0, for demand limiting based on AVERAGE LINECURRENT (percent of RATED LINE AMPS, as displayedon the default screen). Setting DEMAND LIMIT SOURCEto 1 makes demand limiting based on PERCENT LINEKILOWATTS (displayed in the MAINSTAT screen).LINE KILOWATTS is measured by the VFD, and theMOTOR RATED LOAD kW value (100% rated kW) isset in the VFD_CONF table.If the DEMAND LIMIT SOURCE (percent line current)exceeds the ACTIVE DEMAND LIMIT by 5% or less,increases in guide vane opening will be prevented. If theDEMAND LIMIT SOURCE (percent line current) exceedsthe ACTIVE DEMAND LIMIT by more than 5%, theguide vanes will be forced to close. Also, as the DEMANDLIMIT SOURCE approaches the ACTIVE DEMANDLIMIT from a lower value, allowable capacity increasesbecome increasingly more limited, beginning when theDEMAND LIMIT SOURCE is within the DEMANDLIMIT PROP BAND (configurable in the RAMP_DEMtable).5.1.7 - Demand limit control optionThe demand limit control option (0 mA DEMAND LIMITOPT) is externally controlled by a 4 to 0 mA signal froman energy management system (EMS). The option is set upon the RAMP_DEM screen. When enabled, 4 mA will setACTIVE DEMAND LIMIT to 100% of the DEMANDLIMIT SOURCE (regardless of the value of BASEDEMAND LIMIT), and 0 mA will set ACTIVEDEMAND LIMIT to the value configured as “0MADEMAND LIMIT OPT” in the RAMP_DEM table.Wire the auto demand limit input to terminals J5-1 (–) andJ5- (+) on the CCM. In order to use a 1 to 5 V d.c. inputinstead of 4 to 0 mA, install a 5-ohm resistor in serieswith the + lead at terminal J5-.A DEMAND KILOWATTS monitoring feature is alsoavailable. This feature provides a display of average demand(power) in kilowatts (in the POWER screen). This value iscontinuously updated and averaged over the precedingtime interval specified as DEMAND WATTS INTERVALin the SERVICE / EQUIPMENT SERVICE/RAMP_DEMscreen.5.2 - Chiller timers and starts counterThe PIC III maintains two run time clocks:COMPRESSOR ONTIME and SERVICE ONTIME.COMPRESSOR ONTIME indicates the total lifetimecompressor run hours. SERVICE ONTIME is a resettabletimer that can be used to indicate the hours since the lastservice visit or any other event. A separate counter talliescompressor starts as TOTAL COMPRESSOR STARTS.All of these can be viewed on the MAINSTAT screen onthe ICVC. Both ontime counters roll over to 0 at 500,000hours. Manual changes to SERVICE ONTIME from theICVC are permitted at any time. If the controller is replaced,one opportunity, before the first startup with the newcontroller, is provided to set COMPRESSOR ONTIMEand TOTAL COMPRESSOR STARTS to the last readingsretained with the prior controller. The SERVICE ONTIMEtimer can register up to 3,767 hours before it rolls over tozero.The chiller also maintains a start-to-start timer and a stop-to-start timer. These timers limit how soon the chiller canbe started. START INHIBIT TIMER is displayed on theMAINSTAT screen. See the Start-Up/Shutdown/RecycleSequence section, page 51, for more information on thistopic.5.3 - Occupancy scheduleThe chiller schedule, described in the Time ScheduleOperation section (page 19), determines when the chillercan run. Each schedule consists of from 1 to 8 occupied orunoccupied time periods, set by the operator. The chillercan be started and run during an occupied time period(when OCCUPIED? is set to YES on the MAINSTATdisplay screen). It cannot be started or run during anunoccupied time period (when OCCUPIED? is set to NOon the MAINSTAT display screen). These time periodscan be set for each day of the week and for holidays. Theday begins with 00.00 hours and ends with 4.00 hours. Thedefault setting for OCCUPIED? is YES, unless an unoccu-pied time period is in effect.These schedules can be set up to follow a building’s occu-pancy schedule, or the chiller can be set so to run 100% ofthe time, if the operator wishes. The schedules also can bebypassed by forcing the CHILLER START/STOP parameteron the MAINSTAT screen to START. For more informationon forced starts, see Local start-up, page 51.The schedules also can be overridden to keep the chiller inan occupied state for up to 4 hours, on a one time basis.See the Time Schedule Operation section, page 19.Fig. 8 shows a schedule for a typical office building with a3-hour, off-peak, cool-down period from midnight to 3 a.m.,following a weekend shutdown. Holiday periods are in anunoccupied state 4 hours per day. The building operatesMonday through Friday, 7:00 a.m. to 6:00 p.m., and Satur-days from 6:00 a.m. to 1:00 p.m. This schedule also includesthe Monday midnight to 3:00 a.m. weekend cool-downschedule.