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

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

Carrier 19XRV Start-up, Operation And Maintenance Instructions Manual Manual pdf 39 page image

Ramp Loading -- Tile rmnp loading control slows downtile rate at which the compressor loads up. This control can pre-vent the compressor fiom loading up during the short period oftime when tile chiller is started and tile chilled water loop has tobe brought down to CONTROL POINT. This helps reduceelectlical demand charges by slowly bringing the chilled waterto CONTROL POINT. The total power draw during this periodremains ahnost unchanged.There are several methods of romp loading with the PIC III.Ramp loading can be based on LEAVING CHILLED WATER,ENTERING CHILLED WATER, PERCENT LINE CURENT orPERCENT MOTOR KILOWATFS. PULLDOWN RAMPTYPE is selected fiom tile RAMP DEM screen.1. Temperature ramp loading (TEMP PULLDOWN DE(;/MIN) limits the degrees per minute rote at which eitherLEA VING CHILLED WATER or ENTERING CHILLEDWATER temperature decreases. This rate is configured bythe operator on the TEMP_CTL screen.NOTE: If chiller control power has been off for 3 hours ormore, file next startup (only) will follow temperature ramploading using the minimum rate regardless of the rmnp loadingmethod and rate which m:e configured in the screens. This isused to maximize oil reclaim during stmtup.2. Motor load ramp loading (AMPS OR KW RAMP %/MINI limits the rate at which tile compressor motor cur-rent or complessor motor load increases. The AMPS ORKW RAMP %/MIN rate is configured by the operatoron the RAMP_DEM screen in line current or motorkilowatts.If kilowatts is selected for the DEMAND LIMIT SOURCE,the MOTOR RATED LOAD KILOWATTS must be entered inthe VFD_CONF screen.The TEMP PULLDOWN DEG/MIN may be viewed ormodified on the TEMP_CTL screen which is accessed fromthe EQUIPMENT SERVICE screen. PULLDOWN RAMPTYPE, DEMAND LIMIT SO URCE, and AMPS OR KW RAMP_/MIN may be viewed or modified on the RAMP_DEMscreen.Capacity Override (Table 7) -- Capacity overrides canprevent some safety shutdowns caused by exceeding the motoramperage limit, low evaporator temperature safety limit, highmotor temperature safety limit, and high condenser pressurelimit. In all cases there are two stages of compressor capacitycontrol applied by guide vane operation.1. When the value of interest crosses the First Stage Setpoint into the Override Region, the guide vanes areprevented from opening furthel: and the status line on theICVC indicates the reason for the override. Normalcapacity control operation is restoled when the valuecrosses back over the First Stage Set point, leaving theOverride Region. (Refer to Table 7.)2. When the value of interest is in the Override Region andfurther crosses the Second Stage Set point, the guidevanes me closed until the value meets the OvenideTermination Condition. The PIC III controls resumenorm_d capacity control operation after the overridetermination condition has been satisfied. (In the case ofhigh dischmge supeflleat, there is an intermediate stage).Whenever the motor current demand limit set point(ACTIVE DEMAND LIMIT) is reached, it activates a capacityovenide, again, with a 2-step process. Exceeding 110% of therated load amps for more than 30 seconds will initiate a safetyshutdown.The high compressor lift (surge prevention) set point willcause a capacity ovenide as well. When the surge preventionset point is reached, the controller normally will only preventthe guide vanes from opening. If so equipped, the hot gasbypass valve will open instead of holding the vanes. The hotgas bypass will only open if the compressor is at 100% speed.See the Surge Prevention Algorithm section, page 42.High Discharge Temperature Control -- If theCOMP DISCltARGE TEMP increases above 160 F (71.1 C),the guide vanes _ue proportionally opened to increase gas flowthrough the compressol: If the LEAVING CHILLED WATERtemperature decreases 5 ° F (2.8 ° C) below the control set pointtemperature, as a result of opening the guide vanes, the PIC IIIwill bring the chiller into the recycle mode.Oil Sump Temperature and Pump Con-trol -- The oil sump telnperature is regulated by the PIC III,with the oil heater relay when the chiller is shut down.As part of the pre-start checks executed by the controls, theoil sump temperature (OIL SUMP TEMP) is compared tothe cooler refrigerant temperature (EVAPORATOR REFRIGTEMP) if the OIL SUMP TEMP is less than 150 F (65.6). Ifthe diffelence between these 2 temperatures is 50 F (27.8 C) orless, the start-up will be delayed until either of these conditionsis no longer true. Once this temperature criteria is satisfied, thestart-up continues.The oil heater relay is energized whenever the chiller com-pressor is off and the oil sump temperature is less than 140 F(60.0 C) or the OIL SUMP TEMP is less than the EVAPREFRIG TEMP plus 53 ° F (29.4 ° C). The oil heater is turnedoff when the OIL SUMP TEMP is either:• morethan 152 F (66.7 C), or• more than 142 F (61.1 C) and more than the EVAPREFRIG TEMP plus 55 ° F (30.6 ° C).The oil heater is always off during start-up or when thecompressor is running.The oil pump is also energized dnring the time the oil is be-ing heated (for 30 seconds at the end of every 30 minutes).The oil pump will not operate if the EVAPORATOR PRES-SURE is less than -5 psig (-34.5 kPa).Oil Cooler -- The oil must be cooled when the compres-sor is running. This is accomplished through a small, plate-typeheat exchanger (also called the oil cooler) located behind theoil pump. The heat exchanger uses liquid condenser refrigerantas the cooling liquid. Refrigerant thermostatic expansionvalves (TXVs) regulate refrigerant flow to control the oil tem-perature entering the bearings. The bulbs for the expansionvalves are strapped to the oil supply line leaving the heatexchangel: and the valves are set to maintain 110 F (43 C).NOTE: The TXVs me not adjustable. The oil sump tempemtmemay be at a lower temperature during compressor operation.39