Carrier AQUASNAP 30RAP010-150 Controls, Start-up, Operation, Service, And Troubleshooting

Also see for AQUASNAP 30RAP010-150: Start up & operation manual Installation instructions Installation instructions Controls, start-up, operation, service, and troubleshooting

Carrier AQUASNAP 30RAP010-150 Controls, Start-up, Operation, Service, And Troubleshooting Manual pdf 30 page image

30First Stage Override — If the current capacity stage is zero,the control will modify the routine with a 1.2 factor on addingthe first stage to reduce cycling. This factor is also appliedwhen the control is attempting to remove the last stage ofcapacity.Slow Change Override — The control prevents the capacitystages from being changed when the leaving fluid temperatureis close to the set point (within an adjustable deadband) andmoving towards the set point.Ramp Loading — Ramp loading (Configura-tionSLCTCRMP) limits the rate of change of leavingfluid temperature. If the unit is in a Cooling mode and config-ured for Ramp Loading, the control makes 2 comparisons be-fore deciding to change stages of capacity. The control calcu-lates a temperature difference between the control point andleaving fluid temperature. If the difference is greater than 4° F(2.2° C) and the rate of change (°F or °C per minute) is morethan the configured Cooling Ramp Loading value (CRMP),the control does not allow any changes to the current stage ofcapacity.Low Entering Fluid Temperature Unloading — When theentering fluid temperature is below the control point, thecontrol will attempt to remove 25% of the current stages beingused. If exactly 25% cannot be removed, the control removesan amount greater than 25% but no more than necessary. Thelowest stage will not be removed.Minimum Load Control — If equipped, the minimum loadcontrol valve is energized only when one compressor is run-ning on Circuit A and capacity is decreasing, provided that theminimum run time for Circuit B compressors has been satis-fied. If the close control feature is enabled, the minimum loadcontrol valve may be used as needed to obtain leaving fluidtemperature close to set point.Cooler Freeze Protection — The control will try to preventshutting the chiller down on a Cooler Freeze Protection alarmby removing stages of capacity. If the cooler fluid selectedis Water, the freeze point is 34 F (1.1 C). If the cooler fluidselected is Brine, the freeze point is the Brine Freeze Point (SetPointsFRZBR.FZ). This alarm condition (A207) onlyreferences leaving fluid temperature and NOT Brine Freezepoint. If the cooler leaving fluid temperature is less than thefreeze point plus 2.0° F (1.1° C), the control will immediatelyremove one stage of capacity. This can be repeated once every30 seconds.Low Saturated Suction Protection — The control will try toprevent shutting a circuit down due to low saturated suctionconditions by removing stages of capacity. These circuit alertconditions (T116, T117) compare saturated suction tempera-ture to the configured Brine Freeze Point (SetPointsFRZBR.FZ). The Brine Freeze point is a user-configurable value that must be left at 34 F (1.1 C) for 100%water systems. A lower value may be entered for systems withbrine solutions, but this value should be set according to thefreeze protection level of the brine mixture. Failure to properlyset this brine freeze point value may permanently damage thebrazed plate heat exchanger. The control will initiate Mode 7(Circuit A) or Mode 8 (Circuit B) to indicate a circuit’s capaci-ty is limited and that eventually the circuit may shut down.Head Pressure Control — The main base board(MBB) controls the condenser fans to maintain the lowestcondensing temperature possible, and thus the highest unitefficiency. The MBB uses the saturated condensing tempera-ture input from the discharge pressure transducer and outsideair temperature sensor to control the fans. Head pressure con-trol is maintained through a calculated set point which is auto-matically adjusted based on actual saturated condensing andsaturated suction temperatures so that the compressor(s) arealways operating within the manufacturer’s specified enve-lope (Fig. 20A and 20B). If OAT is greater than 70 F before acircuit is starting, then all condenser fan stages will be ener-gized. A fan stage is increased based on SCT (saturated con-densing temperature). When the highest SCT is greater thanthe Fan On Set Point (Set PointsHEADF.ON), then anadditional stage of fan will be added to the current fan stage.Fan On Set Point (F.ON) equals Head Set Point (SetPointsHEADH.DP) except after a fan stage increasewhen the Head Set Point is increased by Fan Stage Delta (SetPointsHEADF.DLT). A fan stage is decreased when theSCTs of both circuits are less than the Fan Off Set Point (SetPointsHEADF.OFF) for two minutes. Table 10 showsthe number of fan stages, contactors energized and the fans thatare on during the fan stage. Unit sizes 035 to 060 have com-mon fan control. Figure 21 shows the location of each fan andcontrol box within the unit.474645444342410 200 400 600 800 1000TIME (SECONDS)2 STARTS3 STARTSDEADBAND EXAMPLELWT (F)MODIFIEDDEADBANDSTANDARDDEADBAND8765LWT (C)Fig. 19 — Deadband MultiplierLEGENDLWT — Leaving Water Temperature