Carrier GEMINI 38APD025-100 Operating And Service Manual

Also see for GEMINI SELECT 38APD025: Installation instructions Manual Installation instructions

Carrier GEMINI 38APD025-100 Operating And Service Manual Manual pdf 26 page image

26MINUTES LEFT FOR START — This value is displayedonly in the network display tables (using Service Tool,ComfortVIEW™ or ComfortWORKS® software) andrepresents the amount of time to elapse before the unit will startits initialization routine. This value can be zero without themachine running in many situations. This can include beingunoccupied, ENABLE/OFF/REMOTE CONTACT switch inthe OFF position, CCN not allowing unit to start, DemandLimit in effect, no call for cooling due to no load, and alarm oralert conditions present. If the machine should be running andnone of the above are true, a minimum off time (DELY, seebelow) may be in effect. The machine should start normallyonce the time limit has expired.MINUTES OFF TIME (Configuration OPT2DELY) — This user-configurable time period is used bythe control to determine how long unit operation is delayedafter power is applied/restored to the unit. Typically, this timeperiod is configured when multiple machines are located on asingle site. For example, this gives the user the ability to pre-vent all the units from restarting at once after a power failure.A value of zero for this variable does not mean that the unitshould be running.NOTE: If the unit has digital scroll or hot gas bypass, circuit Ais always lead.LEAD/LAG DETERMINATION — This is a configurablechoice and is factory set to be automatic for all units. The valuecan be changed to Circuit A or Circuit B leading as desired. Setat automatic, the control will sum the current number of loggedcircuit starts and one-quarter of the current operating hours foreach circuit. The circuit with the lowest sum is started first.Changes to which circuit is the lead circuit and which is the lagare also made when total machine capacity is at 100% or whenthere is a change in the direction of capacity (increase ordecrease) and each circuit’s capacity is equal.CAPACITY CONTROL OVERRIDES — The following over-rides will modify the normal operation of the routine.Deadband Multiplier — The user configurable deadband mul-tiplier (Configuration SLCT Z.GN) has a default value of1.0. The range is from 1.0 to 4.0. When set to other than 1.0,this factor is applied to the capacity Load/Unload Factor. Thelarger this value is set, the longer the control will delay betweenadding or removing stages of capacity.First 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 — This control prevents the capacitystages from being changed when the supply temperature isclose to the set point (within an adjustable deadband) and mov-ing toward the set point.Ramp Loading — The ramp loading control (ConfigurationSLCT CRMP) limits the rate of change of supply temper-ature. If the unit is in a Cooling mode and configured for RampLoading, the control makes 2 comparisons before deciding tochange stages of capacity. The control calculates a temperaturedifference between the control point and supply temperature. Ifthe difference is greater than 4° F (2.2° C) and the rate ofchange (°F or °C per minute) is more than the configured Cool-ing Ramp Loading value (CRMP), the control does not allowany changes to the current stage of capacity.Minimum Load Control — If equipped, the minimum loadcontrol valve is energized only when one compressor on thecircuit is running and the unit is unloading.Low Saturated Suction Protection — The control will try toprevent shutting a circuit down due to low saturated suctionconditions by removing stages of capacity. See Alerts section.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. If OAT is greaterthan 70 F before a circuit is starting, then all condenser fanstages will be energized. A fan stage is increased based onSCT. When the highest SCT of both circuits is greater than fanon set point, then an additional stage of fan will be added to thecurrent fan stage. Fan On Set Point (F.ON) equals Head SetPoint ON (115 F) except after a fan stage increase when HeadSet Point is increased by Fan Stage Delta (10 F). A fan stage isdecreased when the SCTs of both circuits are less than fan offset point for two minutes. Fan Off Set Point (F.OFF) equalsHead Set Point OFF (–72 F). Table 9 shows the number of fanstages, contactors energized and the fans that are on during thefan stage. Unit sizes 025 to 060 have common fan control. Unitsizes 070 to 100 have some fans that are common and somethat are controlled individually. Figure 30 shows the locationof each fan and compressor within the unit.MOTORMASTER ® V OPTION — For low-ambient opera-tion, the first stage of fans is equipped with the Motormaster Vhead pressure controller option or accessory. For units withcommon fans, the control will control the Head Pressure Set-point (–10 F) and the highest SCT to try to maintain it at 100 F.Unit sizes 070 to 100 have one Motormaster V for each circuitand the control tries to maintain SCT at 100 F for the circuit.The controller is given an ON command with the first stage offan and adjusts fan speed.Table 9 — Fan Stages* Fan Stage 1 on unit size 070 is used only when ambient temperature is less than 32 F.  38AP UNIT SIZE CIRCUIT A STAGES/COMMON FAN STAGES CIRCUIT B FAN STAGESFan Stage Contactor Energized Fans Operating Fan Stage Contactor Energized Fans Operating025-030 Stage 1Stage 2FC1FC1,2OFM1OFM1,2 — — —040,050Stage 1Stage 2Stage 3FC1FC2FC1,2OFM3OFM1,2OFM1,2,3— — —060Stage 1Stage 2Stage 3Stage 4FC1FC2FC1,2FC1,2,3OFM3OFM1,2OFM1,2,3OFM1,2,3,4— — —070 Stage 1*Stage 2Stage 3FC2,4FC1FC1,3OFM1,2OFM3OFM3,4Stage 1*Stage 2Stage 3FC1,3FC2FC2,4OFM3,4OFM1OFM1,2080Stage 1Stage 2FC1FC1,3OFM5OFM5,6,(2)Stage 1Stage 2Stage 3FC4FC3,4FC2,3,4OFM3OFM3,2,(6)OFM3,1,2,(6)090,100Stage 1Stage 2Stage 3Stage 4Stage 5Stage 6FC4FC1FC4,1FC4,3FC1,3FC4,1,3OFM3OFM5OFM3,5OFM3,(2),4,6OFM5,(2),4,6OFM3,5,(2),4,6Stage 1Stage 2Stage 3Stage 4Stage 5Stage 6FC4FC2FC4,2FC4,3FC2,3FC4,2,3OFM3OFM1OFM3,1OFM3,2,4,(6)OFM1,2,4,(6)OFM3,1,2,4,(6)