Carrier 48MPD Installation, Start-up And Service Instructions Manual

Contents

Control Loop CheckoutThe checkout and adjustment of control loops shouldonly be done by certified Carrier Comfort Network(CCN) technicians. The following checkout procedureis offered as a guide and presumes the user has obtainedbasic knowledge of controls through CCN training.TO CHECK OPERATION OF ANALOG OUTPUTS — Thecontrol algorithms of the unit controls utilize the master/submaster loop concept. The master loop monitors themaster sensor (the sensor which tries to maintain the desiredset point), and calculates the submaster reference required todo so. The submaster loop monitors the submaster sensorand controls the actual output to the controlled device.These algorithms require the adjustment of a number ofgain values to function properly. The 48/50MP units comewith preset default values. However, it may be necessary toadjust several of these values to achieve stable control. Thesevalues are submaster loop gain (SMG), submaster loop cen-ter value (SCV), and master loop gain (MLG). In addition,proportional, integral, and derivative multiplier values canbe accessed through the Building Supervisor, Service Tool,or ComfortWorks™ software.To verify or adjust submaster default values, perform thefollowing for each controlled device (control loop):1. Verify that the system is in the Occupied mode and thesupply-air fan is running.2. Verify that the supply-air fan status indicates ON. If thefan status is OFF, the unit control algorithms will dis-able all routines.3. Verify that all forced values have been removed.4. Table 27 indicates recommended starting values for MLGand SMG for 48/50MP units. Verify that these valueshave been entered by checking the service function.5. Verify/adjust the SMG. If the SMG is too large, the loopwill tend to oscillate (hunt). If it is too small, the loopwill react too slowly.Verify or adjust the SMG as follows:Using the HSIO keypad, force the submaster referenceof the control loop to a value above or below the actualsensor reading. Verify that the actuator responds cor-rectly. If the actuator drives in the wrong direction, goto the submaster gain (SMG) for the control loop andreverse the sign of the gain.For example: If the submaster loop gain is 5.0, changeit to -5.0.6. Observe the operation of the controlled device for a fewminutes. If the device oscillates every few seconds aroundthe forced value, then lower the SMG by small amountsuntil the output steadies. If the output to the device re-sponds to a change in the temperature in small incre-ments, then increase the SMG in small amounts untilthe output steadies.NOTE: Do not be alarmed if the submaster sensor sta-bilizes at a value greater or less than the forced value.This is called the submaster droop offset and is normal.7. It is not necessary to adjust the submaster loop centervalue, as the master loop will adjust the submaster ref-erence as required to satisfy its set point. However, itmay be desirable to keep the submaster droop to a mini-mum. This is most often required for economizer loops.If the submaster droop is too large, adjust the SCV asfollows:If the submaster droop is positive (actual value greaterthan reference value), the SCV should be decreased forHCV (heating coil) and IGV (supply fan VFD) loopsand increased for CC (cooling control) and ECON (econo-mizer) loops.If the submaster droop is negative (actual value less thanreference value), the SCV should be increased for HCVand IGV loops and decreased for CC and ECON loops.Table 27 — 48/50MP Units SMG, SCV and MLG Recommended Starting ValuesFUNCTION/GAIN OR SCV SERVICESUBFUNCTION(HSIO)GAIN VALUECV Application VAV ApplicationCooling ControlMLG 8 1.0 1.0EconomizerMLG 10 1.0 1.0SMG 10 −7.5 −7.5SCV 10 50 50Duct Pressure (VFD)MLG 9 N/A 1.0SMG 9 N/A 2.0*SCV 9 N/A 35*Building PressureMLG 18 1.0 1.0SMG 18 −5.0 −5.0SCV 18 50 50Staged HeatMLG † 11 1.0 1.0SMG † 11 5.0 5.0Heating CoilMLG 7 1.0 1.0SMG 7 7.5 7.5SCV 7 50 50HumidifierMLG 17 1.0 1.0SMG 17 7.5 7.5SCV 17 50 50*Factory setting; differs from new control setting.†48MP only.LEGENDCV — Constant VolumeMLG — Master Loop GainSCV — Submaster Center ValueSMG — Submaster Loop GainVAV — Variable Air Volume41