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

Also see for 48AJ: Installation instructions Operation and service guide Started guide Operating and service guide

Contents

88Table 41 — Smoke Control ModesLEGENDHEAD PRESSURE CONTROL — Each unit has a fan cy-cling, outdoor thermostat to shut off the outdoor-fan motor(s) at55 F (one outdoor-fan motor on 48AJ,AK,AW,AY020-030 and48EJ,EK,EW,EY024-034 units, 2 outdoor-fan motors on48AJ,AK,AW,AY035-050 and 48EJ,EK,EW,EY038-048 unitsand 3 outdoor-fan motors on 48AJ,AK,AW,AY060 and48EJ,EK,EW,EY054-068 units). The head pressure controlpermits unit to operate with correct condensing temperaturesdown to 35 F outdoor-air temperature.MOTORMASTER® III CONTROL — The Motormaster IIISolid-State Head Pressure Control is a field-installed accessoryfan speed control device actuated by a temperature sensor. Itis specifically designed for use on Carrier equipment and con-trols the condenser-fan motor speed in response to the saturatedcondensing temperature. For outdoor temperatures down to–20 F, it maintains condensing temperature at 100 F. Refer tothe accessory Motormaster installation instructions for moreinformation.CAPACITY CONTROL, COOLING — The cooling capaci-ty staging tables are shown in Tables 42 and 43.Table 42 — Cooling Capacity Staging Table, CVUnits with 2 CompressorsNOTE: On CV units that require additional unloading, add suctionpressure unloaders to Compressor 1 only.Table 43 — Cooling Capacity Staging Table VAVUnits with 2 Compressors and 2 Unloaders**40 ton units have only one unloader.It is often desirable to use a variable air volume (VAV) unitin a variable volume and temperature (VVT) control systembecause of the greater unloading capability. A VAV unit (withsoftware version 4.0 and later) can easily be configured in thefield to run off of either space thermostat (VVT® relay pack)input or a space sensor. When configured in this manner, theunit control will turn on compressors based upon load in thespace. If the supply-air falls below predefined limits, the con-trol will unload the compressor in order to maintain the mini-mum supply-air limit. If unloading is not successful in main-taining the minimum supply-air temperature (SAT), then thecompressors will be turned off. An alarm will be issued whenthe compressors are turned off.A VAV unit configured to run off thermostat input or aspace sensor will have the capability for two stages of heating,however, modification to the control wiring will be required tomake this available. The Variable Frequency Drive (VFD) forthe supply fan will still be active, varying the supply air fanspeed to maintain supply duct pressure.Upon a call for Y1 (or Y2_SPT) cooling, the compressor 1will start after appropriate Time Guard® functions. Thirty sec-onds after the SAT drops below the “SAT1TRIP” the compres-sor will be unloaded. The unloading sequence will be asfollows:The “Y1 Low SAT Limit” has an adjustable range from50 F to 65 F, with a factory setting of 53 F. If the temperature ofthe SAT rise above the “Y1 Low SAT Limit” plus 2° F, thecompressor will be loaded in the reverse order in which it wasunloaded following the pre-described time guards. There willbe a 90-second time guard between any change in unloadedstate, and the normal 5-minute time guard for change in com-pressor On/Off state.If compressor no. 1 is forced off due to “Y1 LOW SATLimit” an alert will be issued. If economizer is suitable, theeconomizer mode will remain active. The alert will be clearedafter the 5-minute time guard has expired and the compressor isrestarted. With Y1 (or Y1_SPT) input, only compressor no. 1can be running.Upon a call for Y1 (or Y1_SPT) and Y2 (or Y2_SPT) cool-ing both compressor no. 1 and 2 will start after appropriate timeguards. Thirty seconds after SAT drops below the “Y2 LowSAT Limit” the compressor will be unloaded. The unloadingsequence will be as follows:The “Y2 Low SAT Limit” has an adjustable range from45 F to 55 F, with a factory default setting of 48 F. If the tem-perature of the SAT rise above the “Y2 Low SAT Limit” plus2° F, the compressor will be loaded in the reverse order inwhich it was unloaded following the pre-described Time Guardfunctions. There will be a 90-second time guard between anychange in unloaded state, and the normal 5-minute time guardfor change in compressor On/Off state.DEVICE PRESSURIZATION SMOKE PURGE EVACUATION FIRE SHUTDOWNEconomizer 100% 100% 100% 0%Indoor Fan/VFD ON ON OFF OFFPower Exhaust (all outputs) OFF ON ON OFFHeat Stages OFF OFF OFF OFFCool Stages OFF OFF OFF OFFHIR ON ON OFF OFFHIR — Heat Interlock RelayVFD — Variable Frequency DriveStages0 1Economizer 2 3Compressor 1 off off on onCompressor 2 off off off onSTAGES0 1 2 3 4 5 6Compressor 1 off on on on on on onUnloader 1 off on on off on on offUnloader 2 off on off off on off offCompressor 2 off off off off on on onCompressor no. 1 On, Full Load Unloader no. 1 and no. 2 OffCompressor no. 1 On, 2/3 Load Unloader no. 1 Off, Unloader no. 2 OnCompressor no. 1 On, 1/3 Load Unloader no. 1 and no. 2 OnCompressor no. 1 Off Unloader no. 1 and no. 2 OffCompressor no. 1On, Full LoadUnloader no. 1 and no. 2 Off Compressor no. 2 OnCompressor no. 1On, 2 /3 LoadUnloader no. 1 Off,Unloader no. 2 OnCompressor no. 2 OnCompressor no. 1On, 1 /3 LoadUnloader no. 1 and no. 2 On Compressor no. 2 OnCompressor no. 1On, Full LoadUnloader no. 1 and no. 2 Off Compressor no. 2 OffCompressor no. 1On, 2 /3 LoadUnloader no. 1 Off,Unloader no. 2 OnCompressor no. 2 OffCompressor no. 1On, 1 /3 LoadUnloader no. 1 and no. 2 On Compressor no. 2 OffCompressor no. 1 Off Unloader no. 1 and no. 2 Off Compressor no. 2 Off