Carrier WEATHERMASTER 48/50Z030-105 Operation And Service Manual

Also see for 48/50Z030-105: Installation instructions

Contents

Carrier WEATHERMASTER 48/50Z030-105 Operation And Service Manual Manual pdf 69 page image

69The economizer’s reported and commanded positionsare also viewable, as well as outside air temperature, relativehumidity, enthalpy and dew point temperature.The following information can be found under the LocalDisplay Mode Run Status→ECON. See Table 57.Economizer Control Point Determination Logic — Once theeconomizer is allowed to provide free cooling, the economizermust determine exactly what set point it should try to maintain.The set point the economizer attempts to maintain when “freecooling” is located at Run Status→VIEW→EC.C.P. This isthe economizer control point.The control selects set points differently, based on thecontrol type of the unit. This control type can be found atConfiguration→UNIT→C.TYP. There are 6 types of control.C.TYP = 1 VAV-RATC.TYP = 2 VAV-SPTC.TYP = 3 TSTAT Multi-StagingC.TYP = 4 TSTAT 2 StageC.TYP = 5 SPT Multi-StagingC.TYP = 6 SPT 2 StageIf the economizer is not allowed to do free cooling, thenEC.C.P = 0.If the economizer is allowed to do free cooling and theUnoccupied Free Cooling Mode is ON, then EC.C.P =Setpoints→SASP + Inputs→RSET→SA.S.R.If the economizer is allowed to do free cooling and theDehumidification mode is ON, then EC.C.P = the CoolingControl Point (Run Status→VIEW→CL.C.P).If the C.TYP is either 4 or 6, and the unit is in a cool mode,then:If Stage = 0 EC.C.P = the Cooling Control Point (RunStatus→VIEW→CL.C.P)If Stage = 1 53.0 + economizer suction pressure resetIf Stage = 2 48.0 + economizer suction pressure resetNOTE: To check the current cooling stage go to Run Status→Cool→CUR.S.If the C.TYP is either 1,2,3 or 5, and the unit is in a coolmode, then EC.C.P = the Cooling Control Point (Run Status→VIEW→CL.C.P).Economizer Suction Pressure Reset for Two-StageCooling — If the unit’s control type is set to either 2-stage ther-mostat or 2-stage space temperature control, then there is nocooling control point. Stages 1 and 2 are brought on based ondemand, irrespective of the evaporator discharge temperature.In this case, the economizer monitors suction pressure andresets the economizer control point accordingly in order toprotect the unit from freezing. For those conditions when theeconomizer opens up fully but is not able to make set point, andthen a compressor comes on, it is conceivable that the coilmight freeze. This can be indirectly monitored by checking suc-tion pressure. Rather than fail a circuit, the control will attemptto protect the unit by resetting the economizer control pointuntil the suction pressure rises out of freezing conditions.If either circuit’s suction pressure drops to within 5 psigof the low suction pressure trip point, the control will startadding reset to the economizer control point if it is active. Itwill be possible to reset the control point upwards, 10 degrees(2 degrees per psig), between the low suction pressure trippoint of 48 psig and 5 psig above it. If this does not work, and ifthe suction pressure drops below the trip point, then the controlwill further reset the control point 1 degree every 15 secondsup to a maximum of 10 degrees. The resulting effect will be towarm up the mixed air entering the evaporator, thereby raisingthe suction pressure.Building Pressure Control — This control sequenceprovides control of the building pressure through the modulat-ing flow rate functions of one of the modulating power exhaustoptions or through management of the return fan option. Thisfunction also provides control of the constant volume 2-stagepower exhaust option. See below for available power exhaustoptions for each unit model.LEGENDTable 57 — Economizer Run Status TableUNIT CONSTANTVOLUME2-STAGEMODULATINGPOWEREXHAUSTS.O.VFD*HIGHCAPACITYPOWEREXHAUST†RETURN/EXHAUST†48ZG, 50ZG,Z2 X X S.O. NA NA48ZN, 50ZN,Z3 NA X S.O. NA NA48ZT,ZW50ZT,ZW,ZX,ZZ NA NA NA STD NA48Z6,Z850Z6,Z7,Z8,Z9 NA NA NA NA STDX — Available as Factory OptionS.O. — Available as Special OrderNA — Not Available on this UnitSTD — Standard Feature on this UnitITEM EXPANSION RANGE UNITS CCN POINT WRITE STATUSECN.P Economizer Act.Curr.Pos. 0-100 % ECONOPOSEC2.P Economzr 2 Act.Curr.Pos. 0-100 % ECON2POSECN.C Economizer Act.Cmd.Pos. 0-100 % ECONOCMD forcibleACTV Economizer Active ? YES/NO ECACTIVEDISA ECON DISABLING CONDITIONSUNV.1 Econ Act. Unavailable? YES/NO ECONUNAVUNV.2 Econ2 Act. Unavailable? YES/NO ECN2UNAVENTH Enth. Switch Read High ? YES/NO ENTHDBC DBC - OAT Lockout? YES/NO DBC_STATDEW DEW - OA Dewpt.Lockout? YES/NO DEW_STATDDBC DDBD- OAT > RAT Lockout? YES/NO DDBCSTATOAEC OAEC- OA Enth Lockout? YES/NO OAECSTATDEC DEC - Diff.Enth.Lockout? YES/NO DEC_STATEDT EDT Sensor Bad? YES/NO EDT_STATOAT OAT Sensor Bad ? YES/NO OAT_STATFORC Economizer Forced ? YES/NO ECONFORCSFON Supply Fan Not On 30s ? YES/NO SFONSTATCLOF Cool Mode Not In Effect? YES/NO COOL_OFFOAQL OAQ Lockout in Effect ? YES/NO OAQLOCKDHELD Econ Recovery Hold Off? YES/NO ECONHELDDH.DS Dehumid. Disabled Econ.? YES/NO DHDISABLO.AIR OUTSIDE AIR INFORMATIONOAT Outside Air Temperature dF OAT forcibleOA.RH Outside Air Rel. Humidity % OARH forcibleOA.E Outside Air Enthalpy OAEOA.D.T Outside Air Dewpoint Temp dF OADEWTMP*Single VFD controlling both fanmotors.†Single VFD controlling one fanmotor and staging of the secondfan motor.