Honeywell W7750A Cascade Control of Modulating COOLING/HEATING, Series 60 Modulating Control

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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

cooling control algorithm compares the current space temperature to the EffectiveHeatSetPt, and calculates a PID error signal. This error signal causes the heating stage outputs to be cycled, as required, to drive the space temperature back to the Setpoint. Fig. 50 illustrates the relationship between PID error and staged output activity.

As the error signal increases, the space temperature gets further away from the setpoint, or is remaining below the setpoint as time elapses, additional stages of heating are energized until, if PID error reaches 100 percent, all configured stages are on.

The PID control algorithm used to control staged heating is anticipator-driven, and is similar to the algorithm used in the T7300 commercial thermostat. All staging events are subject to a minimum interstage time delay, that is based on the cycles per hour user setting (HeatCycHr). The minimum interstage time delay ranges from 90 seconds (at 12 cycles per hour) to eight minutes (at two cycles per hour). See Table

17.The user has the option to disable the minimum run timer for heating (DisMinHtTimer). If the minimum run timer is disabled, the interstage time delay is fixed at 20 seconds. The cycling rate is separately selectable for heating and cooling between two and 12 cycles per hour (cph).

Setpoints for the PID gains allow for unit-by-unit adjustment of the control loop, if required; however, any change from the default values should be minimal.

CASCADE CONTROL OF MODULATING COOLING/HEATING

The Excel 10 W7750 Controller supports modulating cooling and heating valves. These valves can be controlled directly from the space temperature (like the staged control) or, if the CascCtrl flag is set, they are modulated to maintain the discharge air temperature at its setpoint. The discharge air setpoint is calculated based on the space temperature deviation from the space setpoint. This is commonly called cascade control. In the W7750 Controller, cascade control is available for use with PWM (W7750B,C only) and Series 60 modulating heating and cooling, but not for use with staged heating/cooling.

Setpoints for the PID gains and for the control band allow for unit-by-unit adjustment of the control loops, if required; however, any change from the default values should be minimal. Also, the W7750 Controller uses an adaptive algorithm (patent pending) to continuously assess the validity of the calculated discharge setpoint, and adjust it, as needed, to ensure precise, accurate control.

SERIES 60 MODULATING CONTROL

Series 60 Control is also commonly referred to as Floating Control. The Excel 10 W7750A,B,C Controllers can drive Series 60 type actuators to control a modulating cooling valve, a heating valve, and economizer dampers. When floating control is used, the full-stroke motor drive time of the actuator must be entered into the configuration parameter CoolMtrSpd (for cooling), HeatMtrSpd (for heating), or EconMtrSpd (for the economizer dampers).

PULSE WIDTH MODULATING (PWM) CONTROL

The Excel 10 W7750B,C Controllers can drive a PWM-type actuator to control a modulating cooling valve, a heating valve, and economizer dampers. PWM control positions the

actuator based on the length, in seconds, of the pulse from the digital output. The controller outputs a pulse whose length consists of two parts, a minimum and a maximum. The minimum pulse time represents the analog value of zero percent (also indicates a signal presence) and the maximum pulse length that represents an analog value of 100 percent. If the analog value is greater than zero percent, an additional time is added to the minimum pulse time. The length of time added is directly proportional to the magnitude of the analog value. If PWM control is used, the configuration parameters for the PWM operation must be specified. These are PwmPeriod, PwmZeroScale, and PwmFullScale. These three parameters are shared by all configured PWM outputs; this means the heating, cooling, and economizer actuators must be configured to accept the same style of PWM signal.

Example: To find the pulse width of a valve actuator (for example stroke mid position - 50 percent) with the PwmZeroScale = 0.1 seconds, PwmFullScale = 25.5 seconds, and the PwmPeriod = 25.6 seconds. There are 256 increments available, so the number of increments required for 50 percent would be (0.5 X 256) or 128. The time for each increment for this industry standard pulse time is 0.1 seconds. The pulse width is the minimum time (0.1 second) + the number of increments (128 times the (0.1 second) plus 0. 1) =

12.9seconds. The W7750B,C Controllers would command the valve output on for 12.9 seconds for the PwmPeriod of

25.6seconds to maintain the valve position at 50 percent.

OUTDOOR AIR LOCKOUT OF HEATING/COOLING

A mechanism is provided in the W7750 to disable the heating equipment if the outdoor air temperature rises above the OaTempHtLkOut setpoint. Similarly, the cooling equipment is disabled if the outdoor air temperature falls below the OaTempClLkOut setpoint. The algorithm supplies a fixed 2° F (1.1° C) hysteresis with the lock-out control to prevent short cycling of the equipment.

ECONOMIZER DAMPER CONTROL

A mixed-air economizer damper package can be controlled to assist mechanical cooling in maintaining the discharge air at setpoint. Therefore, if modulating economizer damper control is desired, a discharge air temperature sensor is required. If the outdoor air is not currently suitable for cooling use (see the Economizer Enable/Disable Control section), the outdoor air damper is held at the user-settable minimum position (EconMinPos) for ventilation purposes.

Because the outdoor air can be used to supplement mechanical cooling, the economizer operates as if it were the first stage of cooling. So, if the outdoor air is suitable for cooling use, the mechanical cooling (either staged or modulating) is held off until the economizer has reached its fully open position. Then, if the discharge temperature continues to be above setpoint, the mechanical cooling is allowed to come on. If the outdoor air is not suitable for cooling use, the economizer is set to its minimum position, and mechanical cooling is allowed to come on immediately.

When the controller is in the Heat mode, the economizer is held at the minimum position setting (EconMinPos). The minimum position setting is only used during Occupied mode operation. When in Standby or Unoccupied modes, the outdoor air dampers are allowed to fully close if there is no call for cooling, or if the outside air is not suitable for cooling use.

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Contents Excel Appendices General Considerations W7750 Controllers72-2958 74-2958 List of Figures74-2958 Setpoint ramping parameters with ramp rate calculationList of Tables Typical system overview Description of DevicesControl Provided Control ApplicationOrganization of Manual Products CoveredApplicable Literature Form No TitleAgency Listings Product NamesAbbreviations and Definitions Controllers ConstructionDI-1 W7750APower Performance SpecificationsSpecial Note for the W7750B,C Unit CPU Specified Space Temperature Sensing RangeMemory Capacity Excel 10 W7750C Constant Volume AHU Controller Jack Lonmark Functional Profile DIN rail adaptersAnalog Inputs Inputs/OutputsTriac Outputs on the W7750B,C Models only Digital InputsDigital Outputs Duct Sensor Wall ModulesT7770A1006 T7770CT7560A,B construction in in. mm General ConfigurationsConfiguration Options Summary For W7750A,B,C Controllers Staged HEATING/COOLING Control Allowable Heating and Cooling Equipment ConfigurationsHeat Pump Control Modulating HEATING/COOLING ControlPneumatic Actuator Control Economizer ControlWindow Open/Closed Digital Input Occupancy SensorWall Module Options MIXED-OUTPUT-TYPE ControlDirty Filter Monitor Modes of OperationIndoor Air Quality IAQ Override Smoke ControlDisabled OFF ModeNot AssignedPlan the System OverviewDetermine Other Bus Devices Required Step No DescriptionLonworks Bus Layout Lay Out Communications and Power WiringExcel VAV Cvahu Power Budget Calculation Example Power WiringDeviceVA Information Obtained from ML6161A/B Damper Actuator, 35 lb-in R8242A Contactor VA Ratings For Transformer Sizing Device DescriptionML7984B PWM Valve Actuator Line LossNema class 2 transformer voltage output limits Power wiring details for one Excel 10 per TransformerGeneral Considerations Prepare Wiring DiagramsW7750 Controllers Terminal Terminal Number Description Factory Default Digital OutputsConstant Volume AHU Controller ML6161 Floating Actuator COM CCW Load Controller Power Heat Wall Economizer Damper PWM Actuator Power Signal W7750C Constant Pneumatic transducer to W7750B,C Shown, see triangle note Lonworks Bus Termination ModuleBrown Orange Order Equipment Lonworks Bus termination wiring optionsHoneywell Logo T7770D1018 T7770 and T7560 Wall ModulesSensor with Bypass/LED and Lonworks Jack Accessories Accessories SensorsEchelon Based Components and Parts Troubleshooting Configure ControllersTroubleshooting Excel 10 Controllers and Wall Modules CablingExcel 10 Alarms AlarmsResistance Value ohms W7750 Controller Status LED Broadcasting the Service MessageSetting the Pid Parameters Appendix A. Using E-Vision to Commission a W7750 ControllerT7770C,D Wall Module Bypass Pushbutton and Override LED Sensor CalibrationAppendix B. Sequences of Operation Common Operations Heating Room Temperature Sensor RmTempEconomizer IAQ OptionRemote Setpoint RmtStptPot Bypass Mode StatusOvrd and StatusLedSetpoint Limits LoSetptLim and HiSetptLim BypassTimeOccupancy Mode and Manual Override Arbitration Continuous Unoccupied ModeNot Assigned Bypass OccupiedTime Clock OccTimeClock Recovery Ramping for Heat Pump SystemsSchedule Master SchedMaster Setpoint RampingSmoke Control Window Sensor StatusWndwFAN Operation Demand Limit Control DLCSee for a diagram of a typical W7750 Unit Temperature Control OperationsDirty Filter Monitor ONE Stage Staged Cooling ControlTWO Stages Three StagesSeries 60 Modulating Control Cascade Control of Modulating COOLING/HEATINGPulse Width Modulating PWM Control Outdoor AIR Lockout of HEATING/COOLINGIndoor AIR Quality IAQ Override Economizer ENABLE/DISABLE ControlFreeze Stat Discharge AIR LOW Limit ControlControl Parameters Address Input Output Points AddressEnergy Management Points Address Status Points AddressMappable User Addresses and Table Number Air Flow Relative TemperatureCO2 Concentration EnthalpyPlaced in manual mode through a menu Application reset therefore, these points canValid states and the corresponding Enumerated values are shownInput/Output Points DefaultNvName Field Name CommentsOccsensor Shcedmasterin NciIoSelect DigitalIn1255 NciIoSelect DigitalIn2 Occsensor UnuseddiCOOLSTAGE2 COOLSTAGE1COOLSTAGE3 COOLSTAGE4Siinvalid SixtyfiftyFalse PPM SiinvalidTrue Position when poor indoor air quality is detected EconEnSw NvoIO EconEnableInStatusDI3 NvoIO UbDigitalIn OccSensr NvoIONvName Default CommentsControl Parameters MaxClRamp NciAux1SetPt UbMaxClRampS0 Degrees F/Hr OdEnthalpyEnableMinClRamp NciAux1SetPt UbMinClRampS0 Degrees F/Hr MaxClRamp, OdTempMaxClRamp,PPM GainCoolProp NciAux2SetPt UbKpCoolS2 Degrees F Degrees C Discharge air temperature cascade control loopGain for the cooling control loop GainHeatProp NciAux2SetPt UbKpHeatS2 Degrees F Degrees CEnergy Management Points NviFree1 Value Refer to WSHPEnable.valueAuxiliary functions. nviFree1 controls the FREE1OUT Network variable input failsDestTimeClk NviTimeClk State NviTimeClk ValueRefer to nviTimeClk.value 255 SrcTimeClkCt NvoTimeClk ValueStatus Points Bit Offset = SensorFailAlrm Alarmbit1Bit Offset = FrostProtectAlrm Bit Offset = InvalidSetPtAlrmNodedisabled NoalarmSmokealarm UpdateallfieldsStartupwait DisabledmodeHeat CoolAir flow switch is configured StatusEconEn NvoData1 EconEnableNciAux1SetPts.ubOdEnthalpyEnableS2 StatusManOcc NvoData1 NetManOccAuxiliary heating stages are turned on HeatStgsOn NvoData1 HeatStagesOnCoolStgsOn NvoData1 CoolStagesOn For both heating or coolingNciConfig.SmokeControl Is 1, the algorithm controls as per the settings foundController mode is switched to Freezeprotect MonitorSw NvoData1 MonSwitchTempcontrolptfield BypasstimerfieldSpacetempfield DischargetempfieldUbinvalid SpaceTempError StatusError NvoError Errorbit0NvoError Errorbit0 Bit Offset = Temperature SetPtError NvoError Errorbit0Bit Offset = RtnEnthalpyError NvoError Errorbit1 NvoError Errorbit1Are disabled as if the sensor was not configured Bit Offset = SpaceCO2Error NvoError Errorbit1Bit Offset = NvDlcShedError NvoError Errorbit2 Bit Offset = NvWindowError NvoError Errorbit2Bit Offset = NvTodEventError NvoError Errorbit3 Bit Offset = NvByPassError NvoError Errorbit3Cfgexternal CfglocalCfgnul Calibration PointsConfiguration Parameters False True DisMinClTime NciConfig DisableCoolMinTime DisMinHtTime NciConfig DisableHeatMinTimeCascCntrl NciConfig CascadeControl UseRaTempCtl NciConfigOffset Absolutemiddle Last NETNone Normal BypassonlyLonmark /Open System Points Hvacheat HvacautoHvacmrngwrmup Hvacprecool Hvaccool Hvacnightpurge Hvacnul HvacoffDestRmTemp NviSpaceTemp Degrees F 74-2958 100SNVTtempp 14 to SrcRmTemp NvoSpaceTemp Degrees FHvacmrngwrmup Hvacauto HvacnulHvactest Alarmnotifydisabled 103 NvoStatus Inalarm NvoStatus Electricalfault255 Not configured 74-2958 NvoStatus UnabletomeasureSwon Corresponding economizer function is not enabled because On other nodes. If the economizer function is configured bySrcEconEnable NvoEcon State SrcEconEnCt NvoEcon ValueDirect Access And Special Points OFF Data Share Points =using One-to-Many and not using points Approximate Memory Size Estimating Procedure= including mapped points and others for Mapped points = number of mapped points per ExcelResistance Sensors Sensor Resistance Versus Temperature Resistance OhmsSensor Type Sensor UseDirect Setpoint Temperature Offset Setpoint TemperatureT7770B,C 10K ohm setpoint potentiometer Relative Above and Below Setpoint Resistance OhmsSensor Voltage Versus Humidity Humidity Percentage Voltage/Current SensorsSensor Voltage Versus Humidity Relative Humidity Percentage 113 74-2958 Sensor Current Versus Enthalpy volts Enthalpy mA74-2958 114 T7242 or equivalentMAmAmAmA AmA mA mA Sensor Voltage Versus Input Voltage To A/D Voltage to A/D Pressure Inw kPa Sensor Voltage Vdc Sensor Voltage Vdc Versus Pressure InwInw 50.0.13
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