Honeywell W7750A Indoor AIR Quality IAQ Override, Freeze Stat, Discharge AIR LOW Limit Control

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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

INDOOR AIR QUALITY (IAQ) OVERRIDE

The Excel 10 W7750 Controller supports an IAQ override feature that upon detection of poor air quality in the space, allows the economizer dampers to be opened above the standard minimum position setting to a value set in EconIAQPos. Two different methods of detecting poor air quality are supported, The first is by using an IAQ switch device connected to a digital input on the W7750 Controller, where a contact closure indicates poor air quality and initiates the IAQ override mode. The second, which is only available on the W7750B,C is through an analog input that connects to a CO2 Sensor (0 to 10V). The measured value of CO2 from this sensor (0 to 2000 ppm) is compared to the setpoint IAQSetpt. When the CO2 level is higher than the setpoint (800 PPM), the IAQ override is initiated. The IAQSetpt hysteresis is 50 PPM, IAQ override is deactivated at a CO2 level less than 750 PPM.

When the W7750 Controller is in the COOL mode during an IAQ override, it is possible for the heating outputs to be activated. This can occur if the outdoor air temperature is cold enough to cause the discharge air temperature to drop below the DaTempLoLim setpoint when the dampers open to the EconIAQPos position, and the IaqUseHeat flag is set. If this situation occurs, the heating is controlled to maintain the discharge air temperature at 1°F (0.65°C) above the DaTempLoLim setpoint.

FREEZE STAT

Upon receiving a contact closure, the W7750 control algorithm will close the outdoor air damper and open the hot water and chilled water valves (if available) to the full open position as a safety precaution. If manual-resetoperation is desired, the Freeze Stat device must provide the physical pushbutton, which the operator presses, to reset the system after a freeze condition has occurred.

DISCHARGE AIR LOW LIMIT CONTROL

If the discharge air temperature falls below the user-settable discharge air low limit setpoint (DaTempLoLim), an alarm is issued, and the outdoor air damper is driven below the minimum position setting until the discharge temperature is up to the low limit. If necessary, the damper can go completely closed even during Occupied mode operation. As the discharge temperature warms up, the economizer modulates open until the minimum position setting is reached. At this point, the low limit alarm is cleared.

ECONOMIZER ENABLE/DISABLE CONTROL

The W7750 Controller has inputs to determine if the outdoor air is suitable to augment cooling. The economizer dampers can be enabled/disabled for using outdoor air as the first stage of cooling based on one of ten allowable strategies:

1.Digital Input Enable/Disable—contact closure enables economizer.

2.Outdoor Temperature—when the outdoor temperature is less than OaEconEnTemp, then the outdoor air is suitable to augment cooling.

3.Outdoor Enthalpy, Type A—when the outdoor enthalpy meets the H205 type A requirements, the outdoor air is suitable to augment cooling.

4.Outdoor Enthalpy, Type B—when the outdoor enthalpy meets the H205 type B requirements, the outdoor air is suitable to augment cooling.

5.Outdoor Enthalpy, Type C—when the outdoor enthalpy meets the H205 type C requirements, the outdoor air is suitable to augment cooling.

6.Outdoor Enthalpy, Type D—when the outdoor enthalpy meets the H205 type D requirements, the outdoor air is suitable to augment cooling.

7.Differential Temperature—the difference between outdoor temperature and return air temperature is compared to DiffEconEnTemp to determine whether outdoor air or return air is more suitable for use to augment mechanical cooling.

8.Single Calculated Enthalpy—the calculated outdoor enthalpy in btu/lb is compared to the enthalpy setpoint (OaEnthEn) in btu/lb, and the outdoor temperature is compared to the outdoor temperature limit setpoint (OaEconEnTemp) for a high limit. The compared difference determines whether outdoor air is suitable for use to augment mechanical cooling.

9.Differential Enthalpy, Either Sensed or Calculated— the difference between outdoor enthalpy and return air enthalpy determines whether outdoor air or return air is more suitable to augment mechanical cooling. When enthalpy sensors are configured, they are used for comparing enthalpy. If no enthalpy sensors are available, then enthalpy is calculated using outdoor and return air humidity and temperature sensors. The switching differential is fixed at 1.0 mA for enthalpy sensors, and 0.25 btu/lb for calculated enthalpy.

NOTE: If no return temperature sensor is configured, space temperature is used to calculate return air enthalpy.

10.Network Enabled—the network input DestEconEnable controls the enabling and disabling of the economizer. When using the network input, select Econo Enable Type: No Economizer in E-Vision. The network input has priority over the other nine economizer control selections.

Appendix C. Complete List of Excel 10 W7750 Controller User Addresses.

See Table 18 for W7750 Controller User Address table numbers and point types.

The User Address Index following Table 18 lists the User Addresses alphabetically and gives the page number where the Address is located in each Table Number/Point Type.

After Table 18 there is an alphabetical list of Mappable User Addresses and Table Numbers. Following this is an alphabetical list of Failure Detect User Addresses and Table Numbers.

Table 18. Excel 10 W7750 Controller User

Address Point Types.

 

 

Table Number

Point Types

 

 

Table 20

Input/Output

 

 

Table 21

Control Parameters

 

 

Table 22

Energy Management Points

 

 

Table 23

Status Points

 

 

Table 24

Calibration Points

 

 

Table 25

Configuration Parameters

 

 

Table 26

LONMARK/Open System Points

 

 

Table 27

Direct Access and Special Manual Points

 

 

Table 28

Data Share Points

 

 

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Contents Excel 72-2958 General Considerations W7750 ControllersAppendices List of Figures 74-2958Setpoint ramping parameters with ramp rate calculation 74-2958List of Tables Description of Devices Typical system overviewControl Application Control ProvidedApplicable Literature Products CoveredOrganization of Manual Form No TitleProduct Names Agency ListingsAbbreviations and Definitions Construction ControllersW7750A DI-1Special Note for the W7750B,C Unit Performance SpecificationsPower Memory Capacity Specified Space Temperature Sensing RangeCPU Excel 10 W7750C Constant Volume AHU Controller Jack DIN rail adapters Lonmark Functional ProfileInputs/Outputs Analog InputsDigital Outputs Digital InputsTriac Outputs on the W7750B,C Models only T7770A1006 Wall ModulesDuct Sensor T7770CT7560A,B construction in in. mm Configurations GeneralConfiguration Options Summary For W7750A,B,C Controllers Heat Pump Control Allowable Heating and Cooling Equipment ConfigurationsStaged HEATING/COOLING Control Modulating HEATING/COOLING ControlEconomizer Control Pneumatic Actuator ControlWall Module Options Occupancy SensorWindow Open/Closed Digital Input MIXED-OUTPUT-TYPE ControlIndoor Air Quality IAQ Override Modes of OperationDirty Filter Monitor Smoke ControlNot OFF ModeDisabled AssignedDetermine Other Bus Devices Required OverviewPlan the System Step No DescriptionLay Out Communications and Power Wiring Lonworks Bus LayoutExcel VAV Cvahu DeviceVA Information Obtained from Power WiringPower Budget Calculation Example ML7984B PWM Valve Actuator VA Ratings For Transformer Sizing Device DescriptionML6161A/B Damper Actuator, 35 lb-in R8242A Contactor Line LossPower wiring details for one Excel 10 per Transformer Nema class 2 transformer voltage output limitsPrepare Wiring Diagrams General ConsiderationsW7750 Controllers Factory Default Digital Outputs Terminal Terminal Number DescriptionConstant Volume AHU Controller ML6161 Floating Actuator COM CCW Load Controller Power Heat Wall Economizer Damper PWM Actuator Power Signal W7750C Constant Lonworks Bus Termination Module Pneumatic transducer to W7750B,C Shown, see triangle noteBrown Orange Lonworks Bus termination wiring options Order EquipmentSensor with Bypass/LED and Lonworks Jack T7770 and T7560 Wall ModulesHoneywell Logo T7770D1018 Echelon Based Components and Parts Accessories SensorsAccessories Troubleshooting Excel 10 Controllers and Wall Modules Configure ControllersTroubleshooting CablingResistance Value ohms AlarmsExcel 10 Alarms Broadcasting the Service Message W7750 Controller Status LEDT7770C,D Wall Module Bypass Pushbutton and Override LED Appendix A. Using E-Vision to Commission a W7750 ControllerSetting the Pid Parameters Sensor CalibrationAppendix B. Sequences of Operation Common Operations Economizer Room Temperature Sensor RmTempHeating IAQ OptionSetpoint Limits LoSetptLim and HiSetptLim Bypass Mode StatusOvrd and StatusLedRemote Setpoint RmtStptPot BypassTimeNot Assigned Continuous Unoccupied ModeOccupancy Mode and Manual Override Arbitration Bypass OccupiedSchedule Master SchedMaster Recovery Ramping for Heat Pump SystemsTime Clock OccTimeClock Setpoint RampingFAN Operation Window Sensor StatusWndwSmoke Control Demand Limit Control DLCDirty Filter Monitor Temperature Control OperationsSee for a diagram of a typical W7750 Unit TWO Stages Staged Cooling ControlONE Stage Three StagesPulse Width Modulating PWM Control Cascade Control of Modulating COOLING/HEATINGSeries 60 Modulating Control Outdoor AIR Lockout of HEATING/COOLINGFreeze Stat Economizer ENABLE/DISABLE ControlIndoor AIR Quality IAQ Override Discharge AIR LOW Limit ControlEnergy Management Points Address Input Output Points AddressControl Parameters Address Status Points AddressMappable User Addresses and Table Number CO2 Concentration Relative TemperatureAir Flow EnthalpyValid states and the corresponding Application reset therefore, these points canPlaced in manual mode through a menu Enumerated values are shownNvName Field Name DefaultInput/Output Points Comments255 NciIoSelect DigitalIn2 NciIoSelect DigitalIn1Occsensor Shcedmasterin Occsensor UnuseddiCOOLSTAGE3 COOLSTAGE1COOLSTAGE2 COOLSTAGE4Sixtyfifty SiinvalidTrue PPM SiinvalidFalse StatusDI3 NvoIO UbDigitalIn EconEnSw NvoIO EconEnableInPosition when poor indoor air quality is detected OccSensr NvoIODefault Comments NvNameControl Parameters MinClRamp NciAux1SetPt UbMinClRampS0 Degrees F/Hr OdEnthalpyEnableMaxClRamp NciAux1SetPt UbMaxClRampS0 Degrees F/Hr MaxClRamp, OdTempMaxClRamp,PPM Gain for the cooling control loop Discharge air temperature cascade control loopGainCoolProp NciAux2SetPt UbKpCoolS2 Degrees F Degrees C GainHeatProp NciAux2SetPt UbKpHeatS2 Degrees F Degrees CEnergy Management Points Auxiliary functions. nviFree1 controls the FREE1OUT Refer to WSHPEnable.valueNviFree1 Value Network variable input failsRefer to nviTimeClk.value NviTimeClk ValueDestTimeClk NviTimeClk State 255 SrcTimeClkCt NvoTimeClk ValueStatus Points Bit Offset = FrostProtectAlrm Alarmbit1Bit Offset = SensorFailAlrm Bit Offset = InvalidSetPtAlrmSmokealarm NoalarmNodedisabled UpdateallfieldsHeat DisabledmodeStartupwait CoolNciAux1SetPts.ubOdEnthalpyEnableS2 StatusEconEn NvoData1 EconEnableAir flow switch is configured StatusManOcc NvoData1 NetManOccCoolStgsOn NvoData1 CoolStagesOn HeatStgsOn NvoData1 HeatStagesOnAuxiliary heating stages are turned on For both heating or coolingController mode is switched to Freezeprotect Is 1, the algorithm controls as per the settings foundNciConfig.SmokeControl MonitorSw NvoData1 MonSwitchSpacetempfield BypasstimerfieldTempcontrolptfield DischargetempfieldUbinvalid NvoError Errorbit0 StatusError NvoError Errorbit0SpaceTempError Bit Offset = Temperature SetPtError NvoError Errorbit0Are disabled as if the sensor was not configured NvoError Errorbit1Bit Offset = RtnEnthalpyError NvoError Errorbit1 Bit Offset = SpaceCO2Error NvoError Errorbit1Bit Offset = NvTodEventError NvoError Errorbit3 Bit Offset = NvWindowError NvoError Errorbit2Bit Offset = NvDlcShedError NvoError Errorbit2 Bit Offset = NvByPassError NvoError Errorbit3Cfgnul CfglocalCfgexternal Calibration PointsConfiguration Parameters False True CascCntrl NciConfig CascadeControl DisMinHtTime NciConfig DisableHeatMinTimeDisMinClTime NciConfig DisableCoolMinTime UseRaTempCtl NciConfigNone Normal Last NETOffset Absolutemiddle BypassonlyLonmark /Open System Points Hvacmrngwrmup Hvacprecool Hvaccool Hvacnightpurge Hvacnul HvacautoHvacheat HvacoffSNVTtempp 14 to 74-2958 100DestRmTemp NviSpaceTemp Degrees F SrcRmTemp NvoSpaceTemp Degrees FHvactest Hvacauto HvacnulHvacmrngwrmup Alarmnotifydisabled 255 Not configured 74-2958 NvoStatus Electricalfault103 NvoStatus Inalarm NvoStatus UnabletomeasureSwon SrcEconEnable NvoEcon State On other nodes. If the economizer function is configured byCorresponding economizer function is not enabled because SrcEconEnCt NvoEcon ValueDirect Access And Special Points OFF Data Share Points = including mapped points and others for Approximate Memory Size Estimating Procedure=using One-to-Many and not using points Mapped points = number of mapped points per ExcelSensor Type Sensor Resistance Versus Temperature Resistance OhmsResistance Sensors Sensor UseT7770B,C 10K ohm setpoint potentiometer Relative Offset Setpoint TemperatureDirect Setpoint Temperature Above and Below Setpoint Resistance OhmsSensor Voltage Versus Humidity Relative Humidity Percentage Voltage/Current SensorsSensor Voltage Versus Humidity Humidity Percentage Sensor Current Versus Enthalpy volts Enthalpy mA 113 74-2958MAmAmAmA AmA mA mA T7242 or equivalent74-2958 114 Sensor Voltage Versus Input Voltage To A/D Voltage to A/D Inw Sensor Voltage Vdc Versus Pressure InwPressure Inw kPa Sensor Voltage Vdc 50.0.13