McQuay MicroTech III RAH Operation And Maintenance Manual
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McQuay MicroTech III RAH Operation And Maintenance Manual

Microtech iii unit controller for applied rooftop and self-contained systems
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MicroTech
®
Rooftop and Self-Contained Systems
RAH, RCS, RDS, RDT, RFS, RPS, SWP, and SWT
© 2009 McQuay International
Operation and Maintenance Manual
III Unit Controller for Applied
OM 920-1
Group: Applied Systems
Part Number: OM 920-1
Date: October 2009

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  • Page 1 Operation and Maintenance Manual OM 920-1 MicroTech III Unit Controller for Applied ® Group: Applied Systems Part Number: OM 920-1 Rooftop and Self-Contained Systems Date: October 2009 RAH, RCS, RDS, RDT, RFS, RPS, SWP, and SWT © 2009 McQuay International...
  • Page 3 Contents Introduction .............. 4 LON/BACnetIP/BACnetMSTP Setup Menu ..50 Getting Started ........... 5 Alarm Delays Setup Menu ........ 50 Using the Keypad/Display ........6 Analog Input Status Menu......... 50 Passwords ............7 Universal I/O Status Menu ........ 51 Navigation Mode ..........8 Digital Input Status Menu........

  • Page 4: Introduction

    Operation of this equipment in a residential area is likely to cause harmful interference in which case the user is required to correct the interference at his own expense. McQuay International disclaims any liability resulting from any interference or for the correction thereof.

  • Page 5: Getting Started

    • DSP Setpoint • BSP Setpoint • Heat/Cool Changeover (Zone Setpoints) • DAT Clg Setpoint • DAT Htg Setpoint • Clg Enable (OAT/EWT lockout) • Htg Enable (OAT lockout) • Econo Enable (Changeover temp/Enthalpy switch) • Ventilation Limit/OA damper McQuay OM 920-1...

  • Page 6: Using The Keypad/Display

    PI loop parameters and time delays. Advanced Menus include the most advanced items such as “unit configuration” parameters and service related parameters. These generally do not needing changing or accessing unless there is a fundamental change to or a problem with the unit operation. McQuay OM 920-1...

  • Page 7: Passwords

    The default value for this password timer is 10 minutes. It is changeable from 3 to 30 minutes via the Timer Settings menu in the Extended Menus. McQuay OM 920-1...

  • Page 8: Navigation Mode

    The user may elect to initiate a rapid startup sequence at unit power up by setting the Rapid Start flag to Yes. When this flag is set to Yes, the Service Timer is set to 10 minutes whenever the power is reset to the controller. McQuay OM 920-1...

  • Page 9: Manual Control

    • High Return Temperature • High Discharge Temperature • Low Discharge Temperature • High Pressure - Circuit # 1 • High Pressure - Circuit # 2 • Low Pressure - Circuit # 1 • Low Pressure - Circuit # 2 McQuay OM 920-1...

  • Page 10: Keypad/Display Menu Structure

    Keypad/display menus are divided into 1) System Summary menu - password required. 2) Standard menu - password not required. 3) Extended Menu - higher level password required. 4) Advanced Menu - requires the highest level password. Figure 4: Keypad/Display Menu Structure McQuay OM 920-1...
  • Page 11 Keypad/Display Menu Structure McQuay OM 920-1...

  • Page 12: System Summary Menu

    Zone Clg Spt is a status only item which indicates the temperature in which the unit will go into the cooling mode of operation. Zone Htg Spt is a status only item which indicates the temperature in which the unit will go into the heating mode of operation. McQuay OM 920-1...
  • Page 13 EW Temp is a status only item that displays the current temperature reading from the unit mounted entering water temperature sensor. The sensor is standard on all water-cooled units. Rel Humidity is a status only item that displays the current relative humidity reading from the optional humidity sensor. McQuay OM 920-1...

  • Page 14: Standard Menus

    Standard Menu System Occupancy Temperatures Flow Summary SAF Spd Control RF/EF Spd Control Cooling Head Pressure Evap Condensing Economizer Min OA Damper Heating Energy Recovery Dehumidification Daily Schedule One Event Schedule Holiday Schedule Optimal Start Operating Hours McQuay OM 920-1...

  • Page 15: System Menu

    OffMan OffDehum Clg Capacity= 0-100% Htg Capacity= 0-100% Reheat Cap= 0-100% SAF Speed = 0-100% RF/EF Speed = 0-100% OAD/Econo Cap= 0-100% Rel Humidity= 0-100% Emerg Mode= Normal Normal Net App Mode= Auto HeatOnly CoolOnly FanOnly Auto McQuay OM 920-1...
  • Page 16 Net App Mode is a network adjustable item which indicates that the unit is set for network off, cooling only, heating only, fan only or auto heating/cooling operation via a network signal. This item has no affect on the unit operation unless the Ctrl Mode item is set to “Auto.” McQuay OM 920-1...

  • Page 17: Occupancy Menu

    UnoccSrc is a status only item which indicates the input source or function that is responsible for setting the Occupancy parameter to “Unocc.” Tnt Ovrd Time is an adjustable item which indicates the amount of time remaining for unit operation since tenant override operation was activated. McQuay OM 920-1...

  • Page 18: Temperature Menu

    The sensor is standard on all water-cooled units. MAT (SCU) is a status only item that displays the current temperature reading from the unit mounted mixed air temperature sensor. The sensor is standard on all Self Contained units. McQuay OM 920-1...

  • Page 19: Flow Summary Menu

    Ret/Exh Fan is a status only item which indicates whether or not the controller is commanding the unit RF/EF fan on. FanOp is a status only item which indicates whether this output (MCB DO10) is On or Off. McQuay OM 920-1...

  • Page 20: Supply Fan Speed Menu

    RF/EF CP Ctrl is an adjustable parameter used to select how the return/exhaust fans are to be controlled. The exhaust fans can be controlled by the building pressure or by a percentage of return/exhaust air fan speed from 25% to 100%. The speed option is typically used with a building automation system. McQuay OM 920-1...

  • Page 21: Cooling Menu

    Max Clg Spt @ is an adjustable item which sets the value of the sensor input, selected with the Cooling Reset parameter, at which the DAT cooling setpoint parameter is reset to the maximum DAT cooling setpoint value. McQuay OM 920-1...

  • Page 22: Head Pressure Menu

    Setpoint is an adjustable item that sets the refrigerant setpoint used for controlling the water regulating valve. The water-regulating valve is modulated to maintain the refrigerant pressure. Note – This section only applies to Self Contained units with a water regulating valve. McQuay OM 920-1...

  • Page 23: Evap Condensing Menu

    Dolphin System is an adjustable parameter that indicates to the controller whether or not a Dolphin water treatment method is being used. When set to “yes” the controller assures the sump pump is run every three days to reduce scaling. McQuay OM 920-1...

  • Page 24: Economizer Menu

    Min OA Pos is a status only item which indicates the current minimum position of the outdoor damper. This value does not go above a value called the Ventilation Limit and does not go below a value called the Demand Control Ventilation Limit. McQuay OM 920-1...
  • Page 25 Min Fan Diff is an adjustable item which sets a differential between the discharge and return fan capacities above which the minimum allowable Min OA Position begins to be reset upwards from the Demand Control Ventilation Limit toward the Ventilation Limit. McQuay OM 920-1...

  • Page 26: Heating Menu

    Unocc Htg Spt is an adjustable item which sets the zone temperature at which the unit starts up and provides unoccupied heating (night setback) during unoccupied periods. MWUSpt is an adjustable item which sets the heating setpoint to be used during morning warm up on a discharge temperature control unit. McQuay OM 920-1...

  • Page 27: Energy Recovery

    Min Exh T Diff is an adjustable item that sets a differential below the calculated potential energy recovery exhaust air frosting point. When the ER Exh T falls below the calculated McQuay OM 920-1...

  • Page 28: Dehumidification Menu

    The Reheat Setpoint equals the DAT Cooling Setpoint for DAT controlled units and will vary in between the minimum and maximum reheat setpoint for Zone Controlled units. Reheat Cap is a status only item that indicates the current reheat capacity value. McQuay OM 920-1...

  • Page 29: Daily Schedule Menu

    Des Htg OAT= 0°F -40-60°F Clg Rate= 0.4°F/min 0.0-1.0°F/min Clg OAT= 85°F -60-140°F Des Clg OAT= 95°F -60-140°F Enable is an adjustable item that turns on the optimal start feature. Setting the value to yes will activate this function. McQuay OM 920-1...

  • Page 30: Operating Hours Menu

    Comp #7 is a status item which gives the number of hours that compressor #7 has operated. Comp #8 is a status item which gives the number of hours that compressor #8 has operated. Heating is a status item which gives the number of hours that the heating mode has operated. McQuay OM 920-1...

  • Page 31: Extended Menus

    OAT Sensor is an adjustable item used to select whether or not the Outside Air Temperature sensor input will be used. Space Sensor is an adjustable item to indicate if a space sensor is connected to the unit controller. McQuay OM 920-1...

  • Page 32: Timer Settings Menu

    (waterside) or cooling operating state on unit with a water cooled condenser. This is to allow enough time for the water flow switch and the entering water temperature to be checked before the unit begins economizer or cooling operation. McQuay OM 920-1...

  • Page 33: Time/Date Menu

    Max Spd Chg is an adjustable item that sets the maximum value for a VFD speed increase or decrease. This speed change (either a positive or negative value) is added to the current fan speed whenever the duct static pressure is outside of the deadband, and a counter exceeds the sample time. McQuay OM 920-1...

  • Page 34: Return/Exhaust Fan Setup Menu

    5%). %). The outdoor air dampers must be open more that this value for prop exhaust fan operation. MinExhSAFCap is an adjustable item that sets the Minimum Exhaust SAF capacity (default 10%). The supply air fan speed must be higher than this value for prop exhaust fan operation. McQuay OM 920-1...

  • Page 35: Zone Temperature Setup Menu

    Htg PAT is an adjustable item which sets the “project ahead” used in the PI control function to vary the DAT Htg Spt in zone control applications. Max Htg Chg is an adjustable item that sets the maximum value for an increase or decrease of the DAT Htg Spt in zone control applications. McQuay OM 920-1...

  • Page 36: Compressor Setup Menu

    OAT Clg Lock value by more than this differential. Min EWT is an adjustable item that sets the minimum allowable entering water temperature. Mechanical Cooling is disabled when the entering water temperature sensor input falls below this setpoint McQuay OM 920-1...

  • Page 37: Head Pressure Setup Menu

    Clg DB an adjustable item which sets a dead band around the discharge cooling setpoint parameter. For example, if the discharge cooling setpoint parameter is set to 55ºF and the Clg Db parameter is set to 2ºF the dead band around the set point would be from 56.0ºF to 54.0ºF. McQuay OM 920-1...

  • Page 38: Economizer Setup Menu

    Max Inc Rate is an adjustable item that sets the maximum speed at which the OA damper opens after the recirculation mode if it is cold outdoors and the unit has a water coil. McQuay OM 920-1...

  • Page 39: Design Flow Setup Menu

    RH Lvl Pos is a status item which is used to calibrate the right-hand side (unit drive side) of the optional DesignFlow outdoor measuring apparatus. For details regarding calibration of the DesignFlow apparatus, refer to the applicable model-specific installation and maintenance manual McQuay OM 920-1...

  • Page 40: Heating Setup Menu

    Hold Period is an adjustable item used to set the amount of time that the gas heating valve remains at its calculated value on units equipped with 100% OA (default 240 seconds). This is to allow the temperature to approach equilibrium with the modulating gas heating valve at a fixed position. McQuay OM 920-1...

  • Page 41: Dehumidification Setup Menu

    Dehum Method is an adjustable item used to select whether dehumidification operation is based on relative humidity or dew point. Dehum Ctrl is an adjustable item used to select whether dehumidification as “always” allowed or only during “occupied” modes of operation. McQuay OM 920-1...

  • Page 42: Alarm Out Configuration Setup Menu

    • Faults - Fast Blink • Problems - Slow Blink • Warnings - Off A user could eliminate any signal of a particular group of alarms through this output by selecting On for that alarm group in the keypad/display. McQuay OM 920-1...

  • Page 43: Alarm Limits Setup Menu

    OAD OpCl= Close Close Open Comp 1 = Comp 2 = Comp 3 = Comp 4 = Comp 5 = Comp 6 = Comp 7 = Comp 8 = CFan Outpt 1= CFan Outpt 2= CFan Outpt 3= McQuay OM 920-1...
  • Page 44 RF/EF Spd Cmd is an adjustable item for units with VFD on the return/exhaust fans that set the speed of the return/exhaust fan. OAD/Econo is an adjustable item which is used to set the economizer damper position. McQuay OM 920-1...
  • Page 45 Htg Stg 6 is an adjustable item that turns on the sixth stage of electric heat. Reheat Valve is an adjustable item used to manually drive the reheat valve open and closed. Reheat Stage is an adjustable item that turns on the staged reheat output. McQuay OM 920-1...

  • Page 46: Active Alarm Menu

    Note – Once an alarm is cleared there will be two entries in the Alarm Log. A (+) sign will be shown next to the entry added when the alarm became active and a (-) sign will be shown next to the entry added when the alarm has been cleared. McQuay OM 920-1...

  • Page 47: Advanced Menus

    0 = Rooftop (RTU) • • 1 = Self-Contained (SCU) Control Type 0 = Zone Control • • 1 = DAT Control Cooling Type 0 = None • • 1 = Compressorized Clg 2 = Chilled Water 3 = F&BP McQuay OM 920-1...
  • Page 48 Supply Fan Type 0=Constant Volume • • 1=VFD/ABB 2=VFD/Graham 3=VFD/McQ21 4=VFD/McQ31 5=VFD/McQ61 Return Fan Type 0=CAV • 1=RF_EF VFD/ABB 2=RF_EF VFD/Graham 3=RF_EF VFD/McQ21 4=RF_EF VFD/McQ31 5=RF_EF VFD/McQ61 6=PrpEx VFD/ABB 7=PrpEx VFD/Graham 8=PrpEx VFD/McQ21 9=PrpEx VFD/McQ31 A=PrpEx VFD/McQ61 B=None McQuay OM 920-1...

  • Page 49: Save/Restore Menu

    The Save/Restore menu can be used to save or restore the user configured parameters as well as reset the controller back to the factory default parameters. Table 44: Save/Restore Menu Menu Display Name Item Display Name Default Setting Range Password Level Save/Restore Save Params= No/Yes Rstr Params= No/Yes Rstr Factory= No/Yes McQuay OM 920-1...

  • Page 50: Lon/Bacnetip/Bacnetmstp Setup Menu

    This would translate to a temperature of 53.5°F. Table 46: Analog Input Status Menu Menu Display Name Item Display Name Default Setting Range Password Level Analog Input Status MCB-AI1= 0-99999999 MCB AI2= 0-99999999 MCB AI3= 0-99999999 McQuay OM 920-1...

  • Page 51: Universal I/O Status Menu

    0-9999999 EMB X5= 0-9999999 EMB X6= 0-9999999 EMB X7= 0-9999999 EMB X8= 0-9999999 EMC X1= 0-9999999 EMC X2= 0-9999999 EMC X3= 0-9999999 EMC X4= 0-9999999 EMC X5= 0-9999999 EMC X6= 0-9999999 EMC X7= 0-9999999 EMC X8= 0-9999999 McQuay OM 920-1...

  • Page 52: Digital Input Status Menu

    Password Level Digital Output Status MCB DO1= MCB DO2= MCB DO3= MCB DO4= MCB DO5= MCB DO6= MCB DO7= MCB DO8= MCB DO9= MCB DO10= EMA DO1= EMA DO2= EMA DO3= EMA DO4= EMA DO5= EMA DO6= McQuay OM 920-1...
  • Page 53 Table 49: Digital Output Status Menu Menu Display Name Item Display Name Default Setting Range Password Level Digital Output Status EMB DO1= EMB DO2= EMB DO3= EMB DO4= EMB DO5= EMB DO6= EMC DO1= EMC DO2= EMC-DO3= EMC-DO4= EMC DO5= EMC DO6= McQuay OM 920-1...

  • Page 54: Adv Setup Settings Menu

    3rdWeek 4thWeek 5thWeek DLS Active= UTC Diff= Gas Derate V= 0-10V Max Purge Hld 10-180s Rapid Start= Rapid Start Tm= 10min 0-20min RH Sens Type VDC/mA RH Min Signal 0.0V 0.0-20V/mA RH Max Signal 10.0V 0.0-20V/mA EMGOffAuto= McQuay OM 920-1...

  • Page 55: Adv Status Parameters Menu

    -50.0-150.0°F CldStrtMinOA= 0-100% SF MB Status= Fault/OK RF MB Status= Fault/OK ER MB Status= Fault/OK EC MB Status= Fault/OK SAFVFD Ex Flt= Fault/OK RxFVFD Ex Flt= Fault/OK ER VFD Ex Flt= Fault/OK EC VFD Ex Flt= Fault/OK McQuay OM 920-1...

  • Page 56: Alarms

    If the pressure drop across the filter section in the unit exceeds the setting of the differential pressure switch the Dirty Filter warning occurs. When the Dirty Filter warning occurs, unit operation is not affected. The Dirty Filter warning must be manually cleared through the unit keypad or via a network signal. McQuay OM 920-1...

  • Page 57: Problems

    High Pressure - Circuit 1, 2, 3, 4, 5, 6 This alarm occurs on units equipped with compressorized cooling only. If the high pressure switch opens indicating a high refrigerant pressure situation, the High Pressure Circuit 1, 2, 3,4,5,6 problems occurs. McQuay OM 920-1...
  • Page 58 • Cooling Reset and Heating Reset revert to none if they are set to OAT • Economizer is locked out due to high OAT When the alarm condition is no longer present, the OAT Sensor problem automatically clears. McQuay OM 920-1...
  • Page 59 The Fan Fail alarm is initiated if these conditions are encountered three times between 2:00 am of one day and 2:00 am the following day. If the Fan Fail alarm is then cleared, the process may be repeated so that the unit may be shut down up to three more times. McQuay OM 920-1...

  • Page 60: Faults

    Sensor Alarm Delay (Default= 30 seconds), the Discharge Air Sensor fault occurs. When the Discharge Air Sensor fault occurs, the unit is shut down. It remains shut down until the Discharge Air Sensor fault is manually cleared through the unit keypad or via a network signal. McQuay OM 920-1...
  • Page 61 10-minute timer resets. This continues until the fault is manually cleared through the keypad or via a network signal. Note – Water valves remain open and Pump output remains on for 10 minutes after alarm conditions disappear. McQuay OM 920-1...

  • Page 62: Operator's Guide

    3 minutes (adjustable) before finally going into the Fan Only state of operation. Then, based on sensor inputs it will go into any of the 4 remaining states of operation - heating, cooling, economizer, or minimum discharge air heating. McQuay OM 920-1...

  • Page 63: Determining Unit State

    The unit operating state is Off Network when the control mode is set to Auto via the keypad System menu, and the network Net App Mode is set to off. OFF Alarm The unit operating state is Off Alarm when an active alarm of the “fault” type has the unit shutdown. McQuay OM 920-1...

  • Page 64: Start Up Operating State

    Note – On VAV or CAV discharge control units, the DAT cooling setpoint parameter in the Cooling menu acts as the minimum discharge temperature limit. On CAV zone control units the Min DAT Limit parameter in the Heating menu acts as the minimum discharge temperature limit. McQuay OM 920-1...

  • Page 65: Heating

    • The control temperature rises above the zone cooling setpoint by more that ½ the zone cooling deadband • The discharge air temperature is greater than the DAT cooling setpoint by more than ½ the DAT cooling deadband • Post heat operation is complete • Economizer operation is disabled McQuay OM 920-1...

  • Page 66: Determining Unit Status

    Heating operation is disabled (Heating Status is “Off Man”). Fan Only When the Control Mode is set to “Fan Only,” the fans are allowed to operate but cooling and heating operation is disabled (Cooling Status and Heating Status are “Off Man”). McQuay OM 920-1...

  • Page 67: Determining Cooling Status

    Off Network Control mode is set via the keypad to auto and cooling is disabled via a network command. Off Manual Control mode is set to Fan Only or Heat Only via the System menu. McQuay OM 920-1...

  • Page 68: Determining Heat Status

    EWT differential or the unit is configured for airside economizer, the enthalpy switch input indicates low enthalpy, and the outdoor air temperature (OAT) is low enough for operation None Economizer capability is not provided. McQuay OM 920-1...

  • Page 69: Determining Cooling Capacity

    The current RF/EF Capacity can be view via the following path: Standard Menus/System/RF/EF Capacity. 0-100% of VFD maximum speed is indicated if the unit is equipped with a return or exhaust fan VFD. 100% is indicated if the return/exhaust fan is constant volume and is running. McQuay OM 920-1...

  • Page 70: Determining Outside Air Damper Position

    (Cooling Status and Heating Status are “Off Net”). Auto When the Net App Mode is set to “Auto” heating and cooling operation are allowed to operate as required to maintain the heating and cooling set points. McQuay OM 920-1...

  • Page 71: Determining Occupancy Status

    The TOTime entry on the keypad can also be manually set to a non-zero value. In this case the value begins timing down from the edited value. Tenant Override Operation may be terminated by manually setting the Tenant Override parameter on the keypad to zero or by disabling the unit. McQuay OM 920-1...

  • Page 72: Determining Occupancy Mode

    Override Timer is set to a non-zero value, the unit starts and runs in the tenant override mode regardless of any scheduling features. The unit stops when the timer expires. The Tenant Override Timer can be set from 0-300 minutes. McQuay OM 920-1...

  • Page 73: Unoccupied Operation

    These are followed by a section describing the optimal start function which can be use with internal scheduling and network scheduling. This is followed by two sections that describe the external time scheduling and network time scheduling functions. McQuay OM 920-1...
  • Page 74 101 and 102 on the unit field terminal block TB2. In this case, all internal daily schedules should be set to “00:00-00:00” (default setting). McQuay OM 920-1...

  • Page 75: Temperature Control Configurations

    ½ the deadband (point D), at which point the unit returns or fan only (or Min DAT) operating state. Figure 7: Heat/Cool Changeover Cooling Enabled Cooling SPT Fan Only Heating SPT Heating Enabled Time McQuay OM 920-1...
  • Page 76 0.5 degrees through the wall mounted sensor, the Zone Heating Set point is raised or lowered the same amount so that the difference between the Cooling and Heating set points do not change. McQuay OM 920-1...
  • Page 77 When Optimum Start is used ZeroOATime is set equal to the time to occupancy when the unit starts so that the OA dampers will open at occupancy time. The parameter is adjustable via the following path: Extended Menus/Timer Settings/Zero OA Time. McQuay OM 920-1...

  • Page 78: Dehumidification

    Cooling state. For units with compressors, the number of cooling stages is reduced by one and control reverts to normal control when dehumidification is terminated in the Cooling state. Another compressor stage change could then occur after one Cooling Stage Time has elapsed McQuay OM 920-1...
  • Page 79 Extended Menus/Dehum Setup/Min Rheat Spt or Max Rheat Spt. Staged HGRH Control In the Cooling and Fan Only states, a staged output is turned on and off to control the HGRH valve to maintain the Discharge Air Temperature at the Dehumidification Reheat Setpoint. McQuay OM 920-1...

  • Page 80: Energy Recovery

    VFD controlling the speed of the Enthalpy Wheel. The Enthalpy Wheel is turned off when any of the following is true • The Exhaust Fan is off OR • The OA Damper Position is driven above the Minimum OA Damper Position by more than McQuay OM 920-1...
  • Page 81 One of these lines is the Humidity Ratio versus the dry bulb temperature for saturated air. The other line is the exhaust air process line. The exhaust air process is defined by two points on a psychometric chart (Figure 8). McQuay OM 920-1...
  • Page 82 Intersection Point plus the Maximum Temperature Difference and the enthalpy wheel has been off for longer than the Enthalpy Wheel Minimum Off Time, the wheel will be restarted and will run at its minimum speed. McQuay OM 920-1...
  • Page 83 Whenever a variable speed exhaust fan is on, its capacity will be modulated using a VFD. The speed of the fan will be either (1) modulated to maintain the building static pressure at a desired value or (2) set at a fixed speed provided by a Building Automation System via a network. McQuay OM 920-1...

  • Page 84: Outside Air Damper Control

    1% below the actual effective minimum position normal operation will begin. If the unit enters the Economizer operating state before the damper regulation begins, the regulation will begin from the current economizer position. McQuay OM 920-1...
  • Page 85 Min OA Reset Type = IAQ VDC Example Figure 9: Damper Position vs. Fan Speed Chart Vent Limit = Lo Flow Vent Limit = (Default 20%) (Default 30%) Min Clg Speed = (Default 40%) 100% (Minimum) Airflow – Min OA Type = None McQuay OM 920-1...

  • Page 86: Outside Air Damper Control, Two Position

    • Analog Output (100%OA Units) - The OA damper is driven to its 100% open position when the OA damper analog output is at its maximum value and it is driven closed when the OA damper analog output is at its minimum value McQuay OM 920-1...
  • Page 87 When the Bypass Valve is closed, all water flows through the waterside economizer before it flows through the condenser. When the Bypass Valve is open, all water that flows into the self- contained unit flows directly to the condenser without any water going through the waterside economizer. McQuay OM 920-1...
  • Page 88 • All Cooling is disabled (other than due to Off-Ambient or Off No Flow) • Control Temperature less than or equal to the Zone Cooling Setpoint by more than ½ the Zone Cooling deadband In Mechanical Cooling states, the Bypass Valve is closed when: McQuay OM 920-1...
  • Page 89 This is required when transitioning to the Cooling state from the Fan Only or Economizer state. McQuay OM 920-1...

  • Page 90: Special Procedures For Units With Wrv And More Than Two Circuits

    • Control of the WRV reverts to normal PI control if either Compressor # 1 or Compressor # 2 is enabled and turned on • All compressors are disabled if EWT drops below the MinWRV@ value by more than the OATClgLkDiff. Compressors are re-enabled if EWT rises above the MinWRV@Tmp value McQuay OM 920-1...

  • Page 91: Water Pump Control

    • If neither circuit is disabled, the staging sequence is Std-1 if compressor # 1 has fewer hours than compressor # 3, and the staging sequence is Std-2 if compressor # 1 does not have fewer hours than compressor # 3 • Maximum cooling stages is set to 4. McQuay OM 920-1...
  • Page 92 • the disabled circuit stays off if it is already off and is turned off if it is on. Table 56: Standard Staging Standard Staging Staging Sequence Stage 1 Compressor Stage 2 Compressors Std-1 Std-2 StgdClgCap 100% McQuay OM 920-1...
  • Page 93 • Any compressor on a disabled circuit stays off if it is already off and is turned off if it is on. Table 58: Standard Staging Standard Staging Staging Sequence Stage 1 Compressor Stage 2 Compressors Stage 3 Compressors Std-1 1,2,3 Std-2 1,2,3 StgdClgCap 100% McQuay OM 920-1...
  • Page 94 • The Staging sequence is the Standard sequence that contains the enabled Stage 1 Compressor with the fewest run hours. Compressors in disabled circuits are ignored when only enabled compressor run hours are compared. Maximum cooling stages is set to 4. McQuay OM 920-1...
  • Page 95 • Any compressor on a disabled circuit stays off if it is already off and is turned off if it is on. Table 62: Standard Staging Standard Staging Staging Stage 1 Stage 2 Stage 3 Stage 4 Sequence Compressor Compressors Compressors Compressors Std-1 1,3,4 1,2,3,4 Std-2 2,3,4 1,2,3,4 StgdClgCap 100% McQuay OM 920-1...
  • Page 96 Comps Comps Comps Comps Comps Alt-1 1,3,5 1,2,3,5 1,2,3,4,5 1,2,3,4,5,6 Alt-2 2,4,6 1,2,4,6 1,2,3,4,6 1,2,3,4,5,6 Alt-3 1,3,5 1,3,4,5 1,3,4,5,6 1,2,3,4,5,6 Alt-4 2,4,6 2,3,4,6 2,3,4,5,6 1,2,3,4,5,6 Alt-5 1,3,5 1,3,5,6 1,2,3,5,6 1,2,3,4,5,6 Alt-6 2,4,6 2,4,5,6 1,2,4,5,6 1,2,3,4,5,6 StgdClgCap 100% McQuay OM 920-1...
  • Page 97 It also means that units will remain at a stage for an extra stage times when staging down if a disabled circuit is turned off at that stage. McQuay OM 920-1...
  • Page 98 Std-4 3,4,5 3,4,5,6 2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6,8 1,2,3,4,5,6,7,8 Std-5 4,5,6 3,4,5,6 3,4,5,6,7 3,4,5,6,7,8 1,3,4,5,6,7,8 1,2,3,4,5,6,7,8 Std-6 5,6,7 5,6,7,8 1,5,6,7,8 1,2,5,6,7,8 1,2,3,5,6,7,8 1,2,3,4,5,6,7,8 Std-7 1,7,8 1,2,7,8 1,2,6,7,8 1,2,5,6,7,8 1,2,4,5,6,7,8 1,2,3,4,5,6,7,8 Std-8 6,7,8 5,6,7,8 4,5,6,7,8 3,4,5,6,7,8 2,3,4,5,6,7,8 1,2,3,4,5,6,7,8 ClgCap 100% McQuay OM 920-1...
  • Page 99 Std-4 3,4,5 3,4,5,6 2,3,4,5,6 1,2,3,4,5,6 1,2,3,4,5,6,8 1,2,3,4,5,6,7,8 Std-5 4,5,6 3,4,5,6 3,4,5,6,7 3,4,5,6,7,8 1,3,4,5,6,7,8 1,2,3,4,5,6,7,8 Std-6 5,6,7 5,6,7,8 1,5,6,7,8 1,2,5,6,7,8 1,2,3,5,6,7,8 1,2,3,4,5,6,7,8 Std-7 1,7,8 1,2,7,8 1,2,6,7,8 1,2,5,6,7,8 1,2,4,5,6,7,8 1,2,3,4,5,6,7,8 Std-8 6,7,8 5,6,7,8 4,5,6,7,8 3,4,5,6,7,8 2,3,4,5,6,7,8 1,2,3,4,5,6,7,8 ClgCap 100% McQuay OM 920-1...
  • Page 100 Evaporative Condensing. In this case, the sump pump must be turned on before any compressor is turned on. If there is a sump pump fail condition, cooling will stay in stage 0. McQuay OM 920-1...
  • Page 101 • The time since the last stage change exceeds the Cooling stage timer AND • Dehumidification is active AND • Leaving Coil Temperature is less than the Minimum leaving coil Setpoint AND • Current Stage is greater than 0 McQuay OM 920-1...
  • Page 102 Effective Discharge Cooling Set Point by more than half the Discharge Cooling Dead Band (as shown just after Point 6), a stage down does not occur because DTB remains less than DTA. The discharge air temperature starts rising again because the load is increasing. McQuay OM 920-1...
  • Page 103 The number of Compressor Stages increases when: • The time since the last stage change exceeds the Cooling stage timer AND • Projected Control Temperature is greater than the Zone cooling Setpoint by more than half the deadband AND McQuay OM 920-1...
  • Page 104 Cooling State. The Effective Project Ahead Time is set equal to the Heating Project Ahead Time when a unit with staged heating is in the Heating State. It is set equal to zero under all other conditions causing the Projected Control temperature to equal the Control Temperature McQuay OM 920-1...

  • Page 105: Cooling: Modulating

    When Space, Return, OAT, or Airflow is selected, it only makes sense for the DAT Cooling setpoint to decrease as the selected temperature increases as shown in the graph below. Figure 12: Cooling Setpoint Max Clg Spt Min Clg Spt Max Clg Spt @ Min Clg Spt @ McQuay OM 920-1...
  • Page 106 Note – During the phase in/out period of R22 to R410A there will be a time period in which a third condenser fan output will be required on R22 units. This output will be designated Cond Fan Output C (EMA-DO3). McQuay OM 920-1...
  • Page 107 Setpoint Differential Setpoint Differential Note: PC13/PC23: Cut in= 450 PSIG (125F sat.). Cut out= 275 PSIG (90F sat.). Table 72: R-22 Condenser Fan Setpoints CondFanOutputA CondFanOutputB CondFanOutputC (MCB-D07) (MCB-D08) (MCB-D06) Unit Size Setpoint Differntial Setpoint Differential Setpoint Differential McQuay OM 920-1...
  • Page 108 Condenser fans #2 and # 3 on each compressor circuit is turned on and off using the two outputs on the Main Board that are used for standard condenser fans. Relays are driven by each of these outputs so that fans associated with a circuit that is not operating will not be turned on. McQuay OM 920-1...
  • Page 109 When condenser fan must be turned off for normal operation, the output that has been on for the longest period of time is turned off. McQuay OM 920-1...

  • Page 110: Heating Control

    • CtrlTemp is greater than the Zone Htg Spt (plus ½ the deadband) AND • The current heating stage is greater than zero • The time since the last stage change exceeds the Stage Time AND • DAT is greater than the DATSpt AND McQuay OM 920-1...

  • Page 111: Modulating

    These are the “Open Valve” and “Modulating Valve” methods and are described in the following sections. The parameter is adjustable via the following path: Extended Menus/Heating Setup/F&BP Method. McQuay OM 920-1...
  • Page 112 # 6 on the FSG. The FSG then energizes its terminal #4, which powers the burner combustion air blower motor (BM) and starts the 90 second prepurge cycle. The controller will reposition the burner air valve to its maximum open position via analog output EXPB- McQuay OM 920-1...
  • Page 113 10 seconds, terminals #4, 8, 9, and 10 will be de-energized, thus de-energizing the burner. The FSG will then lockout and require manual resetting. If the FSG lockout occurs, FSG terminal #3 will energize the R24 alarm input status relay which will 'make' a digital McQuay OM 920-1...
  • Page 114 This calculated position is based on the “Application Discharge Air Temperature Setpoint”, the Outdoor Air Temperature, and the Maximum Temperature Rise of the Gas Heat Exchanger using the following formula: Gas Heat Actuator Position = 100% x (Setpoint - Outdoor Air Temp) / Temp Rise McQuay OM 920-1...
  • Page 115 Discharge Heating Spt equals the Min Htg Spt when the selected value equals the Min Htg Spt @ value. When Space, Return, or OAT is selected, it only makes sense for the DAT Heating setpoint to decrease as the selected temperature increases as shown in the graph below. McQuay OM 920-1...
  • Page 116 Discharge Cooling Set Point varies linearly between the Minimum Discharge Cooling Set Point and Maximum Discharge Cooling Set Point. This is shown as Point B in Figure 13. Figure 13: Discharge Temperature Reset Based on Temperature McQuay OM 920-1...

  • Page 117: Indoor Air Fan - On/Off Control

    This value reverts to zero when the unit is off and remains at that value after startup until a non zero value is written via the network or the keypad/display. McQuay OM 920-1...
  • Page 118 • The Exhaust Fan is controlled by a VFD • The Remote Exhaust Fan capacity is commanded to less than or equal to its minimum value (Default = 5%) for longer than the Minimum Exhaust Stop Time (Default = 120 seconds) McQuay OM 920-1...
  • Page 119 When this method is chosen, the user may also choose to have a Low Limit prevent the minimum from being set too high. This low limit can use the discharge or the entering fan temperature sensor. McQuay OM 920-1...
  • Page 120 The exhaust fan does not start until a value greater than the minimum value is written by the network or keypad/display. McQuay OM 920-1...
  • Page 122 McQuay Training and Development Now that you have made an investment in modern, efficient McQuay equipment, its care should be a high priority. For training information on all McQuay HVAC products, please visit us at www.mcquay.com and click on training, or call 540-248-9646 and ask for the Training Department.

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