Instruction manual
Table Of Contents
- Introduction
- Using the Keypad/Display
- Keypad/Display Menu Structure
- System Summary Menu
- Standard Menus
- System Menu
- Occupancy Menu
- Temperature Menu
- Flow Summary Menu
- Supply Fan Speed Menu
- Return/Exhaust Fan Speed Menu
- Cooling Menu
- Head Pressure Menu
- Evap Condensing Menu
- Economizer Menu
- Min OA Damper Menu
- Heating Menu
- Energy Recovery
- Dehumidification Menu
- Daily Schedule Menu
- One Event Schedule Menu
- Holiday Schedule Menu
- Optimal Start Menu
- Operating Hours Menu
- Extended Menus
- Unit Setup Menu
- Timer Settings Menu
- Time/Date Menu
- Supply Fan Setup Menu
- Return/Exhaust Fan Setup Menu
- Zone Temperature Setup Menu
- Compressor Setup Menu
- Head Pressure Setup Menu
- Chilled Water Setup Menu
- Economizer Setup Menu
- Design Flow Setup Menu
- Heating Setup Menu
- Dehumidification Setup Menu
- Alarm Out Configuration Setup Menu
- Alarm Limits Setup Menu
- Manual Control Menu
- LON/BACnetIP/BACnetMSTP Setup Menu
- Active Alarm Menu
- Alarm Log Menu
- Advanced Menus
- Unit Configuration Setup Menu
- Save/Restore Menu
- Alarm Delays Setup Menu
- Analog Input Status Menu
- Universal I/O Status Menu
- Digital Input Status Menu
- Digital Output Status Menu
- Adv Setup Settings Menu
- Adv Status Parameters Menu
- Alarms
- Operator’s Guide
- Determining Unit State
- Off Operating State
- Start Up Operating State
- Recirculating Operating State
- Heating
- Economizer
- Mechanical Cooling
- Determining Unit Status
- Determining Control Mode
- Determining Cooling Status
- Determining Heat Status
- Determining Economizer Status
- Determining Cooling Capacity
- Determining Heating Capacity
- Determining Supply Air Fan Capacity
- Determining RF/EF Capacity
- Determining Outside Air Damper Position
- Determining Emergency Mode
- Determining Application Mode
- Determining Occupancy Status
- Determining Occupancy Mode
- Determining Occupancy Source
- Unoccupied Operation
- Scheduling
- Temperature Control Configurations
- Heat/Cool Changeover
- Dehumidification
- Energy Recovery
- Outside Air Damper Control
- Outside Air Damper Control, Two Position
- Special Procedures for Units with WRV and More Than Two Circuits.
- Water Pump Control
- Cooling: Multistage
- Cooling: Modulating
- Heating Control
- Modulating
- Min DAT
- Indoor Air Fan - On/Off Control
66 McQuay OM 920
Operator’s Guide
Determining Unit Status
Unit Status is a status only item which indicates whether or not the unit is enabled and if not
why. The current Unit Status can be viewed via the following path: Standard
Menu/System/Unit Status.
Enabled
Unit operation has not been disabled for any of the following reasons.
OFF Manual
The unit operating state is Off Manual when the control mode is set to OFF via the keypad.
The control mode can only be changed via the System menu on the keypad/display.
OffManCtrl
The unit operating state is Off manual control when the controller is set to manual control via
the Manual Control menu.
OFF Network
The unit operating state is Off Network when the control mode is set to Auto via the 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.
Off Fan Retry
The unit operating state is Off Fan Retry when The Fan Retry conditions below indicate that
the unit should be shutdown and restarted after airflow is lost.
• The supply fan is controlled by a VFD
• The airflow switch (PC7) is open AND the duct static pressure is less than ½ the duct static
pressure setpoint
• There are no active faults that would shut down the unit
Determining Control Mode
The unit cooling and heating can be set up for automatic heat/cool, cool only, heat only, fan
only, or network cool/heat operation by setting the Control Mode via the following path:
Standard Menu/System/Ctrl Mode. The unit can also be manually disabled via the Control
Mode. The following are descriptions of the six available Control Mode selections.
Off
When the Control Mode is set to “Off,” the Unit Status is “Off Man” and the unit is
completely disabled.
Heat Only
When the Control Mode is set to “Heat Only,” heating operation is allowed to operate to
maintain the heating set points. Cooling operation is disabled (Cooing Status is “Off Man”).
Cool Only
When the Control Mode is set to “Cool Only,” cooling operation is allowed to operate to
maintain the cooling set points. 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”).