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– Compressors
– Condenser fans
– Unloader solenoids
– Heat stages
• All equipment control analog outputs are set to their minimum/off command values.
• All communicating devices, such as supply fans, are commanded to their off state.
• All control algorithms are initialized to their normal startup values and held until the stop request is
released.
The Unit Stop request can be initiated from the following sources:
• Unit Stop Command
• Equipment Shutdown Input
• Emergency Override BAS
• Phase Monitor
If a Unit Stop is initiated, the source of the Unit Stop can be determined by the Unit Stop Source Point
and other status/diagnostic points.
Capacity Limit Control
There are three sources for capacity limitation provided by the Symbio™ 700:
• BAS Lockout Function
• BAS Capacity Enable function
• Demand Limit Function
Depending on how the controller application is configured, different portions of the capacity limit control
can be active at any time. Because of this, a priority scheme is built into the capacity limitation function.
If cooling is allowed from “Cooling Lockout BAS – Active” and if Demand Management is configured for
Demand Limit, “Cooling Demand Limit Capacity Enable Setpoint – Active” or “Heating Demand Limit
Capacity Enable Setpoint – Active” will be used to limit the unit capacity if it is active and “Cooling
Capacity Enable – Active” is not limiting capacity. If “Cooling Capacity Enable – Active” is set to a value
less than 100, “Cooling Capacity Enable – Active” has priority.
For capacity limiting values for user selected values, refer to the Appendix section of this document.
Remote Capacity Control
The Symbio™ 700 controls support the Remote Capacity Control function for all system types except
VVDA. This function allows a user to directly control the unit capacity rather than allowing the internal
algorithm to provide control.
The following features/functions can be requested directly via points, rather than relying on internal
temperature or thermostat control sequences:
• Supply Fan Speed
• Cooling Capacity
• Heating Capacity
For Thermostat Controlled equipment, the Thermostat Inputs must be "OPEN" i.e. requesting "OFF"
mode before the Cooling or Heating Capacity requests will be honored.
For Space Temperature controlled equipment, the Heat Cool Mode Request must be set to "Fan Only"
before the Cooling or Heating Capacity requests will be honored.
For each entity, there is an "Enable" point to enable or disable the remote capacity control, and an
analog value point to allow the user to request an analog capacity value. The analog value is translated
to the appropriate value per function.
Supply Fan Speed Command overrides will be honored in all non-Heat or Off modes. When Supply Fan
Speed Command is enabled, and the Supply Fan Speed Command value is 0%, the system will
interpret as an "OFF" mode request, and all active capacity will be set to "Off"; fan, heating, and cooling.
Building Automation System Support Sequences
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