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Sequence of Operation
Stopped is a Unit mode when control is prevented from
running. For example, if External Auto/Stop binary input is
active, External Auto Stop will be listed as a sub-mode.
Run Inhibit
The unit is currently being inhibited from starting and
running. For example, if a Power Up Delay timer is
preventing the unit startup, Power Up Delay Inhibit (Min:
Sec) will be listed with the remaining minutes and seconds
to expire.
Auto
The unit supply fan is typically running to provide
ventilation. Idle is listed as a sub-mode on startup when the
control is determining an initial heating or cooling demand.
Additional sub-modes are listed when gas heat diagnostics
are preventing heat operation.
Running
Running is a Unit mode then normal heating, cooling and
ventilation control functions are active. The supply fan is
running. Up to four Running sub-modes will be listed on the
user interface, Operating Modes screen.
Circuit
Circuit modes provide refrigerant circuit level operating
state and sub-mode information. When the unit has two
circuits, the user interface will provide both Circuit 1 and
Circuit 2 mode and sub-mode information.
Stopped
The circuit is not running, and cannot run without removing
a condition. For example, Diagnostic Shutdown – Manual
Reset sub-mode is displayed when a diagnostic has
caused a circuit level shutdown and a manual reset is
required.
Run Inhibit
The circuit is currently being inhibited from starting (and
running), but may be allowed to start if the inhibiting or
diagnostic condition is cleared. For example: Low Ambient
Temp is displayed when outdoor air temperature is below
the Low Ambient Lockout Setpoint; the circuit is being
inhibited from starting.
Auto
The circuit is not running but expected to start given the
proper conditions are satisfied.
Waiting to Start
The circuit is going through the necessary steps to allow
the circuit to start; for example, EXV is being commanded
to a pre-position prior to starting a compressor.
Running
A compressor on a given circuit is currently running.
Running — Limit
The circuit is currently running; however, the operation of
the unit/compressors is actively limited by the controls.
Active compressor protection sub-modes will be listed. See
Compressor Protections section for more information.
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Shutting Down
The circuit is preparing to de-energize the compressor. For
example, Diagnostic Shutdown – Manual Reset is
displayed when the circuit is shutting down on a latching
diagnostic.
Unit Sub-Modes
Morning Warm Up
Morning Warm Up is an optional feature when heat is
configured and can be Enabled or Disabled. Morning Warm
Up is a mode often used during building unoccupied
periods and optimal start applications to rapidly increase
the space temperature, as efficiently as possible, before
building occupancy. The outdoor air damper minimum
position setpoint will be overridden to 0%, ventilation air is
not provided during Morning Warm Up.
For Morning Warmup to initiate on a transition from
Unoccupied to Occupied, Space temperature control units
must be in Heat, Max Heat, or Auto. Discharge air control
units can also initiate Morning Warm Up on an Off to
Occupied transition.
For all equipment types (Constant Volume, Multi Zone-VAV,
and Single Zone VAV): On a transition from Unoccupied to
Occupied or Occupied-Standby, and with a valid space
temperature 1.5° F below the Morning Warmup Setpoint,
morning warm up operation initiates. Heat Cool Mode
Status reports maximum heat if the heat type requires full
airflow and VAV Box Relay binary output will energize (see
Maximum Heat for details). Otherwise, heat types that
allow modulating airflow will report heat.
The Symbio 800 operates in a discharge air control mode
delivering heating capacity per Discharge Air Heating
Setpoint Active; this provides flexibility when 100% heat
capacity in not desired. The supply fan operates at max
speed on Constant Volume Units. Variable air volume
discharge air control units will operate the supply fan per
Duct Static Pressure Setpoint, if the installed heat type
allows. (See Heat Types section for more information).
When 60 minutes expires or when space temperature
equals or exceeds the Morning Warmup Setpoint, Morning
Warm Up mode will terminate.
Morning Warm Up mode can also be commanded via Heat
Cool Mode Request from a building automation system or
external control. In this case, the unit remains in Morning
Warm Up mode indefinitely until the commanded mode is
removed or changed. When the space temperature
exceeds the Morning Warmup Setpoint, heating capacity is
disabled but the supply fan operation continues to circulate
air until the Morning Warm Up command is removed. Heat
capacity will re-enable if space temperature falls 1.5°F
below Morning Warmup Setpoint.
Pre Cool
Pre Cool is a feature of the unit and can be Enabled, or
Disabled. Pre Cool is a mode often used during building
unoccupied periods and optimal start applications to rapidly
RT-SVX063G-EN
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