RT-SVX063E-EN
65
Sequence of Operation
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Stop/Off/Auto
There are a number of reasons the Symbio 800
controller will have the IntelliPak unit stopped or off.
The user interface home screen displays unit mode of
Stopped or Auto. Stopped is indicated when an
override is preventing operation such as: Local Stop,
Emergency Stop or External Stop input is active. Auto
is indicated when in automatic control but is currently
off in modes such as: Unoccupied, Ventilation
Override, Emergency Override or the like.
When Heat Cool Mode Status is Off, unit operation will
be prevented; whereas, all other modes allow
operation.
Power-Up Start Delay
Anytime power is apply to the unit or the controller is
reset, and the unit is able to run, a user adjustable
Power-Up Start Delay setting is enforced to allow
staggered starts of multiple units. The user interface
home screen displays Run Inhibit when active. Power
Up Delay Inhibit, with remaining minutes and seconds,
will be displayed on user interface operating modes
screen. Power-Up Start Delay is also applies to Rapid
Restart, or when the controller exits Ventilation
Override or Emergency Override modes.
Normal Unit Starting
When Local Stop, Stop modes, overrides, and
diagnostic shutdowns are removed, the controller will
start unit operation. The supply fan starts and increases
to the minimum Hz setting and must prove On. Unit
mode Running is displayed on the user interface. The
supply fan will run for one minute, with the outdoor air
damper closed, before transitioning into an active heat
or cool mode.
Rapid Restart Operation
The purpose of rapid restart is to insure the space
temperature recovers from high heating loads once the
unit has recovered from a power outage. This is
accomplished by utilizing aggressive economizing and/
or compressor staging in a user adjustable amount of
time. After a Rapid Restart event, the unit can
subsequently manage the load using normal capacity
control. A typical application is a data center.
The unit configuration must have Rapid Restart
configured as “Installed” and the Rapid Restart Enable
setting must be set to “True” to allow this function to
operate. Mechanical cooling (DX) is available for Rapid
Restart if the Outdoor Air Temperature is above the
Low Ambient Lockout setpoint.
After power-up start delay is satisfied, the unit will
override all other forms of time delays (i.e. ICS, VAV
Box Stroke Time, Outdoor Air Damper Stroke Time)
and allow the Supply Fan to start. Once the Supply Fan
has proven, the unit will determine the proper staging
sequence by processing outdoor air temperature and
return air temperature. The unit will generate a Rapid
Restart mode annunciation on the user interface,
operating modes screen.
VOM and Emergency Override have higher priority
than Rapid Restart. If either occur, Rapid Restart will be
terminated and the VOM or Emergency Override will
be performed. Demand limit also has priority over
Rapid Restart.
The unit will terminate Rapid Restart and will de-
energize the VAV Box Relay (if installed), and release to
normal unit control when the Cooling Capacity Status
meets or exceeds the Rapid Restart Capacity Target or
when the Rapid Restart Termination Time expires.
Occupancy
There are many sources and types of occupancy. These
have an effect on the operation of the IntelliPak unit. All
sources are arbitrated (prioritized) into a final
occupancy status.
Sources of Occupancy
• Occupancy Request is a communicated value from
a Building Automation System (BAS) schedule.
• Occupancy Input is a local input from the space
served by the equipment. These are typically
optional local time clocks or occupancy sensors.
This is a physical input to the Symbio controller and
is field installed.
• Bypass Timer starts because of a user requested
occupancy override (also known as Occupied
Bypass). The occupant requests temporary
occupied comfort heating or cooling during
unoccupied scheduled time periods. An example of
this would be the Timed Override (TOV) button on
the zone sensor. See “Timed Override,” p. 66 for
more information.
Occupancy Status Definitions
OOccccuuppiieedd OOppeerraattiioon: The IntelliPak unit is running in a
Normal mode providing temperature and ventilation
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