Trane RAUL 190, Manual

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11 RAU-SVX01G-GB
Installation
Functional description
The hot gas bypass solenoid valve will be controlled by a normally open (NO) relay output. Energizing the solenoid
will open the valve.
Freeze avoidance or evaporator limit will also operate while in the hot gas-bypass mode. Shutdown of the unit when
in hot gas-bypass due to evaporator limit will not result in any diagnostics and the unit will restart normally when
there is a need to run.
Total time spent in hot gas bypass mode will be recorded and available to the user.
Design details
The following rules will be applied to hot gas bypass operation, if hot gas bypass is installed and enabled.
1. Hot gas bypass will be opened when the circuit is running with compressors at the minimum (fi rst) capacity step
and the control algorithm requires a further reduction in capacity.
2. Hot gas bypass will be closed at circuit startup.
3. Hot gas bypass will be closed when it is already open, but additional capacity is required.
4. Hot gas bypass will be closed and the circuit shut down if the unit has been running with hot gas-bypass for
more than the hot gas-bypass time limit.
5. Hot gas bypass will be closed and the compressor shut down if the saturated suction temperature for Circuit 1
gets below the Low Refrigerant Temperature 0.5°C.
Capacity control modes
RAUL units support air temperature control and external capacity control (optional), which are described below.
At least one of these options must be confi gured.
Air temperature control (standard)
Units with an evaporator leaving air temperature sensor is capable of air temperature control. Air temperature
control is used on RAUL units if the external capacity control feature is not selected.
Air temperature control will require an active air temperature setpoint, based on a front panel air temperature
setpoint, an external air temperature setpoint, a BAS air temperature setpoint, and a local schedule air temperature
setpoint. These settings are displayed on DynaView and TechView similarly to the existing chilled water setpoint
values.
The capacity control method is identical to that used for chilled water control, with setting changes being used to
adjust the control appropriately.
External capacity control (option)
Optional replace air temperature control
External capacity control be a confi gurable option for RAUL units. The confi guration options are as follows:
• Not Installed
• 2 Low Voltage Binary Inputs (2 capacity steps)
• 3 Low Voltage Binary Inputs (3 capacity steps)
• 4 Low Voltage Binary Inputs (4 capacity steps)
When in external capacity control mode, the unit is in AUTO command mode, and there is no need to run, “waiting
for need to run” submode is displayed.
Communication failure with any of the external capacity control hardware inputs will cause a shutdown of the unit if
the external capacity control feature is confi gured and enabled.
External capacity control overrides any other capacity control mode except manual control mode if enabled.