Leaving Water Temperature Cutout; Low Refrigerant Temperature Cutout - Trane RTAA-70 Installation & Maintenance Manual

RTAA-SVX01A-EN
Controls Interface

Leaving Water Temperature Cutout

This temperature cutout provides protection against freezing caused by low
leaving water temperature. The setpoint is both factory set and adjustable
from the Service Settings Menu. Temperatures below the setpoint will cause
the UCM to accelerate reduction of chiller capacity, even to the point of
compressor shutdown. A non-latching diagnostic will be generated if the LWT
is below the cutout for more than 30 degree F seconds. See Table 10 for
proper settings.
There must be a minimum of 5 F between the cutout temperature and both
the front panel and active chilled water setpoints. The Clear Language Display
will not permit setting of either the front panel or active chilled water temper-
atures less than 5 F above this cutout temperature. The second line will state
"Limited by Cutout Setpoint, (+) to change" .
If the leaving water temperature cutout is set upward, the Clear Language
Display will maintain the 5 F minimum and will automatically raise the
settings on the front panel and active chilled water setpoints, if necessary.
If the front panel or Active Chilled Water Setpoints were adjusted, the display
will show the following when the "Enter" key is pressed:
"FRONT PANEL CHILLED WATER SETPOINT
HAS BEEN INCREMENTED DUE TO CUTOUT
If the leaving water temperature drops below the cutout setpoint while the
compressors are de-energized, it will produce an IFW diagnostic. If the
leaving water temperature drops below the cutout setpoint while the
compressors are energized for 30 F seconds, the unit will shut down on an
MAR diagnostic.

Low Refrigerant Temperature Cutout

Both circuits are protected from a saturated evaporator refrigerant temper-
ature that goes below this setting. The cutout setpoint must be a minimum of
15 F lower than the front panel or active chilled water setpoints. See Table 17
for proper settings.
There must be a minimum of 15 F between the cutout temperature and both
the front panel and active chilled water setpoints. The Clear Language Display
will not permit setting of either the front panel or active chilled water temper-
atures less than 15 F above this cutout temperature and the display will flash
the last valid temperature.
If the leaving water temperature cutout is set upward, the Clear Language
Display will maintain the 15 F minimum and will automatically raise the
settings on the front panel and active chilled water setpoints, if necessary.
If the front panel or Active Chilled Water Setpoints were adjusted, the display
will show the following when the "Enter" key is pressed:
"FRONT PANEL CHILLED WATER SETPOINT
HAS BEEN INCREMENTED DUE TO CUTOUT
If the saturated evaporator refrigerant temperature for a circuit drops below
this setpoint for longer than 30 degree F seconds, the circuit will be
shutdown and a CMR diagnostic will be displayed.
NOTE: Ice Termination will allow cutouts to be set anywhere, although
when running, software follows 5 F and 15 F rules.
SETPOINT CHANGE"
SETPOINT CHANGE"
97