Trane R Series Installation Operation & Maintenance page 118

Controls Interface
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
SETPOINT CHANGE"
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.
Low Ambient Temperature Start
The Low Refrigerant Temperature Cutout (LRTC) and Low Pressure Cutout
(LPC) on a circuit is ignored, briefly, each time the circuit is started. The
"ignore time" is a function of the Saturated Condenser Refrigerant Temper-
ature at the time the compressor starts, as shown in Figure 40.
Low Refrigerant Temperature Cutout and Low Pressure Cutout Retry
If the LRTC or LPC trips despite the low ambient temperature start logic, the
circuit will be permitted to shutdown and retry one time.
If the LRTC or LPC trips within the first 20 minutes after initial start but after
the low ambient ignore time (grace period), the compressor stops immedi-
ately and the Restart Inhibit timer is set to one minute. After time expires, the
compressor will reset if there is a call for cooling.
If the LRTC or LPC trips again during the grace period, a CMR diagnostic will
occur. If there is an LRTC or LPC trip anytime after the grace period, a CMR
diagnostic will occur.
Balanced Compressor Starts and Hours
This feature is enabled/disabled in Balanced Starts and Hours (Service
Settings Menu). When enabled, the UCM will start the compressor with the
fewest starts and stop the compressor with the greatest hours, as deter-
mined by the "Compressor Starts" accumulator and the "Compressor
Hours" accumulator. This will tend to balance out hours and starts equally
over both compressors.
Figure 40 Low Refrigerant Temp and Low Pressure Cutout Ignore Time
118 RLC-SVX07A-EN