Principles of Operation of
the Module UCM-CLD
RLC-SVU02F-E4
10
Chilled-Water Reset (CWR)
As an option, the UCM will reset the
chilled-water temperature setpoint,
based on either the return water
temperature or the outdoor air
temperature. The CSR module is
necessary to perform CWR.
The following are selectable:
One of four reset types, from top to
bottom in order of reset:
no CWR
RETURN WATER TEMPERATURE
RESET
ZONE TEMPERATURE RESET
OUTDOOR AIR TEMPERATURE
RESET
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 Setting
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 16°C-seconds.
There must be a minimum of 2.7°C
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 temperatures
less than 2.7°C above the 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
2.7°C 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 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 16°C-seconds, the unit
will shut down on an MAR
diagnostic.