AC-SVX002C-EN
41
Communicated input (Tracer) to initiate and command
the Ice Building mode.
UC800 also provides a “Front Panel Ice Termination
Setpoint”, settable through Tracer
®
TU, and adjustable
from 20 to 32°F (-6.7 to 0°C) in at least 1°F (1°C)
increments.
N
No
otte
e:: When in the ice building mode, and the
evaporator entering water temperature drops
below the ice termination setpoint, the chiller
terminates the ice building mode and changes to
the ice building complete mode.
N
NO
OT
TIIC
CE
E
E
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Tracer
®
TU must also be used to enable or disable Ice
Machine Control. This setting does not prevent the
Tracer from commanding Ice Building mode.
Upon contact closure, the UC800 will initiate an ice
building mode, in which the unit runs fully loaded at all
times. Ice building shall be terminated either by
opening the contact or based on the entering
evaporator water temperature. UC800 will not permit
the ice building mode to be reentered until the unit has
been switched out of ice building mode and then
switched back into ice building mode.
In ice building, all limits (freeze avoidance, evaporator,
condenser, current) will be ignored. All safeties will be
enforced.
If, while in ice building mode, the unit gets down to the
freeze stat setting (water or refrigerant), the unit will
shut down on a manually resettable diagnostic, just as
in normal operation.
Connect leads to the proper terminals. Refer to the field
diagrams which are shipped with the unit.
Silver or gold-plated contacts are recommended. These
customer furnished contacts must be compatible with
24 VDC, 12 mA resistive load.
External Chilled/Hot Water Setpoint
(ECHWS) Option
The UC800 provides inputs that accept either 4-20 mA
or 2-10 VDC signals to set the external chilled/hot water
setpoint (ECHWS). This is not a reset function. The
input defines the setpoint. This input is primarily used
with generic building automation systems (BAS).
When the unit is in cooling mode, the external water
setpoint (EWS) corresponds to the chilled water
setpoint.
When the unit is in heating mode, the external water
setpoint (EWS) corresponds to the hot water setpoint.
The external water setpoint shall have a configurable
minimum and maximum set for cooling, and another
one for heating.
The setpoints may be changed from a remote location
by sending either a 2-10 VDC or 4-20 mA signal that
corresponds to an EWS range with a configurable
minimum and maximum value.
Table 20.
Setpoint/signal relationships
Input Signal
External Water Setpoint
< 1 VDC
Invalid
1 VDC to 2 VDC
min
2 VDC to 10 VDC
min + (max – min) * (Signal – 2) / 8
10 VDC to 11 VDC
max
> 11 VDC
Invalid
< 2 mA
Invalid
2 mA to 4 mA
min
4 mA to 20 mA
min + (max – min) * (Signal – 4) /
16
20 mA to 22 mA
max
> 22 mA
Invalid
If the ECHWS input develops an open or short, the LLID
will report either a very high or very low value back to
the main processor. This will generate an informational
diagnostic and the unit will default to using the front
Panel (TD7) Chilled Water Setpoint.
Tracer
®
TU Service Tool is used to set the input signal
type from the factory default of 2-10 VDC to that of 4-20
mA. Tracer
®
TU is also used to install or remove,
enable or disable, the External Chilled Water Setpoint.
External Demand Limit Setpoint (EDLS)
Option
Similar to the above, the UC800 also provides for an
optional External Demand Limit Setpoint that will
accept either a 2–10 VDC (default) or a 4–20 mA signal.
The Demand Limit Setting can also be set via the
Tracer AdaptiView™ TD7 or through digital
communication with Tracer (Comm4). The arbitration
of the various sources of demand limit is described in
the flow charts at the end of this section. The External
Demand Limit Setpoint may be changed from a remote
location by hooking up the analog input signal to the
1A19 LLID terminals 5 and 6. Refer to the following
paragraph on Analog Input Signal Wiring Details. The
following equations apply for EDLS:
If the EDLS input develops an open or short, the LLID
will report either a very high or very low value back to
the man processor. This will generate an informational
diagnostic and the unit will default to using the Front
Panel (Tracer AdaptiView
™
TD7) Demand Limit
Setpoint.
