Ice Building Option; External Chilled Water Setpoint (Ecws) Option; External Demand Limit Setpoint (Edls) Option - Trane Tracer TD7 User Manual

Installation Electrical
These customer-supplied contact closures must
be compatible with 24 VDC, 12 mA resistive load.
Silver or gold plated contacts are recommended.

Ice Building Option

UC800 provides auxiliary control for a customer
specifi ed/installed correct with contact closure 5K20 for
ice building if so confi gured and enabled. This output
is known as the Ice Building Status Relay. The normally
open contact will be closed when ice building is in
progress and open when ice building has been normally
terminated either through Ice Termination setpoint being
reached or removal of the Ice Building command. This
output is for use with the ice storage system equipment
or controls (provided by others) to signal the system
changes required as the chiller mode changes from
"ice building" to "ice complete" . When contact 5K12 is
provided, the chiller will run normally when the contact
is open.
UC800 will accept either an isolated contact closure
(External Ice Building command) or a Remote
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 31°F (-6.7 to -0.5°C) in at least 1°F (1°C)
increments.
Note: 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.
NOTICE:
Equipment Damage!
Freeze inhibitor must be adequate for the leaving water
temperature. Failure to do so will result in damage to
system components.
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 (open 5K12 contacts) and
then switched back into ice building mode (close 5K12
contacts.)
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.
10
Connect leads from 5K12 to the proper terminals of
1A15. Refer to the fi eld 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 Water Setpoint
(ECWS) Option
The UC800 provides inputs that accept either 4-20 mA or
2-10 VDC signals to set the external chilled water setpoint
(ECWS). This is not a reset function. The input defi nes the
setpoint. This input is primarily used with generic BAS
(building automation systems). The chilled water setpoint
set via the Tracer TD7 or through digital communication
with Tracer (Comm4). The arbitration of the various
chilled water setpoint sources is described in the fl ow
charts at the end of the section.
The chilled water setpoint may be changed from a
remote location by sending either a 2-10 VDC or 4-20 mA
signal to the 1A14, terminals 5 and 6 LLID. 2-10 VDC and
4-20 mA each correspond to a 10 to 65°F (-12 to 18°C)
external chilled water setpoint.
The following equations apply:
Voltage Signal
As generated from external source
As processed by UC800
Current Signal
As generated from external source
As processed by UC800
If the ECWS 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 the External
Chilled Water Setpoint option as well as a means to
enable and disable ECWS.
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 TD7
or through digital communication with Tracer (Comm4).
The arbitration of the various sources of demand limit is
described in the fl ow 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 1A14 LLID terminals 2 and 3. Refer to the following
paragraph on Analog Input Signal Wiring Details.
VDC=0.1455*(ECWS) + 0.5454
ECWS=6.875*(VDC) - 3.75
mA=0.2909(ECWS) + 1.0909
ECWS=3.4375(mA) - 3.75
RLC-SVU006A-E4