Installation and Maintenance Manual

Installation Electrical
RTAE-SVX001B-EN 39
TWL is leaving evap. water temperature
MAXIMUM RESET is a user adjustable limit providing the
maximum amount of reset. For all types of reset, CWS' -
CWS < or = Maximum Reset.
In addition to Return and Outdoor Reset, the MP provides
a menu item for the operator to select a Constant Return
Reset. Constant Return Reset will reset the leaving water
temperature set point so as to provide a constant entering
water temperature.The Constant Return Reset equation is
the same as the Return Reset equation except on selection
of Constant Return Reset, the MP will automatically set
Ratio, Start Reset, and Maximum Reset to the following.
RATIO = 100%
START RESET = Design DeltaTemp.
MAXIMUM RESET = Design DeltaTemp.
The equation for Constant Return is then as follows:
CWS' = CWS + 100% (Design Delta Temp. - (TWE -TWL))
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
When any type of CWR is enabled, the MP will step the
Active CWS toward the desired CWS' (based on the above
equations and setup parameters) at a rate of 1 degree F
every 5 minutes until the Active CWS equals the desired
CWS'.This applies when the chiller is running.
When the chiller is not running, CWS is reset immediately
(within one minute) for Return Reset and at a rate of 1
degree F every 5 minutes for Outdoor Reset.The chiller
will start at the Differential to Start value above a fully reset
CWS or CWS' for both Return and Outdoor Reset.
Transformer Power Rating
See table below for power rating of optional transformer
(unit model number digit 28 = 1).
Communications Interface
LonTalk Interface (LCI-C)
UC800 provides an optional LonTalk™ Communication
Interface (LCI-C) between the chiller and a Building
Automation System (BAS). An LCI-C LLID shall be used to
provide "gateway" functionality between a LonTalk
compatible device and the Chiller.The inputs/outputs
include both mandatory and optional network variables as
established by the LonMark Functional Chiller Profile 8040.
Note: For more information see ACC-SVN100*-EN.
BACnet Interface (BCI-C)
Optional BACnet™ Communication Interface for Chillers
(BCI-C) is comprised of aTracer UC800 controller with
interface software. It is a non-programmable
communications module that allows units to
communicate on a BACnet communications network.
Note: For more information, see BAS-SVP01*-EN.
Modbus Remote Terminal Unit Interface
Modicon Communication Bus (Modbus™) enables the
chiller controller to communicate as a slave device on a
Modbus network. Chiller setpoints, operating modes,
alarms and status can be monitored and controlled by a
Modbus master device.
Note: For more information, see BAS-SVP01*-EN.
Range Increment
Reset
Type
Reset
Ratio
Start
Reset
Max
Reset
IP
Units
SI
Units
Factory
Default
Return
10 to
120%
4 to 30 F 0 to 20 F 1% 1% 50%
(2.2 to
16.7 C)
(0.0 to
11.1 C)
Outdoor
80 to -
80%
50 to 130
F
0 to 20 F 1% 1% 10%
(10 to
54.4 C)
(0.0 to
11.1 C)
Table 21. Transformer power ratings
Unit Size Power Rating
150 - 200 tons 340 kVA
225-300 tons 470 kVA