46
AC-SVX001A-EN
Custom Tab of the Configuration View within Tracer
TU.
IImmppoorrttaanntt:: For proper unit operation, BOTH the EDLS
and ECWS settings MUST be the same (2-
10 VDC or 4-20mA), even if only one input
is to be used.
The J23 and J26 terminal is chassis grounded and
terminal J2 1 and J24 can be used to source 12 VDC.
The ECLS uses terminals J22 and J23. ECWS uses
terminals J25 and J26. Both inputs are only compatible
with highside current sources.
Figure 23. Wiring examples for EDLS and ECWS
Chilled Water Reset (CWR)
UC800 resets the chilled water temperature set point
based on either return water temperature, or outdoor
air temperature. Return Reset is standard, Outdoor
Reset is optional.
The following shall be selectable:
• One of three Reset types:None, Return Water
Temperature Reset, Outdoor Air Temperature
Reset, or Constant Return Water Temperature
Reset.
• Reset Ratio setpoints: For outdoor air temperature
reset there shall be both positive and negative reset
ratios.
• Start Reset Setpoints.
• Maximum Reset setpints.
The equations for each type of reset are as follows:
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CWS' = CWS + RATIO (START RESET - (TWE - TWL))
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
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CWS' = CWS + RATIO * (START RESET - TOD)
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
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• CWS' is the new chilled water set point or the "reset
CWS"
• CWS is the active chilled water set point before any
reset has occurred, e.g. normally Front Panel,
Tracer, or ECWS
• RESET RATIO is a user adjustable gain
• START RESET is a user adjustable reference
• TOD is the outdoor temperature
• TWE is entering evap. water temperature
• 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.
Reset Type Range Reset Ratio
Start Reset Max Reset Increment
Factory Default
Return 10 to 120%
4 to 30°F
(2.2 to 16.7 °C)
0 to 20°F
(0.0 to 11.1°C)
1% 50%
Outdoor 80 to -80%
50 to 130°F
(10 to 54.4°C)
0 to 20°F
0.0 to 11.1°C)
1% 10%
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 Delta Temp.
• MAXIMUM RESET = Design Delta Temp.
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
IInnssttaallllaattiioonn EElleeccttrriiccaall
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