Operation
www.DaikinApplied.com 47
IOM 1281-2 • CENTRIFUGAL WATER CHILLERS
Reset Type – 4-20mA
The Active Leaving Water variable is set equal to the Cool LWT
setpoint if the reset signal is less than or equal to 4 mA. It is set
equal to (Cool LWT se Max Reset Delta T setpoint) if
the reset signal equals or exceeds 20 mA. The Active Leaving
Water variable will vary linearly between these extremes if the
reset signal is between 4 mA and 20 mA. An example of this
action is shown in
Figure 49
; temperatures are examples only.
Figure 49: LWT Reset (Cool Mode)
Figure 50:
Settings View - Modes
Table 13: Modes Setpoints
Description
Default
Range
PW
Comments
Chiller Model
WCF
WCF, WMC
T
WCF is the general software model for WDC, WCC and TDC
WCC Enable
Disabled (other)
Enabled (WCC), Disabled (other) T
Will always be Disabled for WDC chillers
Unit Enable
OFF
OFF, AUTO
O
OFF: everything is off. AUTO: evap pump on, comp, cond pump and tower on
as required to meet LWT
Control Source
Switches
Switches, Local, Network BAS
O
Sets control source. See
Figure 35 on page 37
Available Modes
Cool with Glycol
Cool Only, Cool w/ Glycol, Cool/
Ice w/ Glycol, Ice Only w/ Glycol,
Cool/Heat, Heat Only
M
See Water Setpoints,
Table 12
, for control temperature targets for each mode
No. of Compressors
2
1 to 2
T
Models will be set to 2 as a default.
Max Compressors On
2
0 to 8
M
Max number of compressors that can be on local pLan chiller network
HATS - Starting
Off
Off, Chiller, System
M
High Ambient Tandem Start
Condenser Pump
Pump #1 Primary
Pump #1 Only, Pump #2 Only,
Auto Lead, #1 Primary, #2
Primary
M
Pump #1 Only, Pump #2 Only, use only these pumps AUTO, balance hours
between #1 and #2 #1 Primary, #2 Primary, if primary fails, use other
Evaporator Pump
Pump #1 Primary
Pump #1 Only, Pump #2 Only,
Auto Lead, #1 Primary, #2
Primary
M
Pump #1 Only, Pump #2 Only, use only these pumps AUTO, balance hours
between #1 and #2 #1 Primary, #2 Primary, if primary fails, use other
Stage Mode
Normal
Normal, Hi Eff, Pump, Standby
M
Normal - Fixed sequence and /or balance starts/hours. Hi Eff - Starts
compressor on each dual compressor chiller first Pump - Starts all
compressors on one chiller first. Standby - Use compressor only if another
fails.
Stage Sequence
1
0-99
M
Sets fixed sequence for compressor staging
Hot Gas Mode
RLA
Off, Water, RLA
T
Hot Gas Control Point
20%
20 to 70%
T
Sets hot gas control point %
4 ma
20 ma
Cool LWT Setpoint
(44.0°F)
Max Reset Delta T
(10.0°F)
(54.0°F)
0 ma
