www.DaikinApplied.com 47 IOM 1274-3 • CENTRIFUGAL WATER CHILLERS
Figure 51: Settings View - Water
Figure 52: Water Setpoints
Description Default Range PW Comments
Maximum Reset Delta-T 0.0 °F 0.0 to 20.0 °F T
Reset Type = Return: Sets the maximum LWT reset that can occur.
Reset Type = 4-20 mA: Sets amount of reset at 20 mA input.
Start Reset Delta-T 10 °F 0.0 to 20.0 °F T Sets evaporator delta-T above which Return reset begins.
LWT Reset Type None
None
Return
4-20mA
T
Reset raises LWT setpoint
Return (uses start Reset Delta T & Max Reset Delta T)
4-20 mA (4 mA=None, 20 mA=Max as set by Max Reset Delta T)
Startup Delta-T 3.0 °F 0 to 10.0 °F T
units, set the temperature delta below leaving water for compressor to start.
Shutdown Delta-T 3.0 °F 0 to 3.0 °F T
Sets amount leaving water must drop below setpoint for last compressor to stop. For
Stage Delta-T 1.0 °F 0 to 9.9 °F M Sets amount leaving water must go above setpoint for next compressor to start.
Leaving Water Temp - Cool 44.0 °F 35.0 to 80.0 °F O
Sets control target for evaporator leaving water temperature in COOL mode. 35 °F is
lowest setpoint for shutdown.
Leaving Water Temp - Cool
w/ Glycol or Cool / Ice
44.0 °F 15.0 to 80.0 °F O
Sets control target for evaporator leaving water temperature in Cool with Glycol or Cool
/ ICE mode. When running in the ICE portion of the mode, the temperatures limit to the
lower range of 15-35 °F.
Leaving Water Temp - Ice 25.0 °F 15.0 to 35.0 °F O Sets control target for evaporator leaving water temperature in ICE mode.
Leaving Water Temp - Heat 135.0 °F 66.0 to 150.0°F O Sets control target for condenser leaving water temperature in HEAT mode.
No Start - Water Source 70 °F 30 to 100 °F O
Delta Reset - Water Source 55.0 °F 50 to 100 °F O
The Active Leaving Water variable shall be set to the current
by one of the reset methods below. (The current LWT setpoint
is Cool LWT as determined by the chiller mode.) The type of
(Setpoint 6 of the WATER Setpoint Screen).
Reset Type – NONE - The Active Leaving Water variable is set
equal to the current LWT setpoint.
Reset Type – RETURN - The Active Leaving Water variable
is adjusted by the return water temperature. When the chiller
mode = COOL, the Active Leaving Water variable is reset using
the following parameters:
1. Cool LWT setpoint
2. Max Reset Delta T setpoint
3. Start Reset Delta T setpoint
Reset is accomplished by changing the Active Leaving Water
variable from the (Cool LWT setpoint) to the (Cool LWT
setpoint + Max Reset Delta-T setpoint) when the evaporator
(return – leaving) water temperature delta varies from the (Start
Reset Delta-T setpoint) to 0.
- 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 setpoint
+ 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
53; temperatures are examples only.
Figure 53: LWT Reset (Cool Mode)
4 ma
20 ma
Cool LWT Setpoint
(44.0°F)
Max Reset Delta T
(10.0°F)
(54.0°F)
0 ma
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