Daikin Magnitude WME106CD - Leaving Water Temperature (LWT) Reset

IOM 1266-2 • MAGNITUDE
®
MODEL WME CHILLERS 34 www.DaikinApplied.com
operaTIon
Figure 40: Settings View - Water
Table 13: Water Setpoints
Description Default Range PW Comments
Maximum Reset Delta T 0.0°F 0.0 to 20.0°F O
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 O Sets evaporator Delta T below which Return reset begins.
LWT Reset Type None
None
Return
4-20 mA
O
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 2 to 10.0°F O Sets amount leaving water must go above for rst compressor to start.
Shutdown Delta T 3.0°F 2 to 6.0°F O Sets amount leaving water must drop below setpoint for last compressor to stop.
Leaving Water Temp - Cool 44.0°F 38.0 to 75.0°F O
Sets control target for evaporator leaving water temperature in COOL mode. 36 °F is lowest
setpoint for shutdown.
Leaving Water Temperature (LWT) Reset
The Active Leaving Water variable shall be set to the current
Leaving Water Temperature (LWT) setpoint unless modied by
one of the reset methods below. (The current LWT setpoint is
Cool LWT as determined by the chiller mode.) The type of reset
in effect is determined by the LWT Reset Type setpoint.
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.
Reset Type – 4-20 mA
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 41; temperatures are examples only.
Figure 41: 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