Daikin WGZ030DW - Controller Operation

OMM 1130-2 31
Controller Operation
Calculations
The Control Band defines the temperatures around the Controlling Leaving Water Temperature set point
where compressors will be staged on or off. In cool mode, the controlling leaving water temperature set
point will be Evap LWT. In heat mode, the controlling leaving water temperature set point will be Heat
LWT.
In c
ooling mode, the Control Band is calculated as follows:
Control Band = Evap Delta Temperature Set Point * 0.3 Four compressor units
Control Band = Evap Delta Temperature Set Point * 0.2 Six compressor units
In hea
ting mode, the Control Band is calculated as follows:
Control
Band = Cond Delta Temperature Set Point * 0.3 Four compressor units
Control Band = Cond Delta Temperature Set Point * 0.2 Six compressor units
If th
e Unit mode is Cool:
When the Cool Leaving Water Temperature set point is more than half the Control Band above
39.0° F the Stage Up temperature is calculated as follows:
Stage Up Temperature = Cool LWT + (Control Band/2)
The S
tage Down temperature is calculated as:
Stage Down Temperature = Cool LWT – (Control Band/2)
If the Cool Leaving Water Temperature set point is less than half the Control Band above 39.0° F the
Stage Down temperature is calculated as:
Stage Down Temperature = Cool LWT – (Cool LWT - 39.0
° F)
Stage U
p temperature is calculated as:
Stage Up temperature = Cool LWT + Control Band – (Cool LWT – 39.0
° F)
In all
other Unit modes the compressor staging temperatures are calculated as shown below:
Stage Up Temperature = Cool LWT + (Control Band/2)
Stage Down Temperature = Cool LWT – (Control Band/2)
The Cool
Start up and Shutdown temperatures are calculated from the Control Band. The Start Up
temperature determines when the first compressor on the unit will start. The Start Up temperature
calculation is shown below:
Start Up Temperature = Stage Up Temperature + Start Up Delta Temperature
The Shut
down temperature defines when the last running compressor will shutdown. The Shutdown
temperature calculation is:
Shutdown Temperature = Stage Down Temperature – Shutdown Delta Temperature
If the Unit mode is Heat:
Stage Up temperature is calculated as follows:
Stage Up Temperature = Heat LWT - (Control Band/2)
Leaving Water Set Point
Control
Band
(Control Band/2)
(Control
Band/2)