Controller Operation - Daikin WGZ030DW Operating And Maintenance Manual

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 cooling 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
In heating mode, the Control Band is calculated as follows:
Control Band = Cond Delta Temperature Set Point * 0.3
Control Band = Cond Delta Temperature Set Point * 0.2
Control
Band
If the 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:
The Stage Down temperature is calculated as:
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 Up temperature is calculated as:
Stage Up temperature = Cool LWT + Control Band – (Cool LWT – 39.0
In all other Unit modes the compressor staging temperatures are calculated as shown below:
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 Shutdown 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:
OMM 1130-2
(Control Band/2)
Leaving Water Set Point
(Control Band/2)
Stage Up Temperature = Cool LWT + (Control Band/2)
Stage Down Temperature = Cool LWT – (Control Band/2)
Stage Down Temperature = Cool LWT – (Cool LWT - 39.0
Stage Up Temperature = Cool LWT + (Control Band/2)
Stage Down Temperature = Cool LWT – (Control Band/2)
Stage Up Temperature = Heat LWT - (Control Band/2)
Six compressor units
Four compressor units
Six compressor units
°
F)
°
F)
31