Daikin WGZ030DW, Operating And Maintenance Manual

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32 WGZ030D through WGZ200D OMM 1130
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The Stage Down temperature is calculated as:
Stage Down Temperature = Heat LWT + (Control Band/2)
The Heat 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 Tempe Shutdown Delta Temperature
Leaving Water Temperature (LWT) Reset
The active leaving water set point is set to the current Leaving Water Temperature (LWT) set point unless
the unit is in either cool or heat mode and any of the reset methods below are selected. The type of reset
in effect is determined by the LWT Reset Type set point.
Reset Type = NONE
The Active Leaving Water Temperature set point is set equal to the current LWT set point. IN cool mode,
this will be Evap LWT and in heat mode this will be Heat LWT.
Reset Type = 4-20 mA
The Active Leaving Water set point is adjusted by the 4 to 20 mA reset analog input.
Cooling Mode
The Active Leaving Water set point is adjusted by the 4 to 20 mA reset analog input.
Parameters used:
1. Evaporator Leaving Water Temperature set point (Evap LWT)
2. Cooling Maximum Reset set point (Clg MaxRes)
3. LWT Reset signal 4-20mA
Reset is 0ºF and the active leaving water set point is equal to the Evap LWT set point if the reset signal is
less than or equal to 4 mA. Reset is equal to the Max Reset set point and the active leaving water set
point is equal to the Evap LWT plus Max Reset set points if the reset signal equals or exceeds 20 mA.
The amount of reset will vary linearly between these extremes if the reset signal is between 4 mA and 20
mA. An example of the operation of 4-20 reset in Cool mode is shown below.
Cooling Mode 4-20mA Reset
Clg MaxRes set point
Evap LWT set point
20mA
(range of reset action)
Reset Signal mA
(54ºF)
(10ºF)
(44ºF)
4mA
‘Active’
Evap LWT
Set Point
Evap LWT (+) Clg MaxRes
Heating Mode (only for TGZ unit Refrig = R134a)
The Active Leaving Water set point is adjusted by the 4 to 20 mA reset analog input.