Daikin WGZ030DW Operating And Maintenance Manual page 33

Parameters used:
1. Heating Leaving Water Temperature set point (Heat LWT)
2. Heating Maximum Reset set point (Htg MaxRes)
3. LWT Reset signal 4-20mA
Reset is 0ºF and the active leaving water set point is equal to the Heat 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 Heat LWT minus 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 mA reset in Heat mode is shown below.
Reset Type = Return (only for TGZ unit, Refrig = R134a)
Cooling Mode
The Active Cooling Leaving Water set point is adjusted based upon the difference between the chiller's
entering and leaving evaporator water temperatures.
Evap LWT (+) Clg MaxRes
'Active'
Evap LWT
Set Point
The active cooling leaving water set point is reset using the following parameters:
1. Evaporator Leaving Water Temperature set point (Evap LWT)
2. Cooling Maximum Reset set point (Clg MaxRes)
3. Cooling Start Reset Delta Temperature (Clg StrtResDT)
4. Evaporator Delta Temperature (evaporator entering water temperature minus leaving temperature)
Reset is accomplished by changing the Active Cooling Leaving Water set point from the Evap LWT set
point to the sum of Evap LWT (+) Cooling Maximum Reset set points as the evaporator delta temperature
(entering minus leaving) varies from the Cooling Start Reset Delta T set point towards 0º F delta
temperatures.
Heating Mode
The Active Heating Leaving Water set point is adjusted based upon the difference between the chiller's
entering and leaving condenser water temperatures.
OMM 1130-2
(54ºF)
Clg MaxRes set point
(range of reset action)
(10ºF)
Evap LWT set point
(44ºF)
Cooling Mode Return Reset
0ºF Clg StrtResDT setpoint
Evaporator Delta Temperature
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