Discharge Air Temperature
Setpoint Reset - Heating
The Heating DAT Setpoint may be reset for units with DAT
Heating Control. The Discharge Air Temperature Setpoint
will never be set below the Minimum DAT Heating Setpoint
or above the Maximum DAT heating Setpoint on the Heating
Reset menu. The reset type may be set to one of the following:
• None: Discharge Heating Spt is user adjustable
• Network: Discharge Heating Spt is equal to the Network
DAT Htg Setpoint when it is valid
• Space: Discharge Heating Spt is based on the Space
Sensor
• Return: Discharge Heating Spt is based on the Return Air
Sensor
• OAT: Discharge Heating Spt is based on the Outdoor Air
Temperature
• Ext mA: Discharge Heating Spt is determined by a 0-20
or 4-20 mA signal
• Ext V: Discharge Heating Spt is determined by a 0-10 or
2 - 10 VDC signal
Reset reverts from Return to None when the return air sensor
opens or shorts. Reset reverts from Space to None when the
space sensor opens or shorts. Reset reverts from OAT to None
when the outdoor air sensor opens or shorts.
When Space, Return, OAT, Ext mA, or Ext V is selected, the
Discharge Heating Spt equals the Max Htg Spt when the
selected value equals the Max Htg Spt @ value. Similarly,
the Discharge Heating Spt equals the Min Htg Spt when the
selected value equals the Min Htg Spt @ value.
When Space, Return, or OAT is selected, the reset schedule
should be set so that the DAT Heating setpoint decreases as
the selected temperature increases as shown in the graph
below.
When Ext mA is selected, the values “Min Htg Spt @” and
“Max Htg Spt @” are entered as mA values. When Ext VDC is
selected, the values “Min Htg Spt @” and “Max Htg Spt @” are
entered as VDC values.
If Ext mA or Ext V is selected as the type of reset, the Min Htg
Spt @ value may be set above the Max Htg Spt @ value to
cause a decrease in the DAT setpoint as the external signal or
the Min Htg Spt @ value may be set below the Max Htg Spt @
value to cause an increase in the DAT setpoint as the external
signal increase.
When ever the Clg Reset Type or Engineering Units is
changed, the Min Clg Spt @ and Max Clg Spt @ values revert
to default values as follows:
• None: Min Clg Spt @=0NA, Max Clg Spt @=100NA
• Network: Min Clg Spt @=0NA, Max Clg Spt @=100NA
• Space, Return: Min Clg Spt @=73.0F, Max Clg Spt
@=71.0F
• OAT: Min Clg Spt @=90.0F, Max Clg Spt @=70.0F
• ExtmA: Min Clg Spt @=4.0mA, Max Clg Spt @=20.0mA
• ExtVDC: Min Clg Spt @=0.0V, Max Clg Spt @=10.0V
An example of discharge temperature reset based on outdoor
air temperature is illustrated in Figure 20 (Cooling Reset Type
Flag is set to “OAT” in this example). When the current outdoor
air temperature is greater than or equal to the Minimum
Cooling Set Point Reset Value (90°F in this example), the
Discharge Cooling Set Point is set equal to the Minimum
Discharge Cooling Set Point (55°F in this example). This is
shown as Point C in Figure 20. When the current outdoor air
temperature is less than or equal to the
Maximum Cooling Set Point Reset Value (70°F in this
example), the Discharge Cooling Set Point is set equal to the
Maximum Discharge Cooling Set Point (65°F in this example).
This is shown as Point A in Figure 20. When the current
outdoor air temperature is between the Minimum Cooling Set
Point Reset Value and the Maximum Cooling Set Point Reset
Value, the Discharge Cooling Set Point varies linearly between
the Minimum Discharge Cooling Set Point and Maximum
Discharge Cooling Set Point. This is shown as Point B in
Figure 20.
Figure 20: Discharge Temperature Reset Based on
Temperature
OM 1141-3 • MICROTECH UNIT CONTROLLER 110 www.DaikinApplied.com
operator’s guIde
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