Control Temperature
The “Control Temperature” is dened as the unit temperature
input used to make the heat/cool changeover decision. This
determines whether or not cooling or heating is enabled.
The user may select Space Temperature, Return Temperature,
Outdoor Air Temperature or None for DAT units. Normally
either the Return or Space Temperature is selected as the
control temperature. Outdoor Air Temperature may be used as
the control temperature for DAT units, but not for Zone Control
units.
When the Control Temperature Source is set to None, the unit
no longer “changes over” between heating and cooling in the
normal manner. Instead it acts as if it is always in the “cooling”
mode of operation controlling to the discharge air cooling set
point. In this case the unit operating state will vary between
Cooling, Fan Only and Min DAT (heating) in order to maintain
the discharge air cooling set point. The unit will only enter the
Heating operating state and control to the discharge heating
set point for morning warm up purposes.
The Control Temperature Source automatically reverts from
Return to Space if both of the following are true:
• The Return Air Sensor is not present and reliable
• A network or local Space Sensor is present and reliable
The Control Temperature Source automatically reverts from
Space to Return if both of the following are true:
• The space sensor is not reliable (a valid space
temperature value is not provided via the network and
the space temperature sensor is either in alarm or not
present)
• The return air sensor is reliable (present and not in alarm)
The Control Temperature Source automatically reverts from
either Outdoor Air or Mixed Air to Return if the Control Type
is Zone (Not DAT). If the return air temperature is not reliable,
the control temperature may then revert to space as described
above.
The Control Temperature Source automatically reverts from
Mixed Air to Outdoor Air if Unit Type is not SCU.
A Control Temperature Fault that shuts down the unit is
initiated if any of the following is true.
• The return air sensor is not present and reliable and
Return Air is selected as the control temperature and a
space sensor is not available.
• A network or local space sensor is not present and
reliable and Space is selected as the control temperature
and a return temperature sensor is not available.
• The OAT Sensor is not present and reliable and Outdoor
Air is selected as the control temperature
• The mixed air temperature sensor is not present
or reliable and Mixed Air is selected as the control
temperature
Occupied Temperature Set Points
(See page 41 for more information)
When the Use Tstat set point parameter is set to No, the
Occupied Cooling Set Point and the Occupied Heating Set
Point may be set through the keypad or via a network signal.
In this case these set points are changed whenever the
network or keypad value changes. When the Use Tstat set
point parameter is set to Yes these set points can only be
adjusted through the zone thermostat. Heating and cooling set
points must not overlap. The Occupied Heating Set Point must
be equal to or less than the Occupied Cooling Set Point. If a
conict occurs from values entered via the keypad or network,
the Occupied Heating Set Point is automatically adjusted down
to eliminate the conict. When the Occupied Cooling Set point
is changed by more than 0.5 degrees through the wall mounted
sensor, the Occupied Heating Set Point is raised or lowered
the same amount so that the difference between the Cooling
and Heating set points does not change.
OAT Lockout
On heat pump units, compressor heating (primary heat) is
disabled whenever the outdoor air temperature is below the
Low Outdoor Air Ambient Heating Lockout set point or above
the High Outdoor Air Ambient Heating Lockout set point.
Whenever the outdoor air temperature rises above the Low
Outdoor Air Ambient Heating Lockout set point or falls below
the High Outdoor Air Ambient Heating Lockout set point
by more than the Heating Lockout Differential, compressor
heating operation is re-enabled.
Supplemental heating (secondary heat) is disabled whenever
the outdoor air temperature is above the High Outdoor Air
Ambient Supplemental Heating Lockout Set Point. Whenever
the outdoor air temperature falls below the High Outdoor Air
Ambient Supplemental Heating Lockout Set Point by more
than the Heating Lockout Differential, supplemental heating
operation is re-enabled.
Compressor cooling operation is disabled whenever the
outdoor air temperature falls below the Low Outdoor Air
Ambient Cooling Lockout Set Point. Whenever the outdoor
air temperature rises above the Low Outdoor Air Ambient
Cooling Lockout Set Point by more than the Cooling Lockout
Differential, compressor cooling operation is re-enabled.
On non-heat pump units, heating is disabled whenever
the outdoor air temperature is above the High Outdoor Air
Ambient Heating Lockout Set Point. Whenever the outdoor
air temperature falls below the High Outdoor Air Ambient
Heating Lockout Set Point by more than the Heating Lockout
Differential, heating operation is re-enabled.
Compressor cooling operation is disabled whenever the
outdoor air temperature falls below the Low Outdoor Air
Ambient Cooling Lockout Set Point. Whenever the outdoor
air temperature rises above the Low Outdoor Air Ambient
Cooling Lockout Set Point by more than the Cooling Lockout
Differential, compressor cooling operation is re-enabled.
OM 1141-3 • MICROTECH UNIT CONTROLLER 98 www.DaikinApplied.com
operator’s guIde
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