IM 1234-1 • BACNET THERMOSTAT 30 www.DaikinApplied.com
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Fan Control for Rooftop and Heat
Pump Units
A user with Password 1 can set the BACnet Thermostat
controlled fan to either run continuously or to start
automatically on a call for cooling or heating.
Auto
– When Auto is selected, the fan runs only when there is
a call for heating or cooling. It continues to run for the period
set by the fan delay timer after the call for heating or cooling.
ON
– The fan will run continuously regardless of the heat/cool
modes or occupied state.
Economizer Cooling for Rooftop
and Heat Pump Units
Some models of the BACnet Thermostat include programming
for an economizer. This programming controls an economizer
outside air damper connected to the output terminal (ECON).
NOTE:
The economizer can be enabled only if outside air
temperature and discharge air temperature sensor
are connected to the BACnet Thermostat.
The economizer mode is enabled for cooling when the outside
air temperature (OAT) is 2°F below the value of the limit set
by Economizer Enable Temperature and disabled if the OAT is
2°F above the value of Economizer Enable Temperature.
Once enabled, the economizer outside air damper opens to
the larger value of either the minimum damper position limit
(Minimum Econ Damper) or the Discharge Air Temperature
loop. The Discharge Air Temperature loop modulates from
0% to 100% as the Discharge Air Temperature rises above
the Discharge Air Temperature setpoint. The Discharge Air
Temperature setpoint resets between room temperature
and the limit for minimum discharge air temperature as the
cooling loop varies between 0 and 50%. If the Discharge Air
Temperature decreases below 55°F, the Outside Air Damper
returns to the minimum damper position.
Heat Pump Unit Specific Functions
The heat pump unit fan and staging is similar to the roof top
unit fan and staging principles.
Reversing Valve Action
The BACnet Thermostat reversing valve output (O/B) is
energized on a call for cooling (‘O’ function). The action can
be changed from the user interface to be active on a call for
heating (‘B’ function). The ‘O’ function is the default.
Auxiliary or Emergency Heat Action
The heat pump unit AUX/E output is for auxiliary or emergency
heat. Operation can be configured for one of three modes.
Compressor lockout
– The AUX/E output is active only on a
call for heating when the compressors are locked out because
the outside air temperature has dropped below the value of
the Compressor OAT Low Limit. The lockout is cleared when
the outside air temperature rises 2°F above the value of
Compressor OAT Low Limit.
Third stage
– The AUX/E output functions as the output for a
third stage of heat.
None
– This function is a manual operation that can only be
turned on from the user interface. When emergency heat is
turned on, the AUX/E output is used to maintain the active
heating setpoint and both compressor outputs are locked-out.
