Daikin BACnet Series User Manual

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PID Control Loops
A PID control loop calculates an error value from the dierence
between the measured room temperature and the acve setpoint.
The error value is expressed as a percentage and is typically used in a
BAS controller to control the state of an output. When the dierence
between the setpoint and room temperature is large, the error is large.
As the system reduces the dierence between the setpoint and space
temperature, the error becomes smaller. In a simple example, if the
output of the PID loop that is controlling a modulang valve is 50% the
valve would be opened half way; if the output of the loop is 100% the
valve posion is fully open.
The BACnet™ Thermostat heang and cooling PID loops are
implemented in all models.
The BACnet Thermostat uses a PID loop for the discharge air
temperature. The discharge air loop controls the posion of the
economizer. For this loop the setpoint is the measured temperature
of the air that is discharged by a roof top or heat pump unit.
The PID loops in the BACnet Thermostat are standard BACnet objects.
Staged Heang and Cooling for Rooop
and Heat Pump Units
Staged heang and cooling is used for applicaon other than chilled or
hot water systems. Typically the BACnet Thermostat controls gas heat,
electric heat, or direct expansion (DX) cooling with stage heang and
cooling. Staged cooling or heang can be mixed with a modulang valve
for cooling or heang.
Staged Cooling
As the demand for cooling increases, the BACnet Thermostat starts the
rst stage of cooling when the cooling PID loop rises above 95% and
the rst stage of cooling has been turned o for at least the me set by
the value of MINIMUM OFF TIME. The second stage of cooling is turned
on when the cooling loop rises above 99% and the rst stage has been
turned on for the period set by STAGE DELAY and the second stage has
been turned o for at least as long as the value of MINIMUM OFF TIME.
As the demand for cooling is sased, the second stage is turned o
when the cooling PID loop drops below 50%. This rst stage is turned
o when the cooling loop drops below 5%.
Staged Heang
As the demand for heang increases, the BACnet Thermostat starts the
rst stage of heang when the heang PID loop rises above 95%.
The second stage of heang is turned on when the heang loop rises
above 99% and the rst stage has been turned on for the period set by
STAGE DELAY.
As the demand for heang is sased, the second stage is turned o
when the heang PID loop drops below 50%. This rst stage is turned
o when the heang loop drops below 5%.
Sequences of Operaon

Daikin BACnet Series Specifications

General

Brand	Daikin
Model	BACnet Series
Category	Thermostat
Language	English