CHAPTER 4 APPLIED OPERATIO N
E5EK
4--2
4.1 Selecting the Control Method
When selecting the control method, set the parameters according to the
following table. (Parameters are factory-set to heating control.)
Parameter
Control
Method
Control output 1
assignment
Control output 2
assignment
Direct/Reverse
operations
Heating control
(Standard)
Control output (heat)
-
Reverse operation
Cooling control
(Standard)
Control output (heat)
-
Direct operation
Heating and cooling
control
Control output (heat) Control output (cool) Reverse operation
For details on how to assign outputs, see 3.3 Setting Output Specifica-
tions (page 3 -6).
• When heating and cooling control is selected, the “deadband” and
“cooling coefficient” parameters can be used.
The dead band is set with the set point as its center. The dead band
width is the set value of the “dead band” parameter (level 1 mode). Set-
ting a positive value produces a dead band, while setting a negative
value produces an overlap ban d.
0
PV
0
PV
Output Output
Dead band: dead
band width = positive
Overlap band: dead
band width = negative
Heating
side
Heating
side
Cooling
side
Cooling
side
Set point Set point
If the heating and cooling character istics of the control target greatly
differ, preventing satisfactory control characteristics from being
obtained by the same PID parameters, adjust the proportional band (P
at cooling side) using the cooling coefficient to balance control between
the heating and cooling sides. In heating and cooling control, P at the
heating or cooling side is calculated by the following formula:
Heating side P = P; Cooling side P = cooling coefficient ¢ P
• In heating and cooling control, the manipulated variable output that
is output when controller operation is stopped is dependent on the set
value of the “MV at stop” parameter (level 2 mode) in the same way as
for standard control.
• However, note that in heating and cooling control, the manipulated
variable at the cooling side is treated as a negative value for the sake
of convenience. When the manipulated variable at STOP is a negative
value, the manipulated variable is output to only the cooling side, and
when a positive value, the manipulated variable is output to only the
heating side. The factory setting is “0”. If the controller is operated
using the factory setting, the manipulated variable is not output to
both the heating and cooling sides.
When the overlap band is set, the bumpless function that operates when switch-
ing between manual and automatic operation may not work.
Switching with
Manual operation
JHeating and
cooling control
F Dead band
F Cooling coeffi-
cient
F Manipu lated vari-
able at sto p
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