Overlap/Dead Band Function - Mitsubishi Electric MELSEC iQ-R Series User Manual

1.6

Overlap/dead Band Function

In the heating-cooling control, the temperature process value (PV) significantly changes due to a slight heating or cooling
control output when the heat produced by a controlled object and natural cooling are being balanced. Consequently, an
excessive output may be executed.
The temperature where the cooling control output starts can be shifted using this function; therefore, whether control stability
is prioritized or energy saving is prioritized can be selected.
Overlap
The overlap refers to the temperature area where both of heating control and cooling control are executed. In the temperature
area where both heating and cooling output overlap, both of the outputs negate each other. Thus, the control gain becomes
moderate. Consequently, the variation amount in the temperature process value (PV) for the output becomes small, improving
control stability.
Ex.
When the following values have been set:
• "Input range setting" of "Control basic parameters" in "Application Setting": 38 (Temperature measuring range: -200.0 to
400.0)
• "Target Value(SV) Setting" of "Control basic parameters" in "Application Setting": 200.0
• "Overlap/dead band setting" of "Heating/cooling control setting" in "Application Setting": -15.0
The range of 185.0 to 200.0 is the overlapping area.
The temperature where a cooling operation starts = (Set value (SV)) - 15.0 = 185.0
As shown below, shifting the temperature where a cooling operation starts to the lower temperature side of the set value (SV)
produces an overlapping area. (The following is an example of when the module is in P control.)
Heating only
(manipulated value for cooling (MVc): 0%)
100%
0%
Cooling starts at 185.0
-100%
In the Q compatible mode, set -2.5% for "Overlap/dead band setting" of "Heating/cooling control setting" in
"Application Setting." (400 - (-200))  (-0.025) = -15
Heating/Cooling
Heating
.
Cooling only
(manipulated value for heating (MVh): 0%)
Set value (SV) is 200.0 .
Cooling
1.6 Overlap/dead Band Function
1
1 FUNCTIONS
29