26 ATR 421 - User manual
NB. setting di s . on parameter 44 FE.Po the valve DOESN’T works with feed-
back : it is necessary to set the valve time on parameter 43 uAL.t.
8.7.1 Heating / Cooling PID
ATR421 is suitable also for applications requiring a combined heating-coo-
ling P.I.D. action.
Command output has to be con gured as heating PID (Act. t. = Heat and
p. b . greater than 0), and one of alarms (AL.1, AL.2, AL.3 or AL.4) has to be con-
gured as
cooL. Command output must be connected to actuator responsi-
ble for heating action, while alarm will control the cooling action.
Parameters to con gure for heating PID are:
act. t. = Heat Command output action type (Heating)
p. b . : Proportional band heating
t.i. : Integral time Heating and cooling
t.d . : Derivative time Heating and cooling
t.c. : Cycle time Heating
Parameters to con gure for cooling PID are (example: action associated to
alarm 1):
AL.1 = cooL Alarm1 selection (Cooling)
P. b . m . : Proportional band multiplier
ou.d.b. : Overlapping / Dead band
co.c.t. : Cycle time Cooling
Parameter p. b . m . (that ranges from 1.00 to 5.00) determinates the proportio-
nal band for cooling action, according to the formula:
- Proportional band for cooling action: = p. b . * p. b . m .
In this way it is possible to have a proportional band for cooling action
that will be equal to heating proportional band if p. b . m . = 1.00, or 5 times
greater if p.b . m . = 5.00.
- Integral and Derivative time are the same for both actions.
Parameter ou.d.b. establishes the overlapping (in percentage) betwe-
en the two actions. For installations where heating and cooling outputs
cannot be activated at the same time, a Dead band will be con gured
(ou.d.b. ≤ 0), viceversa an overlapping will be con gured (ou.d.b. > 0).
Figure below shows an example of double action PID (heating-cooling)
with t.i. = 0 and t.d. = 0.
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