Pixsys ATR 421, User Manual

Page: 26 / 108

26 ATR 421 - User manual
NB . setting
dis.
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 confi 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-
fi gured as
cooL
. Command output must be connected to actuator responsi-
ble for heating action, while alarm will control the cooling action.
Parameters to confi 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 confi 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 confi gured
(
ou.d.b.
≤ 0), viceversa an overlapping will be confi gured (
ou.d.b.
> 0).
Figure below shows an example of double action PID (heating-cooling)
with
t.i.
= 0 and
t.d.
= 0.