User manual -
ATR144- 25
8.9
Dual Action (Heating-Cooling)
ATR144 is suitable also for systems requiring a combined
heating-cooling action.
The command output has to be configured as PID for Heating
(Par. 19
ac.t.1
=
Heat
and
P.b. 1
greater than 0), and one of the
alarms (
AL.1.F.
or
AL.5.F.
) has to be configured as
cooL.
The command output must be connected to the actuator
responsible for heating, while the alarm will control cooling
action.
Parameters to be configured for the heating PID are:
ac.t.1
=
Heat
Command output action type (Heating);
P.b. 1
or
p.b. 2
: Heating proportional band;
i.t. 1
or
i.t. 2
: Integral time of heating and cooling;
d.t. 1
or
d.t. 2
: Derivative time of heating and cooling;
c.t. 1
or
c.t. 2
: Heating time cycle.
Parameters to be configured for the cooling PID related to
regulation loop 1 and alarm 1 are:
AL.1.F.
=
cooL.
Alarm 1 selection (Cooling);
p.b.m.1
: Proportional band multiplier;
o.d.b.1
: Overlapping / Dead band;
c.c.t.1
: Cooling time cycle.
Par.
p.b.m.1
(that renges from 1.00 to 5.00) determines the
proportional band of
cooling action basing on the formula:
Proportional band for cooling action
=
p.b. 1
x
p.b.m.1.
This gives a proportional band for cooling which will be the
same as heating band if
p.b.m.1
= 1.00, or 5 times greater if
p.b.m.1
= 5.00.
Integral and derivative time are the same for both actions
.
Par.
o.d.b.1
determines the percentage overlapping between
the two actions. For systems in which the heating output and
cooling output must never be simultaneously active a Dead
Band (
o.d.b.1
≤ 0), must be configured, vice versa you can
configure an overlapping (
o.d.b.1
> 0).
The following figure shows an example of dual action PID
(heating-cooling) with
i.t. 1
= 0 e
d.t. 1
= 0.