24 - DRR245 -
User manual
9.3
Dual Action Heating-Cooling
DRR245 is suitable also for systems requiring a combined heating-cooling
action. Command output must be configured as Heating P.I.D. (
Act.t.
=
HEAT
and with a
P.b.
greater than 0), and one of the alarms (
AL.1
,
AL. 2
or
AL. 3
) must
be configured as
cooL.
Command output must be connected to the actuator responsible for heat, while
the alarm will control cooling action.
Parameters to configure for the Heating P.I.D. are:
Act.t.
=
HEAT
Command output type (Heating);
P.b.
: Heating proportional band;
t.i
: Integral time heating and cooling;
t.d.
: Derivative time heating and cooling;
t.c.
: Heating time cycle.
Parameters to configure for the Cooling P.I.D. are the following (ex: action
associated to alarm 1):
AL.1
=
cooL
Alarm 1 selection (Cooling);
P.b.M.
: Proportional band multiplier;
ou.d.b.
: Overlapping / Dead band;
co.t.c.
: Cooling time cycle.
Parameter
p.b.m.
(that ranges from 1.00 to 5.00) determines the proportional
band of cooling basing on the formula:
Cooling proportional band
=
P.b.
x
P.b.M.
This gives a proportional band for cooling which will be the same as heating
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.
determines the percentage overlapping between the two
actions. For systems in which the heating and cooling output must never be
simultaneously active a dead band (
ou.d.b.
≤ 0) can be configured, and vice
versa an overlapping (
ou.d.b.
> 0).
The following figure shows an example of dual action P.I.D. (heating-cooling)
with
t.i.
= 0 and
t.d.
= 0.
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