User manual - ATR121 - 23
8.6
Dual action Heating-Cooling
The ATR121/141 is suitable also for systems requiring a
combined heating-cooling action. Command output must
be configured as Heating PID (par.11
reG.
=
Hea
and par. 15
p. b .
greater than 0), and one of the alarm must be configured
as cooling action (par. 19
AL.
=
coo
. Command output must
be connected to the actuator responsible for heating action
while the alarm output will control cooling action.
• Parameters to configure for the Heating PID are:
reG.
=
Hea
Command output type (Heating)
p. b .
: Heating proportional band
t .i .
: Integral time of heating and cooling
t. d.
: Derivative time of heating and cooling
t. c.
: Heating time cycle
• Parameters to configure for the Cooling PID are:
AL.
=
coo
: Alarm selection as cooling
p.b.m
: Proportional band multiplier
ou.d
: Overlapping/Dead band
t. c.2
: Cycle time for cooling output
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 .
*
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 time and derivative time are the same for both
actions.
Parameter
ou.d
determines the overlapping percentage
between the two actions. For systems in which the heating
and cooling output must never be simultaneously active a
dead band (
ou.d
≤ 0), can be configured, and viceversa an
overlapping (
ou.d
> 0):
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