Pixsys DRR460 Series, User Manual, Page: 13 / 72

User manual - DRR460 - 13
7.9 Dual Action Heating-Cooling
DRR460 is suitable also for systems requiring a combined heating-cooling action.The command
output has to be configured as PID for Heating (par. 33
p.b.
greater than 0), while the alarm 1 and 2 has
to be configured as Cooling (value 9 on par. 56
AL. 1
o par. 68
aL. 2
). 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:
p.b.
(word 2033): Heating proportional band
t.i.
(word 2034): Integral time of heating and cooling
t.d.
(word 2035): Derivative time of heating and cooling
t.c.
(word 2040): Heating time cycle
Parameters to be configured for the cooling PID are:
AL. 1
(word 2056) or
AL. 2
(word 2068) =
cooL
(value 9) Alarm selection (Cooling)
p.b.M.
(word 2042): Proportional band multiplier
ou.d.b.
(word 2043): Overlapping / Dead band
co.c.t.
(word 2044): Cooling time cycle
Par.
p.b.M.
(that ranges from 1.00 to 5.00) determines the proportional band of cooling action basing
on the formula:
Proportional band for cooling action =
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 and derivative time are the same for both actions.
The par.
ou.d.b.
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 (
ou.d.b.
≤ 0)
must be configured, vice versa you can configure 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.
ACTIVE
ACTIVE
SPV
PV

x

= COOL

x

=
COOL

x

=
COOL

< 0

= 0

> 0

( HEAT )

( HEAT )

( HEAT )
COMMAND OUTPUT (
HEAT
)
ALARM OUTPUT ( COOL )
COMMAND OUTPUT (
HEAT
)
ALARM OUTPUT ( COOL )
COMMAND OUTPUT (
HEAT
)
ALARM OUTPUT ( COOL )
SPV
PV
ACTIVE
ACTIVE
SPV
PV
ACTIVE
ACTIVE
ACTIVE
ACTIVE
SPV
PV

x

= COOL

x

= COOL

x

= COOL

< 0

=
0

> 0

( HEAT )

( HEAT )

( HEAT )
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT (
COOL
)
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT ( COOL )
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT ( COOL )
SPV
PV
ACTIVE
ACTIVE
SPV
PV
ACTIVE
ACTIVE
ACTIVE
ACTIVE
SPV
PV

x

= COOL

x

= COOL

x

= COOL

<
0

= 0

>
0

( HEAT )

( HEAT )

( HEAT )
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT ( COOL )
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT (
COOL
)
COMMAND OUTPUT ( HEAT )
ALARM OUTPUT (
COOL
)
SPV
PV
ACTIVE
ACTIVE
SPV
PV
ACTIVE
ACTIVE