User manual

26 - UR4848 - User manual UR4848 - User manual - 27
Lc.n.c. : With open input allows to lock the reading of sensors;
tune : Enables / disables Tuning function if parameter 57 tune is selected as
man. ;
a.ma.i. : If parameter 60 au.ma. is selected as en. or en.st. controller switch
from automatic to manual functioning;
a.ma.c. : If parameter 60 au.ma. is selected as en. or en.st. UR4848 works in
automatic mode if input is open or in manual mode if input is closed.
NB: The digital input functions are not available with sensors PT100 and NI100
on model UR484802.
7.13 Dual Action Heating-Cooling
UR4848 is suitable also for systems requiring a combined heating-cooling ac-
tion. Command output must be congured 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
congured as
cooL.
Command output must be connected to the actuator responsible for heat, whi-
le the alarm will control cooling action.
Parameters to congure 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 congure for the Cooling P.I.D. are the following (ex: action as-
sociated 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 si-
multaneously active a dead band (
ou.d.b. ≤ 0) can be congured, and vice versa
an overlapping (
ou.d.b. > 0).
The following gure shows an example of dual action P.I.D. (heating-cooling)
with
t.i. = 0 and t.d. = 0.
ACTIVE
ACTIVE
SPV
PV
p.b x p.b.m. (COOL - FREDDO)
au.d.b. < 0
p.b (HEAT - CALDO)
COMMAND OUTPUT (HEAT - CALDO)
ALARM OUTPUT (COOL - FREDDO)
SPV
PV
ACTIVE
ACTIVE
p.b x p.b.m. (COOL - FREDDO)
au.d.b. = 0
p.b (HEAT - CALDO)
COMMAND OUTPUT (HEAT - CALDO)
ALARM OUTPUT (COOL - FREDDO)
SPV
PV
ACTIVE
ACTIVE
p.b x p.b.m. (COOL - FREDDO)
au.d.b. > 0
p.b (HEAT - CALDO)
COMMAND OUTPUT (HEAT - CALDO)
ALARM OUTPUT (COOL - FREDDO