Riello Condexa PRO 100, Инструкция по установке, техническому обслуживанию и ремонту

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81
COMMISSIONING AND MAINTENANCE
171 defines the time (from the start of the request) from
which the setpoint modulation is started
176 defines the proportional term for setpoint modulation
177 defines the integrative term for setpoint modulation
6.6 Parameter 148: operating mode of the
cascade
It is possible to adopt cascade management which can be mod-
ified according to different strategies. These different strategies
can be set using the parameter known as "Cascade mode" Par.
148.
6.6.1 Par 148 = 0
The start-up/shutdown law of each module is based on the fol-
lowing graph.
The shut-off values of the lines with the y axis are the sum or
the difference of the values of the corresponding parameter in
relation to the value of the setpoint sent by the Manging module
to the modules.
Setp + Par 146
Clear Demand
(no time)
Remove Depending faster
Time = Par 143
Remove depending
Time = Par 76
Power Balance
Add Depending
Time = Par 75
Add Depending faster
Time = Par 142
Setp + Par 145
Setp - Par 144
Setp + Par 78
Setpoint
Setp - Par 77
-1
-1
-1
+1
-1
+1
-1
+1
-1
+1
-1
-1
-1
+1
-1
+1
-1
+1
-1
+1
-1
-1
-1
+1
-1
+1
-1
+1
-1
+1
-1
+1
-1
+1
-1
+1
-1
-1
-1
+1
Six bands are defined on the basis of the temperature read (by
the Managing module) on the delivery manifold of the primary
system.
− In the central band Power balance , defined (by the var-
iable parameters) around a setpoint, no start-ups or
shutdowns of the Depending modules are envisaged.
The parameters which define this band are 77 and 78.
− In the band Remove dependent and Add dependent ,
the start-ups and shutdowns are carried out with "long"
time intervals which can differ between start-up and
shutdown.
The parameters which define this band are 77, 78, 144,
145. The time interval is defined by parameters 75 and
76.
− In the band Remove dependent Faster and Add depend-
ent Faster , start-ups and shutdowns are carried out with
a "short" time interval which, even in this case, can differ
between start-up and shutdown. The shutdown band is
between the values of parameters 146 and 145, while the
start-up band is below the value defined by parameter
144. The time range is defined by parameters 142 and 143.
− In the band Clear demand , all the thermal modules are
immediately stopped. This band is above the value de-
fined by parameter 146.
6.6.2 Par 148 = 1
In this mode the system manages the cascade so that the min-
imum number of modules is on.
The first difference in relation to mode 0 refers to the logic with
which the modulation of Depending modules within the cas-
cade is managed.
In fact, while each thermal module modulates with its own PID
in mode 0, no more than two Depending modules modulate
with the same criteria in mode 1, while the remaining modules
operate at maximum power. The diagram is represented in the
following figure:
Managing
Managing
PID
PID
100%
100% 100%
100% 100% 100%
PID
PID PID
PID PID
PID PID
Managing
Managing
Managing
Practically speaking, if more than two thermal modules are on,
only two thermal modules are controlled via PID, while the oth-
ers receive a signal to move to maximum power.
The second difference refers to the start-up/shutdown rules of
the individual modules.
In any case, the start-up and shutdown rules are managed ac-
cording to the indications shown in the previous graph. The dif-
ference is that it is also possible to have start-ups/shutdowns of
the Depending modules in the "balancing" zone.
This additional start-up criteria (valid in the balancing band
only) ensures that a module is started-up when any one of
the two modules controlled by a PID adjustment has reached
a threshold power (Par 82) once a specific wait time defined by
Par 75 has elapsed.
Similarly (still within the balancing band), a module is shut-
down if both modules controlled by a PID adjustment have
reached a percentage of power which is below the minimum
power threshold (Par 83) once a specific wait time defined by
Par 75 has elapsed.