Setting The Main Parameters; Par.73 - Managing, Stand-Alone, Dependent Mode; Par.147 - No. Of Boilers; Par.7 - Heating Setpoint Hysteresis - Riello Condexa PRO NA 75P Installation, Operation And Service Manual

SETTING PARAMETERS OF THE CASCADE SYSTEMS

6.1.1 Setting the main parameters

Some parameters are essential in order for the system to operate
in cascade and setting these parameters is a determining factor
for correct system operation.
6.1.2 Par.73 – Managing, Stand-alone, Dependent
mode.
Parameter 73 defines how the boiler is addressed and ensures
that the signal from the secondary sensor is recognized.
Three values can be set:
− Managing: to be set on the Managing boiler so that sec-
ondary sensor operation is activated.
NOTE: The secondary sensor SC must be connected to the 2nd
boiler (1st Depending boiler);
− Stand Alone: to be set on the Managing boiler so that sec-
ondary sensor operation is deactivated;
− 2 - 7 to be set on all Depending boilers.
Home/Menu
Settings
Boiler Settings
screen
6.1.3 Par.147 – No. of boilers
Parameter 147 serves to define the number of boilers present on
the system (it is important to set the number of boilers connected
in order to ensure correct system operation). This parameter must
only be set on the Managing boiler.
Home/Menu
Settings
Boiler Settings
screen
6.1.4 Par.7 – heating setpoint hysteresis
Parameter 7 adjusts shutdown of the individual boilers when the
setpoint is exceeded. With cascade operation, this value must be
increased (up to a maximum of 36 °F (20 °C) to prevent the boiler
operation from being disabled (since the default value is 9 °F (5 °C)
if the system decides to increase the setpoint based on the value
read on the primary or secondary sensor (see sections "General
operation", "Operation with the primary sensor" and "Operation
with the secondary sensor")
This parameter is to be modified (in the same way) on all boilers
of the cascade system (Managing boiler and all the relative De-
pending boilers).
Home/Menu
Settings
Boiler Settings
screen
Boiler Cascade (73) Stand
Settings Alone Boiler
Cascade (147) Number
Module Config. of Units
Boiler (7)
parameters Heat Hyst. Up
96

6.1.5 General operation

With a cascade system, the regulator of the managing boiler es-
tablishes a setpoint to be sent to the depending boilers based on
parameters 86-87, the difference between the setpoint value set
and the value read on the primary supply manifold (or on the ba-
sis of par 176-177 and the difference between the setpoint value set
and the value read on the secondary supply manifold).
On the basis of the setpoint received from the Managing boiler,
each boiler modulates based on its own PID (Par 16, Par 17 and Par
18) as a function of the difference between the setpoint (sent by
the Managing boiler) and the value read by the supply sensor on
the boiler itself.
9
The PID is a Proportional-Integral-Derivative control system
(abbreviated to PID) with retro-action. By reading an input
value which determines the current value, it is able to react in
the event of a positive or negative error (difference between
the current value and the target value), tending towards 0.
Reaction to the error can be regulated through the terms
"proportional, integral, derivative".

6.2 Operation with the primary sensor

The system sensor present on the primary system (see block dia-
grams 1 and 3) allows the setpoint sent to the individual boilers to
be modulated on the basis of the difference between the setpoint
and the value read on the supply manifold of the primary system.
The following parameters regulate this modulation:
79 defines the maximum setpoint decrease
80 defines the maximum setpoint increase
81 defines the time (from the start of the request) from which
the setpoint modulation is started
86 proportional parameter for setpoint modulation
87 integrative parameter for setpoint modulation

6.3 Operation with the secondary sensor

When the secondary system is present (see block diagrams 2 and
4), the setpoint sent to the individual boilers to be modulated on
the basis of the difference between the setpoint and the value
read on the delivery manifold of the secondary system.
In the same way that modulation is based on the system sensor,
the following parameters intervene:
169 defines the maximum setpoint decrease
170 defines the maximum setpoint increase