Strebel S-CB Px 120, Installation Operating & Maintenance Manual

Page: 72 / 118

S-CB Px 120 Manual 72
11.2. Heating
The following chapters describe the different functions of the boiler and their related “controlling behaviour set-
tings” as a central heating boiler.
11.2.1. C
ONTROLLING BEHAVIOUR SETTINGS
The factory settings for all heating applications are working fine and it is therefore advised not to change these
settings. If changes are needed always consult the manufacturer for advice.
P5 AO Blocking offset flow temperature control (display A2).
The amount of degrees the measured temperature exceeds the active flow temperature set point before the heat
demand stops. Only active when the unit is controlled by the internal flow sensor (S1) and used for single unit
control.
P5 AL Hysteresis CH Flow temperature control (display A4).
The amount of degrees that the measured temperature must drop, relative to the active flow temperature set point
+ Offset (Parameter
P5 AO ), before the heat demand starts. This function is active when the unit is controlled by
the internal flow sensor (S1) and used for single units. When controlling cascaded units with an external system
sensor (S3), this sensor will be used.
P5 AP Proportional range single heating boiler (display A3).
The proportional range for controlling the flow temperature of the boiler. This function is active when the unit is
controlled by the internal flow sensor (S1) and used for single units. When controlling cascaded units with an ex-
ternal system sensor (S3), this sensor will be used.
P2 MI Blocking offset System CH temperature control (display A6).
The amount of degrees the measured temperature exceeds the active flow temperature set point before heat
demand stops. Only active when the unit is controlled by an external system sensor (S3).
The following graph shows the relation between the several parameters.
WHEN CONTROLLING ON INTERNAL
FLOW SENSOR
Settings:
P5 AO Offset = 5°C
P5 AP Proportional band = 15°C
P5 AL Hysteresis = 10°C
Temp. set point = 50°C
Burner starts at 45°C
Set point + Offset - Hysteresis = 50+5-10=
45°C
Burner stops at 55°C
Set point + Offset = 50 + 5 = 55°C
WHEN CONTROLLING ON EXTERNAL
FLOW SENSOR
Settings:
P2 MI Offset = 5°C
P5 AP Proportional band = 15°C
P5 AL Hysteresis = 10°C
Temp. set point = 70°C
Burner starts at 65°C
Set point + Offset - Hysteresis = 70+5-10=
65°C
Burner stops at 75°C
Set point + Offset = 70 + 5 = 75°C
BOILER OFF
SETPOINT
ALLOWED TO
MODULATE
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BOILER ON
SETPOINT + OFFSET