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• After the Date & Time setting, if an outdoor probe is connected, the
Reset Curve screen must be accessed (through the Settings screen)
to set the curve parameters:
Fig. 45 Reset Curve screen
Adjusting the parameters on that screen, the reset curve below will
modify shape and slope to meet the needs of the specific application.
°C °F
93
200
Reset Curve
82
180
Design Boiler
71 160
60
140
49
120
38
100
Reset Cuve
27
80
Boiler Mild
Weather
16
60
°F
20
°C
-6
Reset Curve Outdoor Design
Fig. 46 Reset Curve
• The boiler will fire only when there is a call for heat and the heating
temperature setting is higher than the actual supply temperature. Hold
buttons "+" or "-" on the Cascade screen (Fig. 53) to select the desired
heating temperature. If the external temperature sensor is connected
(see Section "4.5.2 Outdoor Temperature Sensor" pag. 21), check
that the calculated temperature is higher than the actual boiler
temperature and that the outdoor temperature is lower than "warm
weather shut down" temperature.
• The boiler CH setpoint can be controlled by an analog input signal
provided by a remote means such as a Building Management
System or a system controller. The analog input 0-10 VDC, is used
to adjust the boiler setpoint between the CH_Setpoint_Min and the
CH_Setpoint_Max settings (Fig. 47). To enable this operation mode,
the parameter CH mode must be set to 4 (see SSB Control System
Manual for accessing the parameter list).
NOTE: to enable CH mode 4, terminals 9 and 10 (Enable/Disable) on
Low voltage strip must be jumpered.
SSB
Reset Curve Boiler Maximum
Reset Curve Boiler Minimum
OUTDOOR TEMP. (°C/ )
°F
40
60
80
100
4
16
27
38
1)Reset Curve Outdoor Mild Weather
2) Warm Weather Shutdown
CH Setpoint
Maximum
CH Setpoint
Minimum
1.0
1.5
ON/OFF
OFF
Hysterese
Fig. 47
10VDC Control mode
The CH setpoint Min and CH setpoint Max parameters can be adjusted to
provide the desired temperature adjustment band. A heat request will be
generated by an input of 1.5 volts or higher. The setpoint modulation will
occur between 2 and 9 volts. The request for heat will be removed when
the voltage drops below 1 volt.
All other safety and control functions associated with the boiler will react
normally to adverse condition and override control of the analog signal to
prevent an upset condition.
5 .5 .1
Minimum Water Flow (Heat Exchanger Protection)
This unit is self-protected against low water flow. A flow meter
continuously monitors the water flow to each module. If the water flow
decreases below the minimum stated (default threshold: 50l/min =
13.2GPM), the burner automatically shuts off.
5 .5 .2
Heating System Pressure Test
If the pressure inside the heating circuit falls below the minimum pressure
for the system (7.5 PSI), the appliance switches off and the 905PB inner
display shows "Low water pressure" to indicate that it is necessary to
restore the correct pressure.
Open the filling valve and check the pressure on the temperature/
pressure gauge of Fig. 48.
The error will disappear when the pressure is back at the right value. To
prevent accidental relief valve openings, fill the heating circuit slowly.
Temperature/Pressure Gauge
Fig. 48 Temperature/Pressure Gauge location
Commissioning | 33
2.0
Voltage
ON
6720866942 (2018/06) US
10
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