Minimum Water Flow (Heat Exchanger Protection); Heating System Pressure Test - Riello Array AR 3000 Installation And Operation Manual

Adjusting the parameters on that screen, the reset curve below
will modify shape and slope to meet the needs of the specific ap-
plication.
°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. 39 Reset Curve
− The boiler will fire only when there is a call for heat and the
heating temperature setting is higher than the actual sup-
ply temperature. Hold buttons "+" or "-" on the Cascade
screen (Fig. 46) to select the desired heating temperature. If
the external temperature sensor is connected (see Section
"2.13.3 Outdoor Temperature Sensor" pag. 15), check that
the calculated temperature is higher than the actual boil-
er 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 Man-
agement 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 (Figure
35). To enable this operation mode, the parameter CH mode
must be set to 4 (see Array Control System Manual for ac-
cessing the parameter list).
CH Setpoint
Maximum
CH Setpoint
Minimum
1.0 1.5
ON/OFF
OFF
Hysterese
Fig. 40 10VDC Control mode
The CH setpoint Min and CH setpoint Max parameters can be ad-
justed to provide the desired temperature adjustment band. A
heat request will be generated by an input of 1.5 volts or higher.
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
2.0
Voltage
ON
The setpoint modulation will occur between 2 and 9 volts. The re-
quest 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.
3.5.1 Minimum
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, the burner automat-
ically shuts off.

3.5.2 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. 41.
The error will disappear when the pressure is back at the right
value. To prevent accidental relief valve openings, fill the heating
circuit slowly.
10
Fig. 41 Temperature/Pressure Gauge location
23
COMMISSIONING
Water Flow (Heat
Temperature/Pressure
Gauge
Exchanger