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Siemens Building Technologies Basic Documentation RVL471 CE1P2524E
HVAC Products 12 Function block "Boiler" 23.10.2002
12 Function block "Boiler"
Function block "Boiler" acts as a 2-position controller and is used for direct burner con-
trol. Depending on the type of plant, it acts as a:
• boiler temperature controller for weather-compensated control of a space heating sys-
tem (plant type 2–x)
• boiler temperature controller for demand-compensated control of a main flow (plant
type 5–x)
12.1 Operating lines
Line Function, parameter Unit Factory
setting
Range
91 Operating mode of the boiler 0 0 / 1
92 Maximum limitation of the boiler temperature °C 95 25...140
93 Minimum limitation of the boiler temperature °C 10 5...140
94 Switching differential of the boiler °C 6 1...20
95 Minimum limitation of the burner running time min 4 0...10
96 Release limit for second burner stage °C*min 50 0...500
97 Reset limit for second burner stage °C*min 10 0...500
98 Waiting time for second burner stage min 20 0...40
99 Operating mode pump M1 1 0 / 1
12.2 Operating mode
The boiler’s operating mode for situations when there is no demand for heat (e.g. due
to the ECO function),can be selected: 3 operating modes are available:
• With manual shutdown: The boiler will be shut down when there is no demand for heat
and operating mode standby
is selected (setting 0 on operating line 91)
• With automatic shutdown: The boiler will be shut down when there is no demand for
heat, irrespective of the selected operating mode (setting 1 on operating line 91)
Boiler operating modes, when there is no demand for heat:
Controller's operat-
ing mode
Boiler operating mode
With manual shutdown With automatic shutdown
Standby Boiler OFF Boiler OFF
AUTO Boiler at minimum limit value Boiler OFF
REDUCED Boiler at minimum limit value Boiler OFF
NORMAL Boiler at minimum limit value Boiler OFF
With plant types 5–x, it is not possible to select all operating modes (refer to section
“3.7 Plant type and operating mode").
When there is demand for heat, the boiler always supplies heat, which means that the
boiler's operating mode in that case is always ON.
12.3 Limitations
12.3.1 Maximum limitation of the boiler temperature
For maximum limitation of the boiler temperature, the maximum limit value can be ad-
justed. The switch-off point cannot exceed the maximum limit value. The switch-on
point will then be lower by the amount of the set switching differential.
If the return temperature is limited, the display shows
.
This maximum limitation cannot be used as a safety function; for that purpose, thermo-
stats, thermal reset limit thermostats, etc., must be used.
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