Siemens Building Technologies
Basic Documentation RVL470
CE1P2522E / 30.03.2000
Landis & Staefa Division
Function block "Boiler"
31/68
10. Function block "Boiler"
Function block "Boiler" acts as a two-position controller and is used for direct burner
control. Depending on the type of plant, it acts as a
•
boiler temperature controller for weather-compensated control of a space heating
system (plant type 2)
•
boiler temperature controller for demand-compensated control of a main flow (plant
type 5)
10.1. Operating lines
Line
Function, parameter
Unit
Factory
setting
Range
91
Operating mode of boiler
0
0 / 1
92
Maximum limitation of boiler temperature
°C
95
25...140
93
Minimum limitation of boiler temperature
°C
10
5...140
94
Switching differential
°C
6
1...20
95
Minimum 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 second burner stage
min
20
0...40
99
Operating mode pump M1
1
0 / 1
10.2. Operating mode
When there is no demand for heat (e.g. due to the ECO function), three different boiler
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:
Boiler operating mode
Controller's operat-
ing mode
With manual shutdown
With automatic shutdown
Stand-by
Boiler OFF
Boiler OFF
AUTO
Boiler at min. limit value
Boiler OFF
REDUCED
Boiler at min. limit value
Boiler OFF
NORMAL
Boiler at min. limit value
Boiler OFF
With plant type 5, it is not possible to select all operating modes (refer to section "3.4.
Operating modes").
When there is demand for heat, the boiler always supplies heat, which means that the
boiler's operating mode will always be ON.
10.3. Limitations
10.3.1. 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 boiler temperature is limited, the display shows:
= for maximum limitation
= for minimum limitation
These limitations cannot be used as safety functions. For that purpose, thermostats,
thermal reset limit thermostats, etc., must be used.