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Building Technologies Boiler sequence controller RMK770 CE1P3132en
HVAC Products 7 Boiler control 23.04.2009
7.9.1 Maximum limitation of the boiler temperature
This setting provides maximum limitation of the boiler temperature setpoint. For burner
control, this value represents the switch-off point. In this range, the boiler’s switching
differential is calculated downward.
Maximum limitation of the boiler temperature is always active. The only exception is the
wiring test.
20 10 0 -10 -20
40
30
60
50
80
70
TBo
TBoMax
TBoMin
TBoSp
SDBo
3131D39
HD
°C
0
HD Heat demand
SDB0 Boiler switching differential
Tbo Boiler temperature
TboMax Maximum limit of the boiler temperature
TboMin Minimum limit of the boiler temperature
TboSP Boiler temperature setpoint
7.9.2 Minimum limitation of the boiler temperature
This setting provides minimum limitation of the boiler temperature setpoint. For burner
control, this value represents the switch-on point. In this range, the boiler’s switching
differential is calculated upward.
The point in time the minimum boiler temperature is maintained depends on the boiler
shutdown setting (see below).
When there is a heat request, the minimum boiler temperature is always active.
If a minimum return temperature is required, it must be ensured that the minimum boiler
temperature is set to a level which lies a few Kelvin above the minimum return tempera-
ture.
7.9.3 Protective boiler startup
To protect the boiler against condensation, a minimum boiler temperature is usually
preset. This ensures that, in normal operation, the boiler temperature does not fall
below a minimum level.
Main menu > Commissioning > Settings > … or
Main menu > Settings > Boiler … > Limitations
Operating line Range Factory setting
Protective boiler startup On / Off On
To prevent the boiler temperature from staying below the minimum temperature for
unnecessary lengths of time, the amount of heat drawn by DHW heating and the heat-
ing circuits can be restricted until the boiler temperature has again risen above the
minimum limit value. Therefore protective boiler startup generates critical locking
signals but only for the lead boiler (for more detailed information, refer to section 5.6
“Heat demand and load control”).
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