
118/232
Building Technologies
Boiler Sequence Controller RMK770
CE1P3132en
HVAC Products
7 Boiler control
23.04.2009
In case of plants with mixing valve for the maintained boiler return temperature, the
protective boiler startup function is provided by the mixing valve. In that case, no lock-
ing signals for the protective boiler startup is generated.
It can be selected whether or not the boiler pump shall be switched off when protective
boiler startup is active (pump off).
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Boiler … > Limitations
Operating line
Range
Factory setting
Protective boiler startup
Pump on / Pump off
Pump on
Protective boiler startup can be interrupted by the controller in order to ensure frost
protection for the plant in the event the burner initiates lockout, for example.
In the case of simultaneous protective boiler startup and frost protection for the plant,
the boiler temperature gradient must turn positive within 15 minutes. Otherwise, the
locking signal will become invalid for at least 15 minutes. After 15 minutes, protective
boiler startup becomes active as soon as the boiler temperature gradient turns positive.
7.9.4
Optimization of the minimum boiler temperature
With setting “Optimization of the minimum boiler temperature = On”), the control selects
the switch-on point such that, in normal situations, the boiler temperature does not drop
below the minimum level. Using this function, a load-dependent forward shift of the
burner’s switch-on point can be achieved. In that case, the minimum boiler temperature
need not be determined with an unnecessarily great safety factor since with large loads,
the burner switches on earlier, and with small loads, later. Hence, the range in which
the boiler temperature can be compensated can be widened.
Based on the boiler temperature gradient, the controller calculates the burner’s switch-
on point to ensure that the boiler temperature does not drop below the minimum level.
When the function is deactivated, the controller switches the burner on at the minimum
boiler temperature TboMin.
TBoMin
31
31
D
40
Burner
swich-on
command
TBoMin
31
31
D
41
Burner
swich-on
command
Optimization of minimum boiler
temperature on
Optimization of minimum boiler
temperature off
7.9.5 Boiler
shutdown
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Boiler … > Operation settings
Operating line
Range
Factory setting
Boiler shutdown
Without / Automatic / Sum-
mer
Automatic
Here, it is possible to select at what point in time minimum limitation of the boiler tem-
perature shall become active.
Boiler pump
Protective boiler startup
and frost protection for
the plant