Boiler Water Temperature Control - Viessmann VITOTRONIC300 Installation And Service Instructions Manual

Vitotronic 300, GW2B Installation and Service

Boiler Water Temperature Control

Brief description
H The boiler water temperature is regulated by starting
and stopping the burner or through modulation.
H The set boiler water temperature is determined from
the following parameters:
– Set supply temperature of the heating circuits
connected to the control unit and the heating circuits
connected via the LON BUS
– External demand
– Set DHW temperature
H The boiler coding card defaults a minimum boiler
water temperature that must be maintained to protect
the boiler.
H In conjunction with Therm-Control:
The set boiler water temperature will be increased when
the actual temperature at the Therm-Control sensor falls
below the set temperature.
H When the DHW tank is heated up, the default set
boiler water temperature is 20 K above the set DHW
temperature (adjustable via coding address "60"
in the "DHW" group).
Functions
The boiler water temperature is captured by the following
equipment:
H High limit safety cut-out STB (liquid expansion)
H Temperature controller TR (liquid expansion)
H Boiler water temperature sensor NTC 10 kΩ
Upper control range limits
H High limit safety cut-out STB
230/212°F (110/100ºC)
H Temperature controller TR
203/212/230°F (95/100/110ºC)
H Electronic maximum temperature limit:
– Setting range: 68 to 261°F (20 to 127ºC)
– Changed via coding address "06" in the "Boiler"
group.
Lower control range limits
H In standard mode and when frost protection is enabled,
the boiler water temperature will be regulated subject
to the respective boiler.
Function Description
77