Boiler Water Temperature Control - Viessmann VITOTRONIC 100 GC1B Installation And Service Instructions Manual

Vitotronic 100, GC1B Installation and Service

Boiler Water Temperature Control

Brief Description
The boiler water temperature is regulated by starting
and stopping the burner or through modulation.
The set boiler water temperature is determined from
the following parameters:
– Set supply temperature of the heating circuit A1
(system circuit) or the heating circuits connected
via the LON
– External demand
– Set DHW temperature
The set boiler water temperature is subject to the boiler
and the heating/control versions.
The boiler coding card defaults a minimum boiler water
temperature that must be maintained to protect the
boiler.
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.
For heating the DHW tank, a set boiler water
temperature is defaulted that lies 20 K above the
set DHW temperature (change in coding address
"60" in category 3 "DHW").
Functions
The boiler water temperature is captured by the following
equipment:
Fixed high limit STB (liquid expansion)
Adjustable high limit TR (liquid expansion)
Boiler water temperature sensor (change in resistance)
Upper Control Range Limits
Fixed high limit STB 230/210ºF (110/99ºC)
Adjustable high limit TR 203/189ºF (95/87ºC)
Electronic maximum temperature limit:
– Setting range: 68/260ºF (20 to 127ºC)
– Changed via coding address "06" in the "Boiler"
category. Lower control range limits
Lower Control Range Limits
In standard mode and when frost protection is enabled,
the boiler water temperature will be regulated subject to
the respective boiler
Boiler Protection Function
Therm-Control
(Start-up system)
For heating systems with distributor installed close
to the boiler.
Requirement:
The boiler water flow rate in the startup phase
(e.g. after a weekend shutdown) must be able
to be reduced by at least 50%.
Also affects the heating circuits.
Function
Single Boiler Systems
The Therm-Control sensor, installed near the return
connector, captures the return temperature.
The burner is ramped up to full load if the factory-
selected set temperature (defaulted by the boiler coding
card) is not being achieved. The flow rate is reduced
via the mixing valve.
When the set temperature is exceeded, the mixing
valves are opened and the flow rate gradually increased
to 100%.
Multi Boiler Systems
The Therm-Control sensor, installed near the return
connector, captures the return temperature.
The burner is ramped up to full load if the factory-
selected set temperature (defaulted by the boiler coding
card) is not being achieved. The flow rate is reduced
via the isolation valve. Where the Therm-Control sensor
cannot affect the isolation valves it must, instead,
regulate the downstream heating circuits.
When the set temperature is exceeded, the isolation
valve is opened and the flow rate gradually increased
to 100%.
Function Description
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