Viessmann VITOTRONIC300 Installation And Service Instructions Manual page 87

Vitotronic 300, GW2B Installation and Service
DHW Tank Temperature Control
Code "55:1" in the "DHW" group, adaptive DHW tank
heating
With adaptive DHW tank heating, the speed of the
temperature rise during DHW heating is taken into
account.
The DHW tank goes cold (set value −2.5 K, adjustable
via coding address "59"):
H The set boiler water temperature is set 20 K higher
than the set DHW temperature (adjustable via coding
address "60").
H Pump on:
– Starting the circulation pump for DHW tank heating
subject to the boiler water temperature (code "61:0").
The circulation pump starts when the boiler water
temperature is 7 K higher than the DHW temperature.
– Immediate start of the circulation pump for DHW tank
heating (code "61:1").
The DHW tank is hot:
H The control unit checks whether the boiler will
be required to supply heat after the DHW tank
has been heated up or whether residual boiler
heat should be transferred to the DHW tank.
Accordingly, the control unit determines the burner
and circulation pump stop times to prevent the set
DHW temperature being substantially exceeded after
the DHW tank has been heated up.
Code "55:2" in the "DHW" group, DHW tank temperature
control with 2 DHW tank temperature sensors
DHW tank temperature sensor 1 enables the circulation
pump for DHW tank heating and is evaluated for stop
conditions during the pump run-on time.
DHW tank temperature sensor 2:
The DHW tank heating will be switched on early
if a lot of hot water is drawn off. The DHW tank heating
will be switched off early if no hot water is drawn off.
DHW tank goes cold:
H Set value −2.5 K, adjustable via coding address "59"
or
H Actual DHW temperature at sensor 2 < set DHW
temperature x factor for start time (adjustment via
coding address "69")
The DHW tank is hot:
H Set value +2.5 K
and
H Actual DHW temperature at sensor 2 > set DHW
temperature x factor for stop time (adjustment via
coding address "68")
(continued)
Code "55:3" in the "DHW" group, DHW tank temperature
control, primary store system
The DHW tank goes cold (set value −2.5 K, adjustable
via coding address "59"):
H The set boiler water temperature is set 20 K higher
than the set DHW temperature (change via coding
address "60").
H The primary pump in the primary store system starts.
H The 3-way mixing valve opens and then regulates
to the specified set value.
H The circulation pump for DHW tank heating cycles
(briefly switches ON and OFF) until the set supply
temperature has been reached (set DHW temperature
+ 5 K).
Then it runs constantly.
If, during heating, the actual value falls below the
required set temperature, the circulation pump for DHW
tank heating will temporarily cycle again.
The DHW tank is hot:
H DHW tank temperature sensor 1:
Actual value ≥ set value
and
DHW tank temperature sensor 2:
Actual value > set value −1.5 K:
H The set boiler water temperature is returned to the set
weather-compensated value.
H The circulation pump for DHW tank heating stops
immediately when the 3-way mixing valve is fully
opened.
or
H The circulation pump for DHW tank heating stops after
expiry of the run-on time that is selected via code "62".
Function Description
87