Viessmann Vitotwin 300-W Installation And Service Instructions For Contractors page 157

Cylinder temperature control
In "Locking time min supp bu" (codes
3201) it is possible to select how long the
Stirling burner is permitted to operate
after start-up in order to reach the set
boiler water temperature without the
auxiliary burner starting during this time.
The output of the auxiliary burner is limi-
ted to the minimum output for the "Rel
time min mod supp bu" (code 3208). A
new time-temperature integral is calcu-
lated after the auxiliary burner starts. The
auxiliary burner starts to modulate when
this reaches the value "Rel integr mod
supp bu" (code 3209). These three
codes relate to heating water heating.
DHW heating is excluded from this rule.
The preset values are designed to meet
the requirements of detached and two-
family houses.
The following codes influence cylinder temperature control:
1620, 1630, 1640, 1641, 1642.
Time programs
For DHW heating, up to 3 changes per
day between standard and reduced
DHW temperature can be programmed
(3 time phases).
At the factory, time phase 1 is set for
every weekday from 06:00 to 22:00 h.
This means that during that time, DHW
is heated to the selected temperature.
Set DHW temperature
The set DHW temperature can be adjus-
ted between 8 and 68 °C.
Set DHW temperature in standard mode:
Code 1610.
(cont.)
The inertia with which the auxiliary
burner starts for DHW heating can be
amended with code 3203: The lower the
value, the slower it starts.
At the end of DHW heating, it is possible
to choose between absolute mode and
modulating mode (delivered condition).
In modulating mode, at the end of DHW
heating, the excess energy is used for
central heating (only relevant when
using a multi mode heating water buffer
cylinder). The mode can be selected with
code 1630.
For a description, see codes overview.
To ensure that there is enough hot water
after 06:00 h, the burners can start ½ to
4 h earlier (code 5011, delivered condi-
tion 1 h).
Set DHW temperature in reduced mode:
Code 1612.
Function description
157