Viessmann Vitotwin 300-W Installation And Service Instructions For Contractors page 154

Function description
Boiler temperature control
Start optimisation
To ensure that sufficient heat is available
at the start of operation with standard
room temperature, the Stirling burner
can start up to 4 h beforehand (delivered
condition). The actual start time is calcu-
lated and optimised by the control unit
via an adaptive function. The earliest
possible start time can be selected in
codes 789, 1089 and 1389.
Stop optimisation
The control unit calculates the earliest
possible stop time for the burners by
means of an adaptive energy optimisa-
tion function.
Power demand function
The buffer temperature sensor B42
should be connected for the power
demand function (code 5935 in the deliv-
ered condition to "Buffer sensor
B42").
The power demand function will only be
activated if the heating water buffer cyl-
inder or DHW cylinder are still able to
accept heat.
The Stirling burner is switched on once
until buffer temperature sensor B41 rea-
ches the set temperature of 60 °C or the
time for forced cylinder charging expires
(code 6282, delivered condition is 2 h).
154
(cont.)
The start time for the auxiliary burner can
be selected in codes 790, 1090 and 1390
(delivered condition 0 min).
The burner can start 1 h earlier for DHW
heating (delivered condition). The earli-
est possible start time can be selected in
code 5011.
The stop time for the burners can be
selected in codes 791, 1091 and 1391
(delivered condition 60 min).
Note
If buffer temperature sensor B42 is not
connected, the power demand function
is still possible subject to limitations.
There is no reserved storage volume for
the power demand function in the heat-
ing water buffer cylinder or the DHW cyl-
inder. The Stirling engine runs until the
set cylinder temperature of 60 °C is
reached at B41.
Activation options
■ Power demand function key
remote control unit
■ Time program 5
■ External demand:
Connect to input EX1 or EX2 on the
230 V∼ extension and select "Ext heat
dem, rel Eng bu" in the correspond-
ing codes 5980 or 5982.
on the