Viessmann VITOLIGNO 300-C Installation And Service Instructions Manual page 180

Function description
Control functions
(cont.)
Cylinder temperature control
Cylinder temperature control is a constant tempera-
■
ture control. It operates by starting and stopping the
circulation pump for cylinder heating.
The switching differential is 10 K.
■ During cylinder heating, central heating is switched
off (when cylinder priority control is active see code
A2, Heating group).
Coding addresses that influence the cylinder tem-
■
perature control:
– 0C, 0D (DHW group)
– A2 (Heating group)
For a description, see codes overview
Functions
Time program
An automatic program or an individual time program
may be selected for DHW heating and the DHW circu-
lation pump.
In the individual time program, up to 4 time phases per
day can be set via the time switch for DHW heating,
and 4 time phases for the DHW circulation pump.
Priority control
The priority control of the cylinder heating can be
adjusted individually for each heating circuit.
■ With priority control: (code 2 "A2:1", Heating group):
The set flow temperature will be adjusted to 0 °C
during cylinder heating.
The mixer closes and the heating circuit pump is run-
ning.
Only possible when the heating circuit is wired on the
internal boiler PCB. When using an extension kit for
the heating circuit, the heating circuit pump is
switched off.
■ With priority control: (code 2 "A2:2", Heating group):
The set flow temperature will be adjusted to 0 °C
during cylinder heating.
The mixer closes. The heating circuit pump is
switched off.
■ With reduced priority control: (code 2 "A2:3", heating
group)
The heating circuit pump remains switched on. Dur-
ing cylinder heating, the set flow temperature of the
heating circuit will be reduced to the set value of
reduced heating mode until the set flow temperature
has been reached.
The set flow temperature is determined from the fol-
lowing parameters:
– Outside temperature
Differential between the set and the actual boiler
–
water temperature
Heating curve slope and level
–
■ Without priority control: (code "A2:0", heating group)
The heating circuit control unit continues to operate
with the same set value.
180
Set DHW temperature
The set DHW temperature can be adjusted between
10 and 70 °C.
DHW circulation pump
The DHW circulation pump delivers hot water to the
draw-off points at adjustable times.
Up to 4 time phases can be set at the time switch.
Reheating suppression
A second set DHW temperature can be specified via
coding address "67".
Reheating by the boiler will be suppressed above this
value. The DHW cylinder is heated exclusively by the
solar thermal system.
Control sequence
The circulation pump for cylinder heating starts when
the differential between the buffer cylinder temperature
(top sensor) and the actual cylinder temperature
exceeds the setting (coding address "0C").
The circulation pump for cylinder heating stops when
the boiler water/buffer cylinder temperature (top sen-
sor) falls below the actual cylinder temperature by the
differential comprising the values of coding address
"0C".
DHW cylinder goes cold (set value 10 K):
Pump on:
■
Starting the circulation pump for cylinder heating
–
subject to boiler water temperature (code "61:0"):
The circulation pump starts when the boiler water
temperature is higher than the DHW temperature.
The DHW cylinder is hot:
Pump run-on:
■
After cylinder heating, the circulation pump runs on
until one of the following criteria is met when the
boiler is operating:
– The differential between boiler water and DHW
temperature is too small (code 0C, DHW group).
– The set DHW temperature is exceeded.