Viessmann VITOLIGNO 300-C Installation And Service Instructions Manual page 130

Function Description
Control Functions
Tank temperature control
Brief description
Tank temperature control is a constant temperature

control. It operates by starting and stopping the
circulation pump for tank heating.
Central heating is switched off during tank heating.

When tank priority control is active, see coding
address A2, heating group.
Coding addresses that influence the tank

temperature 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
circulation 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.
All tank heating sequences will be completed irrespective
of the time program.
Priority control
The priority control of the tank heating can be adjusted
individually for each heating circuit.
With priority control: (coding address 2 "A2:2",

heating group):
The set supply temperature will be adjusted to 32°F
(0°C) during tank heating.
The mixing valve closes and the heating circuit pump
is switched off.
With priority control: (coding address 2 "A2:1",

heating group):
The set supply temperature will be adjusted to 32°F
(0°C) during tank heating.
The mixing valve closes and the heating circuit pump
is running. 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 reduced priority control: (coding address 2

"A2:3", heating group)
The heating circuit pump remains switched on. During
tank heating, the set supply temperature of the heating
circuit will be reduced to the set value of reduced
heating mode until the set supply temperature has been
reached.
The set supply temperature is determined from the
following parameters:
– Outdoor temperature
– Differential between the set and the actual boiler
water temperature
– Heating curve slope and shift
Without priority control: (coding address "A2:0",

heating group)
The heating circuit control unit continues to operate
with the same set value.
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(continued)
Vitoligno 300-C Installation/Service
Set DHW temperature
The set DHW temperature can be adjusted between
50°F and 158°F (10°C and 70°C).
The set range can be extended via the menu.
DHW recirculation 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.
System with Vitosolic
A second set DHW temperature can be specified via
coding address "67".
Reheating by the boiler will be suppressed above this
value. The DHW tank is heated exclusively by the solar
thermal system.
Control sequence
The circulation pump for tank heating starts when the
differential between the buffer tank temperature (top
sensor) and the actual tank temperature exceeds the
setting (coding address "0C").
The circulation pump for tank heating stops when the
boiler water/buffer tank temperature (top sensor) falls
below the actual tank temperature by the differential
comprising the values of coding address "0C".
DHW tank goes cold (set value 10 K):
Pump on:

– Starting the circulation pump for tank heating
subject to boiler water temperature (coding "61:0"):
The circulation pump starts when the boiler water
temperature is higher than the DHW temperature.
The DHW tank is hot:
Pump run-on:

After tank heating, the circulation pump runs on
until one of the following criteria is met when the
boiler is operating:
– The differential between the boiler water and DHW
temperature is too small (coding 0C, DHW group)
– The set DHW temperature is exceeded.