Viessmann VITOLIGNO 300-C Installation And Service Instructions Manual page 20

Boiler Connections
Vitoligno 300-C Installation/Service
System Layout 2
Applications
DHW heating and central heating by pellet boiler
Heating the heating water buffer tank
The boiler is started when a heat demand is issued to heat
the heating circuits. If the temperature at top boiler start
sensor 1 falls below the set value determined by the
control unit of solid fuel boiler 2, solid fuel boiler 1 starts
up. Boiler circuit pump qZ delivers the heating water to the
heating water buffer tank. Any heat not absorbed by heating
circuits rP/tP is stored in the heating water buffer tank.
Heating of the heating water buffer tank is stopped as soon
as bottom buffer tank temperature sensor 6 exceeds the
set value determined by the solid fuel boiler control unit.
Low temperature protection package
Solid fuel boiler 1 requires a minimum return
temperature. When boiler circuit pump qZ is running, the
valve of return low temperature protection package qU
opens the route from the central heating return to boiler
1 in line with the increasing return temperature and
closes the route from the boiler supply to the boiler return
(bypass).
Heating by heating water buffer tank
The heat required to heat heating circuits rP/tP is taken
from heating water buffer tank eP via heating circuit
pumps rQ/tQ. The respective supply temperatures are
controlled to their set value in weather-compensated
mode via 3-way mixing valves rE/tE.
Heating circuit control with mixing valves
The set supply temperature of every heating circuit is
determined by the following parameters: outdoor
temperature, set room temperature, operating mode and
heating curve. The supply temperature of mixing valve
circuits rP/tP is controlled by incremental opening and
closing of mixing valves rE/tE.
DHW heating by solid fuel boiler
When the set temperature for DHW determined by solid
fuel boiler control unit 2 is undershot at tank temperature
sensor qQ, DHW heating is activated. As soon as the buffer
tank temperature is sufficiently high, DHW circulation pump
for tank heating qW is started. To activate tank priority
control, the mixing valves in the heating circuits can be
closed and the heating circuit pumps switched off.
The type and extent of priority control is adjustable.
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