Viessmann VITOLIGNO 300-C Installation And Service Instructions Manual page 14

Boiler Connections
Vitoligno 300-C Installation/Service
System Layout 1
Applications
DHW heating by solar thermal system and pellet boiler,
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 5 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/zP/uP 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/zP/uP
is taken from heating water buffer tank eP via heating
circuit pumps rQ/tQ/zQ/uQ. The respective supply
temperatures are controlled to their set value in weather-
compensated mode via 3-way mixing valves rE/tE/zE/uE.
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/zP/uP is controlled by incremental
opening and closing of mixing valves rE/tE/zE/uE.
DHW heating by solid fuel boiler
If 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.
Heating the dual mode DHW tank with solar energy
If the temperature differential between collector
temperature sensor wT and return temperature sensor
wZ (bottom tank temperature sensor) exceeds the set
start temperature differential, speed-controlled solar
circuit pump wE is started and the dual mode DHW tank
is heated up. If the temperature differentials reach their
shutdown thresholds, the solar circuit pump is switched
off accordingly. When the set temperature selected at
the solar control unit is reached at bottom reference
temperature sensor wZ, solar heating of the dual mode
DHW tank is stopped.
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