Viessmann VITOLIGNO 300-P Service Instructions Manual page 27

Further details regarding the individual steps
The heating circuit pump is switched on
via the heating circuit pump logic, provi-
ded there is a heat demand. Upon
demand, the boiler is operated with the
required set boiler water temperature or
the minimum boiler water temperature of
60 °C.
The boiler shuts down if neither the DHW
cylinder nor the heating circuits issue
any more demands.
Control of a solar thermal system
The Vitosolic 200 (type SD4) wZ regu-
lates the DHW heating and central heat-
ing backup using solar energy.
DHW heating by the solar thermal
system
If the temperature differential between
collector temperature sensor wQ and cyl-
inder temperature sensor qT exceeds
the temperature differential ΔT
circuit pump wE starts. Pump wE is stop-
ped if:
■ The actual temperature falls below the
temperature differential ΔT
■ The electronic temperature limit (max.
95 °C) at the control unit or that selec-
ted at the high limit safety cut-out (if
required) is exceeded.
Commissioning, inspection, maintenance
Central heating/central heating
backup by the solar thermal system
If the DHW cylinder cannot be heated
and the temperature differential between
collector temperature sensor wQ and
buffer cylinder temperature sensor tE
exceeds temperature differential ΔT2
circulation pump wO starts to heat the
heat exchanger. The pump will be stop-
ped if the actual temperature falls below
the temperature differential ΔT2
reaches the maximum buffer cylinder
temperature T
inside the heating water buffer cylinder
will be electronically limited by the high
limit safety cut-out (if required). This
device stops circulation pump wO if the
set temperature is exceeded. The run-
time of circulation pump wO is interrupted
for approx. 2 min roughly every 15 min
(times are adjustable), to check that the
temperature at the collector temperature
, solar
ON
sensor is high enough to change over to
DHW cylinder heating. The DHW cylin-
der will continue to be heated if, during
that time, value ΔT-col is exceeded.
OFF
(cont.)
. The temperature
cyl2max
,
ON
or
OFF
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