Viessmann VITODENS 242-F Installation And Service Instructions Manual page 152

Function description
Control unit
(cont.)
The primary store is heated up to the set
DHW temperature. Heating stops when
the specified temperature has been
reached at the cylinder temperature sen-
sor.
Reheating when DHW is drawn off
When DHW is drawn off, cold water
enters at the bottom of the primary
store.
The heating circuit pump is switched ON
and the 3-way diverter valve is changed
over, if the cylinder temperature sensor
recognises a temperature lower than the
set value.
■ The cylinder primary pump is switched
ON if the boiler water temperature ≥
set DHW temperature.
■ The burner is switched ON if the boiler
water temperature ≤ set DHW temper-
ature, and the cylinder primary pump
is switched ON when the required
boiler water temperature is reached.
DHW heating via solar collectors
If a temperature differential is measured
between the collector temperature sen-
sor and the cylinder temperature sensor
of the solar control module, which is
greater than the start temperature differ-
ential set in the control unit, the solar cir-
cuit pump is started and the DHW cylin-
der is heated.
152
After heating has ended, the cylinder pri-
mary pump and the 3-way diverter valve
remain on for a further 30 s.
DHW is regulated to the set temperature
via the outlet temperature sensor.
The primary store continues to be heated
up after the draw off process has termi-
nated, until the set DHW temperature
has been reached at the cylinder tem-
perature sensor.
The cylinder primary pump and the 3-
way diverter valve remain on for a further
30 s.
The pump is stopped if the temperature
falls below the stop temperature differ-
ential between the collector temperature
sensor and the cylinder temperature
sensor of the solar control module.
The solar circuit pump is stopped if the
set maximum temperature or the tem-
perature set at the temperature limiter is
reached.