Viessmann Vitoligno 300-P Service Instructions For Contractors page 109

Control functions
Priority control
■ With priority control: (Code "A2:2"):
The set flow temperature will be adjus-
ted to 0 °C whilst the cylinder is being
heated up.
The mixer closes and the heating cir-
cuit pump is switched OFF.
■ Without priority control:
The heating circuit control unit contin-
ues to operate with the same set
value.
■ With modulating priority control in con-
junction with heating circuits 1 and 2:
The heating circuit pump remains
switched ON. The set flow tempera-
ture of the heating circuits will be
reduced, for as long as the set boiler
water temperature has not been
reached during cylinder heating.
The set flow temperature is deter-
mined from the following parameters:
– Outside temp.
– Differential between the set and the
actual boiler water temperature
– Heating curve slope and level
– Setting of coding address "A2"
Frost protection
The DHW cylinder will be heated to
20 ºC if the DHW temperature falls below
5 ºC.
Auxiliary function for DHW heating
This function is activated by providing a
second set DHW temperature via coding
address "58" and activating the fourth
DHW phase for DHW heating.
(cont.)
Set DHW temperature
The set DHW temperature can be adjus-
ted between 10 and 60 ºC.
The set range can be extended via cod-
ing address "56".
DHW circulation pump
The DHW circulation pump delivers hot
water to the draw-off points at adjustable
times.
Up to four time phases can be set at the
time switch.
Auxiliary circuits
DHW heating in conjunction with the
heating circuits can be disabled or ena-
bled by changing over the heating pro-
gram (see coding address "D5").
System with Vitosolic
A third set DHW temperature can be
defaulted via coding address "67".
Reheating by the boiler will be sup-
pressed above this value. The DHW cyl-
inder is heated exclusively by the solar
thermal system.
Function description
109