Viessmann VITOTRONIC300 Installation And Service Instructions Manual page 86

Function Description
DHW Tank Temperature Control
Frost protection
The DHW tank will be heated to 68°F (20°C) if the DHW
temperature sinks below 41°F (5ºC).
Auxiliary function for DHW heating
This function is activated by providing a second set DHW
temperature via coding address "58" in group "DHW"
and activating the fourth DHW phase for DHW heating.
Set DHW temperature
The set DHW temperature can be adjusted between
50 and 140°F (10 and 60°C).
The set value range can be extended to 203°F (95ºC)
via coding address "56" in the "DHW" group.
The set default value of the programming unit and/or
the Vitotrol 300A remote control units can be allocated
via coding address "66" in the "DHW" group.
DHW circulation pump
This delivers hot water to the draw-off points at
adjustable times.
Four time phases can be selected at the control unit
for every day.
Auxiliary circuits
DHW heating in conjunction with the heating circuits
can be disabled or enabled by changing over the heating
program (see coding address "d5" in the "Heating circuit
..." group).
System with primary store system
The above functions also apply in conjunction with
primary store systems.
Set the following codes:
"55:3" in the "DHW" group; "4C:1", "4E:
2" in the "General" group.
System with solar control unit
A third set DHW temperature can be specified via coding
address "67" in the "DHW" group.
The DHW tank is only reheated by the boiler if the
temperature falls below this value.
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Vitotronic 300, GW2B Installation and Service
(continued)
Control sequence
Code "55:0" in the "DHW" group, DHW tank heating
The DHW tank goes cold (set value −2.5 K, adjustable
via coding address "59"):
H The set boiler water temperature is set 20 K higher than
the set DHW temperature (adjustable via coding address
"60").
H Pump on:
– Starting the circulation pump for DHW tank heating
subject to the boiler water temperature (code "61:0").
The circulation pump starts when the boiler water
temperature is 7 K higher than the DHW temperature.
– Immediate start of the circulation pump for DHW tank
heating (code "61:1").
The DHW tank is hot (set value +2.5 K):
H The set boiler water temperature is returned
to the weather-compensated set value.
H Pump run-on:
The DHW tank primary pump runs on after DHW tank
heating until the following criteria are met:
– The difference between the boiler water temperature
and the DHW temperature is less than 7 K.
– The weather-compensated set boiler water
temperature has been reached.
– The set DHW temperature is exceeded by 5 K.
– The set max. run-on time has been reached (coding
address "62").
H Without pump run-on (code "62:0").