Dhw Tank Temperature Control - Viessmann VITOTRONIC300 Installation And Service Instructions Manual

Vitotronic 300, GW2B Installation and Service

DHW Tank Temperature Control

Brief description
H The DHW tank temperature control is a constant
temperature control. This is the result of starting and
stopping the circulation pump for DHW tank heating.
The switching differential is ±2.5 K.
H When the DHW tank is heated, a set supply
temperature is specified that is 20 K higher than the set
DHW temperature (adjustable via coding address "60"
in the "DHW" group).
Functions
Time program
An automatic or an individual time program may be
selected for DHW heating and the DHW recirculation
pump.
Compared with the heating circuit heatup phase,
DHW heating starts 30 min earlier in automatic mode.
The individual time program enables up to 4 time
phases per day to be set for DHW heating and the DHW
recirculation pump for every day of the week.
All DHW tank heating sequences will be completed
independently of the time program.
In conjunction with coding address "7F" in the "General"
group
H Detached house
Code "7F:1":
– Automatic mode
The heating times for heating circuit 1 are applied
to systems with two or three heating circuits.
– Individual time program
The time phases for DHW heating and the DHW
recirculation pump have the same effect on all heating
circuits.
H Apartment building
Code "7F:0":
– Automatic mode
For systems with two or three heating circuits,
the heating times for the relevant heating circuit will
be applied.
– Individual time program
The time phases for DHW heating and the DHW
recirculation pump can be adjusted individually for
each heating circuit.
Priority control
H With priority control: (code "A2:2" in the "Heating
circuit..." group):
The set supply temperature is set to 32°F (0°C) during
DHW tank heating.
The mixing valve closes and the heating circuit pump
is switched off.
H Without priority control:
The heating circuit control unit continues to operate
with the same set value.
H With modulating priority control in conjunction with
heating circuits with mixing valve:
The heating circuit pump remains switched on. The set
supply temperature of the heating circuits will be
reduced, for as long as the set boiler water temperature
has not been reached during DHW tank heating.
The set supply temperature is determined from the
following parameters:
– Outside temperature
– Differential between the set and the actual boiler
water temperature
– Heating curve slope and shift
– Setting of coding address "A2" in the "Heating
circuit..." group
Function Description
85