Dhw Tank Temperature Control - Viessmann Vitotronic 300 Installation And Service Instructions Manual

Vitotronic 300, GW5B Installation and Service

DHW Tank Temperature Control

Brief description
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.
When the DHW tank is heated, the default set
boiler water temperature is 20 K above 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 circulation 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
circulation 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
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
circulation pump have the same effect on all
heating circuits.
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
circulation pump can be adjusted individually for
each heating circuit.
Priority control
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.
Without priority control: The heating circuit control
unit continues to operate with the same set value.
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
Frost protection
The DHW 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°F and 140°F (10 and 60°C). The set value range can
be extended up to 203°F (95°C) 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 assigned 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
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.
Function Description
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