Dhw Tank Temperature Control - Viessmann VITOTRONIC 300 GW2 Installation And Service Instructions Manual

Functional description

DHW tank temperature control

Brief description
The DHW tank temperature control is a
constant value control. It operates on
the basis of switching the circulation
pump for heating the DHW tank on and
off.
The switching differential is ±2.5°C /
4.5°F.
Functions
Time program
An automatic or an individual time
program can be selected for domestic
hot water heating and the DHW
circulation pump.
In the automatic program, domestic
hot water heating precedes the heat-up
phase of the heating circuit by 30
minutes. On systems with several
heating circuits, the time program is
based on the switching times of the
first heating circuit to be heated.
In the individual time program, up to
four switching times per day can be
set on the timer for domestic hot water
heating and the DHW circulation pump.
Once started, heating of the DHW tank
is always completed regardless of the
time program.
The switching times for domestic hot
water heating and the DHW circulation
pump are effective for all heating
circuits. Individual switching times can
be assigned to each heating circuit via
the coding address "7F".
System with DHW tank loading system
The functions described above also
apply in conjunction with DHW tank
loading systems.
Set the following codings:
"4C: 1", "4E: 1", "55: 3".
90
During DHW tank heating, a constant
maximum boiler water temperature is
set and space heating is switched off
(DHW tank priority control optional).
Frost protection function
If the domestic hot water temperature
falls below 10°C / 50°F, the
domestic hot water DHW tank is
heated to 20°C / 68°F.
Additional function for domestic hot
water heating
This function is activated when a
second DHW setpoint value is selected
via coding address "58" and the 4th
activation period for domestic hot
water heating is activated.
Desired domestic hot water
temperature
The desired domestic hot water
temperature can be set in the range
of 10 to 60°C / 50 to 140°F. The
set-point range can be extended to
95°C / 203°F via coding address
"56".
The desired domestic hot water
temperature can be set on the
programming unit of the control unit
and on the Vitotrol 300 remote control
(if installed).
The set-point value can be assigned via
coding address "66".
Coding addresses which influence
the DHW tank temperature control
55, 56, 58 to 62, 64, 66, 70 to 75,
7F, A2.
See page 114 onwards for description.
DHW circulation pump
The DHW circulation pump supplies
hot water to the take-off points at
selectable times. Up to four
switching times can be set on the
timer.
Additional control facilities
The domestic hot water supply can
be blocked and released via
changeover of the heating program.