Weather-Compensated Control Unit - Viessmann VITODENs 200 Installation Instructions Manual

Function description

Weather-compensated control unit

Heating mode
The control unit determines a set boi-
ler water temperature subject to out-
side temperature or room temperature
(if a room temperature dependent
remote control is connected) and the
slope/level of the heating curve. The
determined set boiler water tempera-
ture is then transferred to the burner
control unit. From the set and actual
boiler water temperatures, the burner
control unit calculates the modulation
level and controls the burner accord-
ingly. The burner control unit limits the
boiler water temperature: Through the
control thermostat to 74 °C, and
through the electronic temperature
limiter to 82 °C. The temperature lim-
iter in the safety chain locks out the
burner control unit at a boiler water
temperature of 100 °C.
DHW loading with gas fired combi-
nation boilers
If the flow switch recognises that
DHW is drawn off (> 3 l), the burner
and circulation pump are switched
ON, and the three-way valve changes
over to DHW loading. The burner
modulates to reach the DHW outlet
temperature and is limited on the boi-
ler side by the temperature limiter
(82 ºC). With activated comfort opera-
tion, the plate heat exchanger will be
held to a standby temperature of
"42 °C ON" and "46 °C OFF".
98
DHW loading with a gas fired boiler
The DHW heating will be activated if
the cylinder temperature falls 2.5 K
below the set cylinder temperature.
The burner and the cylinder loading
pump are switched ON. In the deliv-
ered condition, the set boiler water
temperature lies 20 K higher than the
set cylinder temperature. If the actual
cylinder temperature rises 2.5 K
above the set cylinder temperature,
the burner will be switched OFF and
the cylinder loading pump run-on time
will be activated.
Supplementary DHW heating
The backup heating function is acti-
vated if a switching period is selected
for the fourth time phase. This period
must lie outside the switching times
for standard DHW heating to enable
the control unit to recognise the sig-
nal. The set temperature value for
backup heating is adjustable in coding
address 58.