Function Description; Boiler Temperature Control - Viessmann Vitotwin 300-W Installation And Service Instructions For Contractors

Boiler temperature control

A set value for the boiler water tempera-
ture is established by the control unit as
a function of the following parameters:
■ Outside temperature
■ Heating curve
■ Set DHW temperature.
The determined set boiler water temper-
ature is transferred to the burner control
unit. From the set and actual boiler water
temperatures, the burner control unit cal-
culates the modulation level and regu-
lates the burners accordingly.
Burner sequence
Initially the Stirling burner starts when a
heat demand is issued. If the set boiler
water temperature is not reached or if the
temperature drops further, the auxiliary
burner starts after a delay. If the Stirling
burner has developed a fault, the auxili-
ary burner starts immediately.
B4
A
B
C
D
E
F
B41/B42
A Temperature, heating water buffer
cylinder
B Stirling burner off
C Auxiliary burner off
D Stirling burner on

Function description

The boiler water temperature is limited
by the electronic temperature controller
(85 °C, can be adjusted in code 2212)
and temperature limiter (100 °C).
E Set heating flow temperature
F Auxiliary burner on
TB Differential temperature (delivered
condition 8 K)
Codes 830, 1130 and 1430
153