143
B
A
1 2 3
A
Blocking the boiler externally
(floating contact for switching LV)
B
Start the boiler externally as the last one in the boiler sequence
(floating contact for switching LV)
Con-
tact
Closed
Open
A
– The boiler is blocked and
has been removed from
the boiler sequence.
– Butterfly valve is closed
and the boiler circuit
pump stops.
– The other boilers provide
the required heating.
The boiler is integrated into
the current boiler sequence.
B
This boiler is started if the
other boilers in the heating
system cannot provide suf-
ficient heat.
The boiler is integrated into
the current boiler sequence.
External control of the modulating burner
Make connections at plug
aVH
and
aBÖ
.
Note
The contact at terminals 2 and 3 of plug
aVH
is always required to
prevent boiler damage.
This contact must always be closed on the lead boiler.
STB
ON
TR
ON
TR
N
STB
B
G
D
E
41
B4
L
S3
N
T1
T2
41
L
B4
S3
T2
T1
N
F
146
A
12
3
T6 T7 T8
90
C
A
/
B
Boiler enable from on-site modulation controller (butterfly
valve open)
A
Floating contact for switching LV
B
Floating contact for switching 230 V~
C
Burner base load
(floating contact for switching 230 V~)
D
T6, T7: Reduce burner output (modulation controller closed)
(floating contact for switching 230 V~)
E
T6, T8: Increase burner output (modulation controller open)
(floating contact for switching 230 V~)
F
Plug to the burner
G
Plug to the control unit
Note
If the boiler is enabled via a contactor, the conditions of safety category
II and the operation of safety LV (SELV) must be ensured.
Contact Closed
Open
A
/
B
Boiler enabled. The butter-
fly valve opens.
The butterfly valve is closed
after approx. 5 s. External
burner start not possible.
C
Burner on (base load). An
on-site modulation control-
ler regulates the load-de-
pendent modulation. The
boiler water temperature is
restricted by the electronic
maximum temperature lim-
iter.
Burner off.
Hook-up of on-site control units via LON
The Vitotronic control units are equipped with an open standard LON
interface. With standard LONWORKS network variables (SNVT).
This universal, decentralised network for automated building control
systems not only allows communication between Vitotronic control
units, but also the hook-up of on-site systems and devices from various
manufacturers.
It enables, for example, individual room control units or building man-
agement systems to be directly connected to Vitotronic control units.
Further information can be found in the LON manual; see
www.viessmann.de\lon.
Control units
(cont.)
94
VIESMANN
Gas condensing boilers
9
5822 449 GB