Viessmann VITOTRONIC 100 Installation And Service Instructions Manual page 90

Installation
Connecting an AC burner
A
90
BN
BK
BU
B
A To control unit
B To burner
90
(cont.)
Terminal codes
T6, T8 Control chain
Burner stage 2 ON
or
Modulation controller open
T6, T7 Control chain
Burner stage 2 OFF
or
Modulation controller closed
B
Signal pass direction:
Control unit → burner
Y
Signal pass direction:
Burner → control unit
Colour coding to DIN IEC 60 757
BK black
BN brown
BU blue