Operating instructions

ManualsBrandsViessmann ManualsBoilerWB2B

Fault

code

on the

display

Const. weath.-

comp.

System char-

acteristics

Cause Measures

b5 X X Control mode

as per deliv-

ered condition

Internal fault Replace the con-

trol unit.

b7 X X Burner

blocked

Boiler coding

card miss-

ing, faulty or

incorrect

boiler coding

card

Plug in boiler cod-

ing card or re-

place it, if faulty.

b8 X X Burner

blocked

Flue gas

temperature

sensor lead

broken

Check the flue

gas temperature

sensor (see

page 85).

bA X Mixer M2 reg-

ulates to a

flow tempera-

ture of 20 °C.

Communica-

tion fault –

extension kit

for heating

circuit M2

Check the exten-

sion kit connec-

tions and coding.

Start the exten-

sion kit.

bC X Control mode

without remote

control

Communica-

tion fault –

Vitotrol re-

mote control,

heating cir-

cuit A1

Check connec-

tions, cable, cod-

ing address "A0"

and remote con-

trol DIP switches

(see page 104).

bd X Control mode

without remote

control

Communica-

tion fault,

Vitotrol re-

mote control,

heating cir-

cuit M2

Check connec-

tions, cable, cod-

ing address "A0"

and remote con-

trol DIP switches

(see page 104).

bE X Control mode Vitotrol re-

mote control

incorrectly

programmed

Check remote

control DIP switch

settings (see

page 104).

bF X Control mode Incorrect

LON com-

munication

module

Replace the LON

communication

module.

Fault codes (cont.)

73

Troubleshooting

5692 672 GB