Viessmann Vitotronic 300 Operating Instructions Manual page 27

Diagnosis and correction
Fault
Heating system does not start up
Burner does not switch on or only
erratically
Burner is operating, but no hot
water
(only on systems with DHW cylin
der)
(continued)
Cause
Heating system switch "8" on the
control unit turned to OFF
Mains electrical isolator switch, if
installed, is switched off
Fuse in the domestic power circuit
or in the control unit has blown or
tripped
Control unit incorrectly pro
grammed or set
Vitoair draught stabilizer defective
(only on boilers with pressure jet
burner)
Fault on control unit
No fuel
Control unit incorrectly pro
grammed or set
Cylinder temperature sensor defec
tive
Troubleshooting guide
Remedy
Switch on
Switch on mains electrical isolator
switch
Inform heating contractor
Check setting of heating program
and programming of the program
ming unit, and correct if necessary
Inform heating contractor. Change
setting of Vitoair to manual oper
ation:
Press in rotary knob A on motor
and turn fully beyond setting "4".
After consulting your heating con
tractor, the boiler can be operated
temporarily with constant boiler
water temperature by turning the
emissions test switch "S" to "h"
(see page 5) (leave cover open)
Oil/LPG:
Check fuel supply and re-order if
necessary.
Natural gas:
Open gas shut-off valve or contact
gas supply company if necessary.
Check time program for domestic
hot water heating (page 12 and 15),
check domestic hot water tempera
ture (page 18), and correct if neces
sary
Inform heating contractor
A
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