6 720 611 137 GB (03.02)
34
Maintenance
8.2
Description of servicing operations
The combustion performance must be checked before
and after any servicing work on the combustion and
burner components. Refer to section 7.2.
Check “Last fault stored”:
B
Select Service Function .0 (see page 26 “Selecting
Service Function”).
There is a list of the fault codes in the Appendix (see
page 40.
To delete “Last fault stored”:
B
Turn function control anti-clockwise as far as the
stop.
B
Press and hold the
button until the display
shows [ ].
The last fault stored has now been deleted.
Checking the ionisation current,
Service Function 3.3
B
Select Service Function 3.3 (see page 26 “Selecting
Service Function”).
If the display shows 2 or 3, the ionisation current is OK.
If the display shows 0 or 1, the electrode assembly
(32.1, page 6) must be cleaned or replaced.
Primary Heat exchanger
There is a special accessory kit (no. 840) for cleaning
the heat exchanger, order no. 7 719 001 996.
B
Check control pressure on the air - gas mixer unit at
max. rated heat output using an electronic manome-
ter.
Fig. 48
B
B
Unscrew condensation trap and place suitable con-
tainer underneath. Refer to fig. 49.
B
Remove the fan and the burner as described in the
text headed “Burner” (see page 35).
Fig. 49
B
Loosen any deposits in the heat exchanger from top
to bottom using the cleaning blade. Refer to fig. 50.
Fig. 50
B
Clean the heat exchanger from top to bottom using
the brush. Refer to fig. 51.
Fig. 51
B
Flush the heat exchanger from the top. Refer to
fig. 52.
i
The heat exchanger should only be
cleaned if the control pressure is
2.2 mbar (depression) or less.
6 720 610 332-69.1R
6 720 610 332-72.1R
6 720 610 332-73.1R
6 720 610 332-74.1R
