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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 7.1.
Check "Last fault stored":
B Select Service Function .0 (see page 28 "Selecting
service function").
There is a list of the fault codes in the Appendix (see
page 42).
To delete "Last fault stored":
B Turn temperature control
the stop.
B Press and hold the
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 28 "Select-
ing 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.
2 .
1 .
Fig. 51
The heat exchanger should only be
i
cleaned if the control pressure is
4.2 mbar (depression) or less.
B Remove cleaning access cover (415, page 6) and
the metal plate below it, if present. Refer to fig. 2.
B Unscrew condensation trap and place suitable con-
tainer underneath. Refer to fig. 52.
6 720 611 443 GB (05.04)
anti-clockwise as far as
button until the display
B Remove the fan and the burner as described in the
text headed "Burner" (see page 36).
Fig. 52
B Loosen any deposits in the heat exchanger from top
to bottom using the cleaning blade. Refer to fig. 53.
Fig. 53
B Clean the heat exchanger from top to bottom using
the brush. Refer to fig. 54.
Fig. 54
B Flush the heat exchanger from the top. Refer to
fig. 55.
Maintenance
6 720 610 332-72.1R
6 720 610 332-73.1R
6 720 610 332-74.1R
35
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