Buderus 800 - Page 51

Servicing 5
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
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5.3.7 Checking the modulating pump
 Unscrew the plug on the modulating pump.

Set the mains switch to “I”.
 Check to ensure that the modulating pump is run-
ning.
The modulating pump’s running mechanism may be-
come blocked if the heating system has been out of
use for an extended period.
 If the modulating pump fails to run:
Set the mains switch to “0”.
 Use a spanner to rotate the modulating pump in its
normal running direction. If this fails to unblock the
mechanism, the modulating pump is defective.
 If the modulating pump is working correctly, screw
the plug in.
5.3.8 Replacing the modulating pump
 Disconnect the system from the power supply
(fig. 62, item 1).
 Close maintenance isolating valves.
 Drain the 800 Series.
 Loosen screws on modulating pump terminal box
and open terminal box (fig. 62, item 2).
 Loosen cable (fig. 63, item 1).
Note order of cable terminals.
 Loosen modulating pump screw-in adapters and re-
move pump (fig. 62, item 3).
 Fit new pump and connect to system (fig. 62, item 4).
Ensure when doing so that the heat-exchanger spac-
er washer is inserted correctly.
 Connect cables in correct order inside terminal box,
close terminal box and screw shut.
fig. 61 Checking the modulating pump
CAUTION!
Water will flow out.
fig. 62 Replacing the modulating pump
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