Buderus 800 - Page 54

Servicing5
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
54
5.3.11 Replacing the mains-water sensor
 Unplug cable connection from mains-water sensor.
 Pull mains-water sensor out and push new unit in.
 Plug in cable connection.
5.3.12 Checking the cables to the flow, return and safety
sensors, and to the burner thermostat
Check to ensure that all plug-in connections to the
sensors/burner thermostat  and in the UBA  are in
order. Note that an incorrectly-inserted plug can lead to
the generation of error messages. Start up the boiler by
pressing the “reset” button.
 Set the mains switch to “0”.
 Disconnect the system from the power supply.
 Unplug the cable connection from the sensor/burner
thermostat.
 Check the cable between the plug-in connection and
the
24-pin plug in the UBA with a continuity tester.
 If the cables are in order, plug them in.
 Connect system to mains power supply.
 Set the mains switch to “I”.
fig. 69 Outside temperature sensor diagram
Outside temperature sensor
(˚C)
R (Ω)
0
5
10
15
20
25
-20
-15
-10
-5
50,00020,000 80,00040,00030,00010,000 60,000 70,000
fig. 70 Replacing the mains-water sensor
fig. 71 Checking the cable to the flow/return sensors
Rear side
of UBA
Flow sensor
Retur n sensor
Red wire slee ve