Buderus Logamax GB062-24 KDE H V2 Service Manual page 28

4
Fault finding
4C
- Heat exchanger temperature limiter or flue gas temperature limiter has tripped.
- The differential pressure switch does open when the fan runs (after ignition) (only high modulation version).
Step
5. Are the heatexchanger temperature
limiter (STB) cables disconnected or
loose?
B Switch off the boiler.
6.
B Remove the heat exchanger
temperature limiter (STB) connection
cables.
B Measure the heat exchanger
temperature limiter (STB).resistance.
Is there circuit open?
7. B Switch off the boiler.
B Remove the front cover and first
visual check of main heat exchanger
(WB6) for damages, corrosions or
rippen effect.
B Measure the actuating pressure for
the maintenance necessity (Steuer-
druck). if the pressure not OK. Clean
the WB6 (see capital in IM for the
maintenace pressure).
Is the main heat exchanger (WB6)
visual and pressure OK ?
B Switch off the boiler.
8.
B Check the connection cables and the
diff. pressure switch itself.
Is the circuit open (default closed) ?
28
Step
yes: B Switch off the boiler..
B Connect the cables again.
B Switch on the boiler.
4C ? --> 6.
no: --> 6.
B Change the heat exchanger temperature limiter (STB).
yes:
B Connect the cables again.
B Switch on the boiler.
4C ? --> 7.
B Connect the heat exchanger temperature limiter (STB)
no:
cables.
B Switch on the boiler.
--> 7.
yes: 4C ? --> 8.
no: B Clean the WB6. Check the burner, upper and down
buffels (inside WB6). If there any damages on WB6,
change it.
B Refill the system with water.
B Switch on the boiler.
--> 8.
yes: 4C ? --> 9.
no: B Correct the cable or connection. If necessary, change
the diff. pressure switch.
B Switch on the boiler.
--> 9.
Logamax Plus GB062