Buderus Logamax GB062-24 KDE H V2 Service Manual page 27

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
1. Is the system water pressure in green
area (1 - 2 bar) ?
2. Is the circulation pump blocked or
problem voltage supply ?
3. Are the flue gas temperature limiter
(STB) cables disconnected ?
B Switch off the boiler.
4.
B Remove the flue gas temperature
limiter (STB) connection cables.
B Measure the flue gas temperature
limiter (STB).resistance.
Is there circuit open?
Logamax PLus GB062
Step
yes: -->2.
B Add or correct the system water pressure.
no:
B Bleed the air in system.
B Make RESET and start the boiler again.
4C ? --> 2.
yes: B Remove the blockage (turn the pump shaft).
If no result :
B Switch off the boiler and cut the main supply.
B Drain of he water in boiler.
B Check the fuses. if OK, change the circulation pump.
B Refill the system again and bleed the air.
B Switch on the main supply and the boiler.
4C ? --> 3.
no: --> 3.
B Switch off the boiler.
yes:
B Connect the cables.
B Switch on the boiler.
4C ? --> 4.
no: --> 4.
B Change the flue gas temperature limiter (STB).
yes:
B Connect the cables.
B Switch on the boiler.
4C ? --> 5.
no: B Connect the flue gas temperature limiter (STB) cables.
B Switch on the boiler.
--> 5.
4
Fault finding
27