Buderus Logamax GB062-24 KDE H V2 Service Manual page 20

4
Fault finding
3Y
The differential pressure switch is open before ignition (during self check) (only high modulation version).
Steps
1. Check the contacts of diff. pressure
switch.
B Switch off the boiler.
B Check the connection of diff. pressure
switch.
B Measure the circuit with a instrument.
The circuit /contact should be closed.
Is the contact /circuit open ?
2. Check the silicon hose.
Is there any blockage or stuck on silikon
hose ?
3. Check the low voltage cable for damages
or open circuit.
B Switch off the boiler.
B Remove the connection of PCB and
measure the circuit of the diff.
pressure switch.
B Measure the circuit with a instrument.
The circuit /contact should be closed.
Is the contact /circuit open ?
4. Electronic board (PCB) is defect.
20
Remedy
yes: B Change the diff. pressure switch.
B Switch on the boiler.
3Y ? -->2.
B Connect the diff. pressure switch again.
no:
B Switch on the boiler.
-->2.
B Switch off the boiler.
yes:
B Change the silicon hose or correct the stuck.
B Switch on the boiler.
3Y ? -->3.
no: -->3.
B Change the low valtage cable.
yes:
B Switch on the boiler.
3Y ? --> 4.
no: --> 4.
B Switch off the boiler.
B Cut the main voltage supply.
B Change the electronic board (PCB).
B Switch on the main voltage supply.
B Switch on the boiler.
B END
Logamax Plus GB062