Viessmann VITOCAL 242-G Installation And Service Instructions Manual page 129

Control unit diagnostics
Fault messages
D3 Safety chain
D5 DHW SHC
D7 E heating K6
D8 E heating K7
D9 E heating K8
DA Room sensor
HC1
DB Room sensor
HC2
DD Room sensor
HC1
DE Room sensor
HC2
(cont.)
Cause
Fault at one of the con-
nected components
Break in jumper X 6.5
6.6
Check the heating ele-
ments connected to K6
Check the heating ele-
ments connected to K7
Check the heating ele-
ments connected to K8
Short circuit
Lead broken
Troubleshooting
Measures
External safety chain;
check connected compo-
nents and circuits (e.g.
brine pressure or jumper)
X Check any possibly con-
nected switching contact or
bridge (connection on the
power PCB)
Note
Ensure the equipment is at
zero volt before resetting
the high limit safety cut-out.
To restart the system, reset
the relevant high limit safety
cut-out on the heater rod
(for this, press the red but-
ton).
Note
The high limit safety cut-
outs are located on the front
and back of the heater rods;
see also the diagram on
page 130.
Check the sensor and re-
place, if required
Check the terminals and re-
place the sensor, if required
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