Viessmann VITOCAL 300 Installation And Service Instructions Manual page 63

Control unit diagnostics
Fault messages
D4 Regulated HP 1
DA Room tempera-
ture sensor HC 1
DB Room tempera-
ture sensor HC 2
DD Room tempera-
ture sensor HC 1
GB Room tempera-
ture sensor HC 2
Reset the high limit safety cut-out
!
Please note
Touching 'live' components in
the working area can result in
the transfer of dangerous body
currents.
Ensure the device is at zero
volts before carrying out any
electrical work and before
resetting the high limit safety
cut-out.
(cont.)
Cause
Air inside the heating
circuit
Secondary pump or
heating circuit pump
stalled
Heating circuit con-
taminated
Short circuit
Lead broken
Note
The high limit safety cut-out is located
below the cover shielding the access
to the electrical terminals of the elec-
tric heater (at the bottom r.h. side of
the device).
1. Remove cover A.
2. Reset the high limit safety cut-out.
For this, push in the red button visi-
ble inside the aperture.
3. Fit cover A.
Troubleshooting
Measures
Vent the heating circuit
Check the secondary pump
or heating circuit pump
Flush the heating circuit
Check the sensor; replace if
required
Check the terminals; replace
the sensor, if required
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