Viessmann Vitocal 300-G Installation And Service Instructions Manual page 122

Troubleshooting
Control unit diagnostics
ID Message
(priority)
38 Flow sens. pri-
mary ("U")
39 Return sens.
primary ("U")
40 Flow temp.
sens HK2 ("U")
41 Flow temp.
sens HK3 ("U")
43 Flow sens.
system ("U")
44 Flow temp.
sens NC ("U")
48 Flow temp.
sens HK2 ("U")
49 Flow temp.
sens HK3 ("U")
4B Flow sens.
system ("U")
4C Flow temp.
sens NC ("U")
122
(cont.)
1. Cause
2. Measures
1. Break, primary flow temperature
sensor (IN)
2. Check the sensor and replace, if
required
1. Break, primary return temperature
sensor (OUT)
2. Check the sensor and replace, if
required
1. Short circuit, flow temperature sen-
sor, heating circuit 2 (mixer circuit)
2. Check the sensor and replace, if
required
1. Short circuit, flow temperature sen-
sor, heating circuit 3 (mixer circuit)
2. Check the sensor and replace, if
required
(see installation instructions KM BUS
mixer)
1. Short circuit, system flow
2. Check the sensor and replace, if
required
1. Short circuit, flow temperature sen-
sor NC
2. Check the sensor and replace, if
required
1. Break, flow temperature sensor,
heating circuit 2
2. Check the sensor and replace, if
required
1. Break, flow temperature sensor,
heating circuit 3
2. Check the sensor and replace, if
required
(see installation instructions KM BUS
mixer)
1. Break, system flow
2. Check the sensor and replace, if
required
1. Break, flow temperature sensor NC
2. Check the sensor and replace, if
required
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right
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