Viessmann Vitocal 350-A Installation And Service Instructions Manual page 140

Troubleshooting
Control unit diagnostics
Message
System characteristics Cause
«7A Room sensor HC3
■ No frost protection
mode via room temper-
ature sensor
■ No room temperature
hook-up
■ No room temperature
control
«92 Collector sensor
«93 Solar return sensor
«9A Collector sensor
«9B Solar return sensor
A4 Check valve
«A6 Secondary pump
140
(cont.)
Break, room temperature
sensor heating cir-
cuit M3
Short circuit, Vitosolic
collector temperature
sensor
Short circuit, Vitosolic
return temperature sen-
sor
Break, Vitosolic collector
temperature sensor
Break, Vitosolic return
temperature sensor
Solar check valve stuck
or faulty
No flow in secondary cir-
cuit (secondary circuit
pump stopped)
Measures
Check remote control
sensor and replace if
required (see Vitotrol
service instructions).
Check sensor and replace
if required (see Vitosolic
installation and service
instructions).
Check sensor and replace
if required (see Vitosolic
installation and service
instructions).
Check sensor and replace
if required (see Vitosolic
installation and service
instructions).
Check sensor and replace
if required (see Vitosolic
installation and service
instructions).
Inspect check valve and
replace if required (see
Vitosolic installation and
service instructions).
Test voltage at connection
2X8.7 and check secon-
dary pump mechanically;
replace if required.