Viessmann VITODENS 200 WB2A, Installation & Servicing Instructions Manual

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8 Fault Finding
Features are as follows:
Troubleshooting steps
Diagnosis
Establish error message or determine behaviour of system.
Look for the corresponding cause of the fault in the diagnostic table.
Correction
Establish the action required in the table.
Correct the fault.
a)
The mains electrical supply is turned on.
b)
The clock and / or room thermostat (if fitted) are calling for heat (CH ‘faults’ only)
c)
The gas service cock is open.
d)
The DHW (Combi only) and CH isolation cocks are open.
e)
The system is at design pressure.
Before attempting any electrical fault finding, always conduct the preliminary electrical system
checks as described in the Instructions for the British Gas Multimeter or other similar
instrument.
On completion of any service or fault finding operation involving making or breaking electrical
connections always check for EARTH CONTINUITY, POLARITY and RESISTANCE TO EARTH.
Detailed procedures for replacing faulty components are described in section 9.
8.1 General
8.2 Built in Diagnostic Features
Before looking for a fault condition, check that:
It is the law that any service work must be carried out by a competent person such as a British
gas engineer or other CORGI registered personnel
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