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14.0 Servicing the Boiler
39
© Baxi Heating UK Ltd 2011
14.1 Annual Servicing
WARNING: The PCB Control and Fan
Assembly are 325 Vdc. Isolate system controls
before access.
IMPORTANT: When servicing ensure that both the gas and
electrical supplies, including Switched and Permanent Live to the
boiler are isolated before any work is started.
The four LEDs on the facia will all be OFF.
It is important to isolate the electrical supply at the system
isolation switch as it is not possible to do this on the boiler itself.
Hazardous materials are not used in the construction of this
product, however reasonable care during service is
recommended - see Section 1.2.
When replacing the combustion box door after servicing it is
essential that the retaining screws are tightened fully.
1. For reasons of safety and economy, it is recommended that
the boiler is serviced annually. Servicing must be performed by a
competent person in accordance with B.S. 7967-4.
2. After servicing, complete the relevant Service Interval Record
section of the Benchmark Commissioning Checklist at the rear of
this publication.
IMPORTANT:During routine servicing, and after any
maintenance or change of part of the combustion circuit, the
following must be checked:-
•The integrity of the complete flue system and the flue seals.
•The integrity of the boiler combustion circuit and relevant
seals as described in Section 14.2.
•The operational gas inlet pressure as described in Section
12.2.1 to 12.2.3 and the gas rate as described in 12.2.4.
•The combustion performance as described in ‘Check the
Combustion Performance’ (14.1.4 to 14.1.6 below).
3. Competence to carry out Checking Combustion
Performance
B.S. 6798 ‘Specification for Installation & Maintenance of Gas
Fired Boilers not exceeding 70kW’ advises that:-
• The person carrying out a combustion measurement should
have been assessed as competent in the use of a flue gas
analyser and the interpretation of the results.
• The flue gas analyser used should be one meeting the
requirements of BS7927 or BS-EN50379-3 and be calibrated
in accordance with the analyser manufacturers’ requirements.
• Competence can be demonstrated by satisfactory
completion of the CPA1 ACS assessment, which covers the
use of electronic portable combustion gas analysers in
accordance with BS 7967, Parts 1 to 4.
Check the Combustion Performance (CO/CO
2
ratio)
4. Set the boiler to operate at maximum rate as described in
Section 12.2.
5. Remove the cap from the flue sampling point, insert the
analyser probe and obtain the CO/CO
2
ratio. This must be
less than 0.004.
6. If the combustion reading (CO/CO
2
ratio) is greater than
this, and the integrity of the complete flue system and
combustion circuit seals has been verified, and the inlet gas
pressure and gas rate are satisfactory either:
•Perform the ‘Annual Servicing - Inspection’ (Section 14.2) &
re-check.
•Replace the gas valve (Section 15.8) & re-check.