10 Maintenance
10.1 General
Warning
When changing components ensure that both the gas and
electrical supplies to the boiler are isolated before any work is
started. When the component has been changed recommission
the boiler.
Always examine any seals or gaskets, replacing where necessary.
The case front panel MUST seal effectively against the boiler side
panels.
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 BS 7967-4.
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 by checking
air inlet sample to eliminate the possibility of recirculation. O
2
≥ 20.6% &
CO
2
< 0.2%
The integrity of the boiler combustion circuit and relevant seals.
The operational gas inlet pressure and the gas rate.
The combustion performance as described in "Check the Combustion
Performance" below.
Competence to carry out checking combustion performance BS 6798
"Specification for Installation & Maintenance of Gas Fired Boilers not
exceeding 70kWh" 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
BS 7927 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)
Set the boiler to operate at maximum rate.
See
Checking combustion - chimney sweep mode, page 48 for details.
Remove the plug from the flue sampling point, insert the analyser probe
and obtain the CO/CO
2
ratio. This must be less than 0.004. 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 "Standard Inspection and Maintenance" .
Perform "Setting the Gas Valve" .
Replace and set the gas valve.
10 Maintenance
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