SECTION 10 - COMBUSTION CHECK
FLOWCHART FOR CO LEVEL AND COMBUSTION RATIO
CHECK ON COMMISSIONING A CONDENSING BOILER
Important Preliminary Information on Checks
The air gas ratio valve is factory-set and must not be adjusted DURING COMMISSIONING.
PRIOR TO CO LEVEL AND COMBUSTION RATIO CHECK
The installation instructions must have been followed, gas type verified and gas supply pressure / gas rate checked as
required prior to commissioning.
As part of the installation process, ESPECIALLY WHERE A FLUE HAS BEEN FITTED BY PERSONS OTHER THAN
THE BOILER INSTALLER, visually check the integrity of the whole flue system to confirm that all components are
correctly assembled, fixed and supported. Check that maximum flue lengths have not been exceeded and all guidance
has been followed (e.g. Gas Safe Register Technical Bulletin (TB) 008 where chimney/flues are in voids).
The ECGA should be of the correct type, as specified by BS 7967.
Prior to its use, the ECGA should have been maintained and calibrated as specified by the manufacturer. The installer
must have the relevant competence for use of the analyser.
Check and zero the analyser IN FRESH AIR in accordance with the analyser manufacturer’s instructions.
CO = carbon monoxide
= carbon dioxide
O2 = oxygen
Combustion Ratio = The CO reading measured in ppm divided by the CO
reading first converted to ppm
ppm = parts per million
GS(I&U)R = Gas Safety (Installation and Use) Regulations
*Setting to Minimum Rate:
1. Turn the CH temperature control knob to the 11 O’clock position.
2. Create a CH demand by ensuring that the system controls are requesting heat and the boiler Mode
Knob is in the Winter Position.
3. Within an overall time of 3 seconds, turn the CH temperature control knob fully clockwise, back to
11 O’clock and then fully clockwise again.
4. “S” will be shown on the display and the boiler output will be reduced to minimum
5. The boiler will remain at minimum rate for 5 minutes before reverting to normal operation