Vaillant home combi, Installation And Maintenance Instructions Manual

Appendix

46

Installation and maintenance instructions HOME 0020224355_00

J

Combustion chart

PRIOR TO CO AND COMBUSTION RATIO CHECK

The boiler manufacturer’s installation instructions should have been followed, gas type verified and gas 

supply pressure/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 manufacturer’s max. flue lengths have not been 

exceeded and all guidance has been followed (e.g. Gas Safe Technical Bulletin TB008).

The flue gas analyser should be of the correct type, as specified by BS 7967

Prior to its use, the flue gas analyser 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 as per analyser manufacturer’s instructions.

NOTE

THE AIR GAS RATIO VALVE IS FACTORY 

SET AND MUST NOT BE ADJUSTED 

DURING COMMISSIONING UNLESS THIS 

ACTION IS RECOMMENDED FOLLOWING 

CONTACT WITH THE MANUFACTURER.

If any such adjustment is recommended and 

further checking of the boiler is required the 

installer/service engineer must be competent 

to carry out this work and to use the flue gas 

analyser accordingly.

If the boiler requires conversion to operate with 

a different gas family (e.g. conversion from 

natural gas to LPG) separate guidance will be 

provided by the boiler manufacturer

 CARRY OUT FLUE INTEGRITY CHECK USING ANALYSER

Insert analyser probe into air inlet test point and allow readings to stabilise.

NOTE

 - where no air inlet test point is provided then a flue integrity check 

with the analyser is not possible. The installer should verify that flue 

integrity has been visually checked in accordance with the 

“Prior to CO 

and combustion ratio check”

 box above before proceeding to the 

“Check CO and combustion ratio at maximum rate” 

stage below.

SET BOILER TO MINIMUM RATE

In accordance with boiler instructions, set boiler to operate at minimum rate (to 

minimum load condition). Allow sufficient time for combustion to stabilise.

NOTE 

- If manufacturer’s instructions do not specify how to set boiler to minimum 

rate contact Technical Helpline for advice.

CHECK CO AND COMBUSTION RATIO AT MINIMUM RATE

With boiler still set at minimum rate, insert analyser probe into flue gas sampling 

point. Allow readings to stabilise before recording.

NOTE 

- If no flue gas sampling point is present and the correct procedure is not 

specified in the manual, consult boiler manufacturer for guidance.

CHECK CO AND COMBUSTION RATIO AT MAX. RATE

With boiler still set at maximum rate, insert analyser probe into flue gas 

sampling point. Allow readings to stabilise before recording.

NOTE 

- If no flue gas sampling point is present and the correct procedure is 

not specified in the manual, consult boiler manufacturer for guidance.

SET BOILER TO MAXIMUM RATE

In accordance with boiler instructions, set boiler to operate at max. rate 

(full load condition). Allow sufficient time for combustion to stabilise.

NOTE - Do not insert analyser probe during this period to avoid 

possible “flooding” of sensor.

Is

CO less than 

350ppm and

CO/CO

2

 ratio

less than 0.004

Is

O

2

 ≥ 20.6%

and

CO

2

 < 0.2%

Is

CO less than 

350ppm and

CO/CO

2

 ratio

less than 0.004

BOILER IS OPERATING SATISFACTORILY

no further actions required.

Ensure test points are capped, boiler case is correctly replaced and 

all other commissioning procedures are completed.

Complete Benchmark Checklist, recording CO and combustion ratio 

readings as required.

TURN OFF APPLIANCE AND CALL 

MANUFACTURER’S TECHNICAL HELPLINE 

FOR ADVICE.

THE APPLIANCE MUST NOT BE 

COMMISSIONED UNTIL PROBLEMS ARE 

IDENTIFIED AND RESOLVED.

 VERIFY FLUE INTEGRITY

Analyser readings indicate that combustion products 

and inlet air must be mixing. Further investigation of 

the flue is therefore required.

Check that flue components are assembled, fixed 

and supported as per boiler/flue manufacturer’s 

instructions.

Check that flue and flue terminal are not obstructed.

Is

CO

less than 

335ppm

and

CO/CO

2

 ratio less 

than 0.004

Is

O

2

 ≥ 20.6%

and

CO

2

 < 0.2%

Check all seals around the appliance burner, 

internal flue seals, door and case seals. 

Rectify where necessary.

TURN OFF APPLIANCE AND CALL 

MANUFACTURER’S TECHNICAL HELPLINE 

FOR ADVICE.

THE APPLIANCE MUST NOT BE 

COMMISSIONED UNTIL PROBLEMS ARE 

IDENTIFIED AND RESOLVED. IF 

COMMISSIONING CANNOT BE FULLY 

COMPLETED, THE APPLIANCE MUST BE 

DISCONNECTED FROM THE GAS SUPPLY IN 

ACCORDANCE WITH THE GSIUR.

NOTE: 

Check and record CO and combustion ratio 

at both max. and min. rate before contacting the 

manufacturer.

NO

NO

NO

NO

NO

YES

YES

YES

YES

YES