Baxi Checked against MI

Baxi Baxi Combi 100 (124, 128)

Combi, natural gas and LPG

Combustion figures

Figure	Natural gas (G20)	LPG (G31)
CO₂ at high rate More infoHide info Section 14.1 gives the same figure at maximum (100), the ignition phase speed and minimum (00). Don’t insert the probe straight away, to avoid saturating the analyser.	9.0% ± 0.7	10.5% ± 1.0
CO₂ at low rate More infoHide info Same figure as at high rate (section 14.1).	9.0% ± 0.7	10.5% ± 1.0
Maximum CO More infoHide info From the section 10.2 commissioning flow chart, which doesn’t separate natural gas and propane.	Max rate < 350 ppm Min rate < 350 ppm	Max rate < 350 ppm Min rate < 350 ppm
CO/CO₂ ratio More infoHide info From the section 10.2 flow chart; section 12.1 also says the ratio must be less than 0.004. Neither separates natural gas and propane.	Max rate < 0.004 Min rate < 0.004	Max rate < 0.004 Min rate < 0.004
O₂	Not given in MI	Not given in MI
Working inlet pressure More infoHide info NG ranges are from the section 10.3 diagram (gas cock 18–22, gas valve 17–21, meter 19–23 mbar), boiler at maximum. Section 10.3 also says the working pressure at the inlet test point on the gas cock or valve must be at least 17 mbar (LPG 37 mbar). LPG figure is from fault finding chart G (supply pressure at the gas valve). Technical data 4.1 gives inlet pressure 20 mbar (NG) and 37 mbar (propane) without saying where; section 17.1 gives a preferred minimum of 20 mbar (NG) and 37 mbar (LPG).	Appliance inlet 18–22 mbar Gas valve test point 17–21 mbar	Gas valve test point Minimum 37 mbar
Gas rate at maximum More infoHide info The manual contradicts itself on the 124 propane gas rate: technical data 4.1 gives 1.96 kg/h, section 10.3 gives 1.94 kg/h. Technical data figures are after 10 minutes; section 10.3 says measure with other appliances and pilot lights off.	124 2.61 m³/h 128 3.05 m³/h	124 1.96 kg/h (section 4.1) or 1.94 kg/h (section 10.3) 128 2.29 kg/h
Flue integrity More infoHide info At the air inlet test point, boiler at maximum rate (section 10.2 flow chart).	O₂ ≥ 20.6% CO₂ < 0.2%	O₂ ≥ 20.6% CO₂ < 0.2%

From 7659607-02 (04/17)

Enter service mode for high and low rate

High rate

Steps not added yet. Follow the MI.

Low rate

Steps not added yet. Follow the MI.

Ending the test: follow the MI.

Models and GC numbers

Model	GC number	Gas
Baxi 124 Combi	47-077-25	Not stated
Baxi 128 Combi	47-077-26	Not stated

Source: Baxi 124 - 128 Combi condensing combination boiler installation and service manual, 7659607-02 (04/17).

Sections: 1.1 Description; 4.1 Technical data; 10.1 Commissioning the boiler; 10.2 Checking the combustion - Chimney Sweep function; 10.3 Check the operational (working) gas inlet pressure & gas rate; 12.1 Performance safety check & annual servicing; 14.1 Checking the combustion; 14.3 Adjusting the CO₂; 17.1 Initial fault finding checks; 17.0 Fault finding chart G.

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Check these figures against the MI for the appliance in front of you, matched by GC number and manual date. Combustion work needs a calibrated analyser and a Gas Safe registered engineer.