Baxi Baxi Combi 2 (424 Combi 2, 430 Combi 2, 424 Combi LPG 2, 430 Combi LPG 2)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoNominal and range of tolerance at Pn Max, front panel closed (Tab.24). Same for 424 and 430. Section 7.4.4 also gives NG 8.8 to 9.4% at maximum heat input, with the boiler in chimney sweep high mode H. For G20 with up to 20% hydrogen, calibrate the gas valve using O₂ only. The combustion procedure flowchart (Fig.54, MI p. 48) instead gives CO₂ between 8 and 9.6% at maximum rate, without saying which gas. The manual prints decimal commas (e.g. 9,0%); shown here with points. | 9.0% (8.8 - 9.4) | 10.3% (10.2 - 10.7) |
CO₂ at low rate More infoHide infoNominal and range of tolerance at Pmin, front panel closed (Tab.24). Section 7.4.4 prints the NG range at minimum heat input as 8 1 to 8.6 (decimal point missing in print), which matches Tab.24. The combustion procedure flowchart (Fig.54, MI p. 48) instead gives CO₂ between 7.7 and 9.2% at minimum rate, and lower than at maximum rate, without saying which gas. | 8.5% (8.1 - 8.6) | 9.7% (9.2 - 9.8) |
Maximum CO More infoHide infoCO max, front panel closed (Tab.24). The combustion procedure flowchart (Fig.54, MI p. 48) instead gives CO under 350 ppm at both rates, without saying which gas. | <250 ppm | <350 ppm |
CO/CO₂ ratio | Not given in MI | Not given in MI |
O₂ at high rate More infoHide infoNominal and range of tolerance at Pn Max, front panel closed (Tab.24). The MI says 20% hydrogen in G20 can raise O₂ in the flue gases by about 1.5%. | 4.8% (5.2 - 4.1) | 5.2% (5.4 - 4.6) |
O₂ at low rate More infoHide infoNominal and range of tolerance at Pmin, front panel closed (Tab.24). | 5.7% (6.5 - 5.6) | 6.1% (6.9 - 6.0) |
Working inlet pressure More infoHide infoNG: from Fig.46, with the boiler at maximum rate in chimney sweep. The MI says the pressure at the inlet gas pressure test point (gas inlet A) must be at least 18 mbar. At the meter: 19–23 mbar. Nominal supply pressure 20 mbar (Tab.2). LPG: supply pressure from Tab.2 only, with no working range given. Measurement point not stated in MI. |
| 37 mbar |
Gas rate at maximum More infoHide infoG20 and G31 gas consumption (Qmax), Tab.9. NG figures at 20 mbar with a CV of 37.78 MJ/m³. |
|
|
Flue integrity More infoHide infoAt the air inlet sample point (combustion air intake socket B). | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 7791870 - 03 - 15032022
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
| Model | Gas |
|---|---|
| 424 Combi 2 | NG |
| 430 Combi 2 | NG |
| 424 Combi LPG 2 | LPG |
| 430 Combi LPG 2 | LPG |
Source: Baxi Installation and Service Manual, High-efficiency wall-hung condensing gas boiler, 424 Combi 2 - 430 Combi 2, 424 Combi LPG 2 - 430 Combi LPG 2, 7791870 - 03 - 15032022.
Sections: 3.1.3 Gas category; 3.2.1 Technical information (Tab.9 Combustion characteristics); 7.4.1 Check the operational (working gas inlet pressure and gas rate); 7.4.2 Combustion parameters; 7.4.3 Service settings; 7.4.4 Calibrating the gas valve; 10.1 General.
Spotted something wrong? Tell us.
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.