Baxi Combi 2 (224 Combi 2, 228 Combi 2, 224 Combi 2 LPG)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoNominal and range from Tab.24 (MI 7.4.3), front panel closed, same for both sizes. The MI 7.4.4 calibration table also gives 8.8 to 9.4% for NG. The Fig.54 combustion procedure flowchart instead accepts CO₂ between 8 and 9.6% at maximum rate, with no gas type stated. NG values are for G20 only: with G20 containing up to 20% hydrogen, set the gas valve by O₂ only. | 9.0% (8.8–9.4) | 10.3% (10.2–10.7) |
CO₂ at low rate More infoHide infoTab.24 (MI 7.4.3), front panel closed. The MI 7.4.4 calibration table also gives 8.1 to 8.6% for NG. The Fig.54 flowchart instead accepts CO₂ between 7.7 and 9.2% at minimum rate, and lower than the CO₂ at maximum rate, with no gas type stated. | 8.5% (8.1–8.6) | 9.7% (9.2–9.8) |
Maximum CO More infoHide infoTab.24 (MI 7.4.3) CO max, front panel closed, one figure with no rate stated. The Fig.54 flowchart accepts CO < 350 ppm at both maximum and minimum rate, with no gas type stated. | <250 ppm | <350 ppm |
CO/CO₂ ratio More infoHide infoMI 10.1 says to check the combustion performance (CO/CO₂ ratio) but gives no figure. | Not given in MI | Not given in MI |
O₂ at high rate More infoHide infoTab.24 (MI 7.4.3), front panel closed. The MI prints the range high to low. With G20 containing up to 20% hydrogen, O₂ may be about 1.5% higher; set the gas valve using the standard O₂ values for the gas used. | 4.8% (5.2–4.1) | 5.2% (5.4–4.6) |
O₂ at low rate More infoHide infoTab.24 (MI 7.4.3), front panel closed. The MI prints the range high to low. | 5.7% (6.5–5.6) | 6.1% (6.9–6.0) |
Working inlet pressure More infoHide infoNG from Fig.46 (MI 7.4.1), boiler at maximum rate: at the meter 19–23 mbar. MI 7.4.1 says the working pressure at the gas inlet test point (A) must be at least 18 mbar, and the permissible pressure drop across system pipework is ≤ 1 mbar. LPG: the MI gives only a supply pressure of 37 mbar for G31 (Tab.2, MI 3.1.3). Measurement point not stated in MI. Tab.2 gives the NG supply pressure as 20 mbar. |
| 37 mbar |
Gas rate at maximum More infoHide infoG20 and G31 Qmax from Tab.9 (MI 3.2.1). At minimum: G20 0.52 m³/h (224), 0.63 m³/h (228); G31 0.38 kg/h (224), 0.47 kg/h (228). The cover lists an LPG model for the 224 only, and Tab.24 gives no G31 settings for the 228, but Tab.9 still gives a 228 G31 figure. |
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Flue integrity More infoHide infoAt the air inlet sample point, boiler at maximum rate (MI 10.1 and Fig.54). | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 7791868 - 02 - 03122021
Enter service mode for high and low rate
High rate
Low rate
Models
| Model | Gas |
|---|---|
| 224 Combi 2 | NG |
| 228 Combi 2 | NG |
| 224 Combi 2 LPG | LPG |
Source: Baxi Installation and Service Manual, High-efficiency wall-hung condensing gas boiler, 224 Combi 2 - 228 Combi 2, 224 Combi 2 LPG, 7791868 - 02 - 03122021.
Sections: 3.1.3 Gas category (Tab.2); 3.2.1 Technical information (Tab.9); 5.4.12 Data plate; 7.4.1 Check the operational (working gas inlet pressure and gas rate); 7.4.2 Combustion parameters (chimney sweep function); 7.4.3 Service settings (Tab.24); 7.4.4 Calibrating the gas valve; Fig.54 Combustion procedure; 10.1 General.
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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.