Baxi Baxi Combi (224, 228, 424, 428)
Combi, natural gas
Combustion figures
| Figure | Natural gas (G20) |
|---|---|
CO₂ at high rate More infoHide infoFrom Setting the gas valve (MI 10.3.7). Case front panel fitted, boiler run for several minutes in chimney sweep mode at maximum rate, probe in the flue sample point. If CO₂ is reset at one rate, recheck the other. | 9% +0.4, −0.2 |
CO₂ at low rate More infoHide infoFrom Setting the gas valve (MI 10.3.7), boiler at minimum rate in chimney sweep mode. | 8.5% +0.1, −0.4 |
Maximum CO More infoHide infoSame limit at maximum and minimum rate (Fig.44 combustion procedure). | <350 ppm |
CO/CO₂ ratio More infoHide infoSame limit at maximum and minimum rate (Fig.44, MI 10.1 and 10.3.7). | <0.004 |
O₂ | Not given in MI |
Working inlet pressure More infoHide infoFrom Fig.40 (MI 7.4.1). At the meter: 19–23 mbar. Permissible pressure drop across system pipework ≤ 1 mbar. MI 7.4.1 text also says the working pressure at the inlet test point on the gas cock (Fig.41), at maximum rate, must be AT LEAST 17 mbar, which is lower than the 18–22 mbar Fig.40 shows at the gas cock. Tab.8 gives a nominal inlet pressure of 20 mbar (G20). |
|
Gas rate at maximum More infoHide infoTab.25 and Tab.8 agree. Measure with all other appliances and pilot lights off. Tab.8 gives a minimum gas rate (Qmin) of 0.52 m³/h for all models. |
|
Flue integrity More infoHide infoAt the air inlet test point on the flue adaptor, boiler at maximum rate. | O₂ ≥ 20.6% CO₂ < 0.2% |
From 7661586 - 2 - 12072016
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 Combi 224 | 47-077-21 | NG |
| Baxi Combi 228 | 47-077-22 | NG |
| Baxi Combi 424 | 47-077-23 | NG |
| Baxi Combi 428 | 47-077-24 | NG |
Source: Baxi Combi 224, 228, 424, 428 Installation and Service Manual, 7661586 - 2 - 12072016.
Sections: 3.2 Technical data (Tab.5, Tab.8); 7.4.1 Check the operational (working gas inlet pressure and gas rate); 7.4.2 Checking combustion - chimney sweep mode; 10.1 General; 10.3.7 Air/gas unit (Setting the gas valve); 14.1 Combustion check on small heating systems.
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.