British Gas CS1 system (ZB 7-28 CS1)
System boiler, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoAt max. rated heat output (service mode display 2.). Table 14 and the technical data (Table 2) agree. No tolerance given. The gas/air ratio is factory set and no adjustment is needed for natural gas (MI 5.1, 6.3); it may only be adjusted on the basis of a CO₂ measurement at max. and min. heat output. | 9.2% | 10.8% |
CO₂ at low rate More infoHide infoAt min. rated heat output (service mode display 1.). Table 14 and the technical data (Table 2) agree. No tolerance given. | 8.8% | 10.5% |
Maximum CO | Not given in MI | Not given in MI |
CO/CO₂ ratio | Not given in MI | Not given in MI |
O₂ | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoChecked at the gas supply pressure test point (MI fig. 2, item 7), which the drawing shows on the gas valve. NG must not be operated below 18 or above 24 mbar. MI 5.1 says LPG must not be operated if the supply pressure is not 37 mbar at the inlet to the appliance; MI 7 says below or above 37 mbar at the test point. Technical data (Table 2) gives gas supply pressure NG 20 mbar, LPG 37 mbar. |
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Gas rate at maximum More infoHide infoAfter 10 minutes from lighting. NG G20 CVnet 34.02 MJ/m³; LPG CVnet 88 MJ/m³. | 2.9 m³/h | 2.1 kg/h |
Flue integrity More infoHide infoIn the combustion air, at the combustion air testing point (234.1), in chimney sweep mode (max. rated heat output or the set heating output). For type C13 or C33 flue systems. | O₂ not less than 20.6% CO₂ not more than 0.2% | O₂ not less than 20.6% CO₂ not more than 0.2% |
From 6 720 610 601 GB (03.02)
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 |
|---|---|---|
| ZB 7-28 CS1 | 41-108-02 | NG |
Source: British Gas CS1 Installation and Servicing Instructions, wall mounted condensing boiler for central heating, 6 720 610 601 GB (03.02).
Sections: 1.6 Layout of appliance; 1.9 Technical data; 5.1 Commissioning; 6.3 Setting the gas/air ratio; 7 Checking the gas supply pressure; 7.1 Setting the gas/air ratio; 7.2.1 Testing the O2 or CO2 level in the combustion air; 7.2.2 Testing CO and CO2.
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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.