Worcester Bosch Greenstar Si Compact ErP combi (25Si, 30Si)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoFrom Tables 26 and 27 (MI 7.6), maximum setting, measured after 10 minutes in chimney sweep mode. The technical data (MI 3.3, Table 5) gives 9.1% (NG) and 10.6% (LPG) at maximum, after 10 minutes. The MI says the gas valve is factory set and must not be adjusted during commissioning if found out of tolerance: call the Worcester help line (MI 6.7). If CO₂ is still out of tolerance after all the checks in MI 7.6, the gas valve must be replaced. | Between 8.5 and 10.1% | Between 9.8 and 11.1% |
CO₂ at low rate More infoHide infoFrom Tables 26 and 27 (MI 7.6), minimum setting, measured after 10 minutes. The manual contradicts itself: its worked example for NG says that with a maximum reading of 9.5% the minimum must be between 8.0% and 9.3%, but Table 26 only asks for above 7.5%. Both shown as printed. The technical data (MI 3.3, Table 5) gives 8.5% (NG) and 9.6% (LPG) at minimum, after 10 minutes. | A minimum 0.2 lower than the maximum reading taken but above 7.5% | A minimum 0.2 lower than the maximum reading taken but above 8.5% |
Maximum CO More infoHide infoThe manual gives different limits. The combustion check flow chart (MI 6.7, Fig. 59) says CO < 350ppm at maximum and minimum rate. Tables 26 and 27 (MI 7.6) give less than 200ppm at maximum and less than 50ppm at minimum. All shown as printed. |
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CO/CO₂ ratio More infoHide infoFrom the combustion check flow chart (MI 6.7, Fig. 59), at maximum and minimum rate. MI 6.5.2 says the technical data gives CO/CO₂ ratios, but Table 5 doesn’t list one, and Tables 26 and 27 (MI 7.6) don’t give one either. | < 0.004 | < 0.004 |
O₂ | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoFrom Figs. 56 and 57 (MI 6.5.1) and the table in MI 7.4, boiler running at maximum in chimney sweep mode. At the meter: NG 19–23 mbar. At the regulator: LPG 32–45 mbar. Allowed drop across the pipework: 1 mbar (NG), 2.5 mbar (LPG); across the boiler: 1.5 mbar. The drop from the meter to the gas valve inlet test nipple must be no more than 2.5 mbar (NG) or 4 mbar (LPG). |
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Gas rate at maximum More infoHide infoMax. 10 minutes from lighting, NG figures for G20 (MI 3.3, Table 5, where the sizes are headed 25kW and 30kW). Measure at the gas meter after at least 10 minutes at maximum output (MI 6.5.2). Where there’s no gas meter (e.g. LPG), check CO/CO₂ instead. In service mode the boiler runs both the heating and hot water circuits (MI 6.5). Table 5 gives a central heating max. rated heat input of 24.34 kW for both sizes (hot water: 25.5 and 30.61 kW). |
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Flue integrity More infoHide infoAt the air intake sample point on the flue turret, boiler case on, boiler running at maximum output, readings allowed to stabilise (MI 7.2). Readings outside these limits mean a problem with the flue system or combustion circuit, e.g. missing or dislodged seals. | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 6 720 813 278 (2015/07)
Enter service mode for high and low rate
High rate
- Hold eco and spanner/return together for at least 5 seconds.
- Chimney sweep symbol shows at the top and Max flashes at the bottom. It goes to maximum by itself.
Low rate
- Press ▼ for minimum. Min flashes at the bottom left of the display.
- Press ▲ to go back to maximum. Max flashes.
Ending the test
- Press ok to come out (MI 6.5). The MI differs: section 7.6 says press spanner/return instead.
- It ends by itself after 15 minutes.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| 25Si Compact ErP | 47-406-73 | NG |
| 30Si Compact ErP | 47-406-75 | NG |
| 25Si Compact ErP LPG | 47-406-74 | LPG |
| 30Si Compact ErP LPG | 47-406-76 | LPG |
Source: Greenstar Si Compact ErP wall hung RSF gas fired condensing combination boiler installation, commissioning and servicing instructions, 6 720 813 278 (2015/07).
Sections: Cover (GC numbers); 3.3 Technical data; 6.5 Commissioning; 6.5.1 Checking the gas inlet pressure; 6.5.2 Checking the gas rate; 6.5.3 Gas rating test; 6.7 CO and combustion checks; 7.2 Checking flue integrity; 7.4 Checking the gas inlet pressure; 7.5.1 Setting the boiler to maximum; 7.6 Flue gas analysis.
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.