Worcester Bosch Greenstar Si combi (25Si, 30Si)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoFrom the CO/CO₂ settings for Greenstar Si table in Setting the air/gas ratio (MI page 54 for the SIT 848.093 Sigma valve, page 55 for the Dungs GB-ND 055 DO1 S20 valve; the two tables are the same), boiler at maximum in service mode (30.2, 30.3). The tables say CO/CO₂ should be measured after 10 minutes. The flue gas test point is on the appliance flue elbow, under cap D. The MI doesn’t say whether the case should be on or off; 30.5 ends by re-assembling and refitting the boiler case. The technical data (MI page 6) gives the same figures without a tolerance, for both sizes, but says after 30 mins. The MI says the combustion is factory set and no adjustment is required if the gas inlet pressure is correct (MI Commissioning, page 35). After a service, the CO/CO₂ must be checked and set to the limits in Setting the air/gas ratio (MI Inspection and service, page 40). | 9.8% ± 0.5% | 11.0% ± 0.5% |
CO₂ at low rate More infoHide infoFrom the CO/CO₂ settings table (MI pages 54 and 55), central heating control set to minimum while in service mode (30.4, 30.5). The technical data (MI page 6) gives the same figures without a tolerance, for both sizes, after 30 mins. | 9.2% ± 0.5% | 10.5% ± 0.5% |
Maximum CO More infoHide infoFrom Setting the air/gas ratio (MI pages 54 and 55): printed under the CO/CO₂ settings table, and checked at maximum (30.3) and again at minimum (30.5). | less than 200ppm | less than 200ppm |
CO/CO₂ ratio More infoHide infoPrinted under the CO/CO₂ settings tables (MI pages 54 and 55) with the CO limit: CO - less than 200ppm (0.002 ratio). | 0.002 | 0.002 |
O₂ More infoHide infoThe MI gives no O₂ figures and no combustion air (flue integrity) test. | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoThe MI says to check the gas supply working pressure at the gas valve inlet point (inlet test nipple on the SIT or Dungs valve) is no less than N.G. 18.5 mbar, L.P.G. 37 mbar, with the boiler running at maximum in service mode and with all other gas appliances working (MI Commissioning, page 35). Setting the air/gas ratio (MI pages 54 and 55) says the inlet pressure, measured at the inlet pressure point on the gas valve with the boiler at maximum, should be no less than 18.5mb NG or 37mb for LPG. The general checks on the back cover (MI page 64) ask whether the incoming gas pressure is at least 18mbar with the boiler at maximum output, without saying where it’s measured or which gas; that’s lower than the 18.5 mbar natural gas minimum above. The MI gives no appliance inlet, meter or regulator figure (Gas supply, MI page 10). |
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Gas rate at maximum More infoHide infoGas flow rate, max. 10 minutes from lighting, natural gas figures for G20 (MI Technical data, page 6). Measure at the gas meter after 10 minutes operation at maximum (MI Commissioning, page 35). For LPG, where a gas meter is not available, the CO/CO₂ must be checked to the units shown in the setting of the air/gas ratio (MI page 35). The technical data gives a max. rated heat input of 25.51 kW (25Si) and 30.61 kW (30Si), and a central heating max. rated heat input of 24.62 kW for both sizes and both gases. |
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From 8 716 115 165a (06/2008)
Enter service mode for high and low rate
High rate
- Hold the service button for 10 seconds until it lights up. The blue power light flashes quickly.
- Turn the central heating control to maximum. Boiler goes to maximum and the blue light gives 5 pulses.
Low rate
- Turn the central heating control to minimum. Boiler goes to minimum and the blue light gives 2 pulses.
- Turn it back to maximum to return to maximum.
Ending the test
- Hold the service button for 2 seconds. It goes out and the blue power light stays on steady.
- Ends by itself after 15 minutes.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| Greenstar 25Si | 47-311-84 | NG |
| Greenstar 30Si | 47-311-85 | NG |
| Greenstar 25Si LPG | 47-311-88 | LPG |
| Greenstar 30Si LPG | 47-311-89 | LPG |
Source: Worcester Greenstar 25Si/30Si wall hung RSF gas fired condensing combination boiler instruction manual: installation, commissioning & servicing, 8 716 115 165a (06/2008).
Sections: Cover (GC numbers); Technical data (page 6); Gas supply (page 10); Commissioning (page 35); Inspection and service, Setting boiler to maximum (page 39) and CO/CO₂ after servicing (page 40); Setting the air/gas ratio, 30. Setting the CO/CO₂ (page 54 SIT valve, page 55 Dungs valve); General checks (back cover, page 64).
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.