Worcester Bosch Greenstar 8000 Style system (GR8700iW 30 S, 35 S and SB)
System boiler, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoFrom Tables 22 and 23 (MI 8.7 and 8.10), boiler at maximum in chimney sweep mode. CO₂ should be measured 10 minutes after firing, with the combustion chamber cover on (MI 8.10). The technical data (MI 12.1) gives the same figures without a tolerance, for both sizes. SB models have a black front panel and share the figures. | 9.5% ± 0.4 | 10.8% ± 0.4 |
CO₂ at low rate More infoHide infoFrom Tables 22 and 23, boiler at minimum in chimney sweep mode, cover on, 10 minutes after firing. The technical data gives the same figures without a tolerance, for both sizes. | 8.6% ± 0.4 | 10.2% ± 0.4 |
Maximum CO More infoHide infoThe MI gives two limits. Tables 22 and 23 give <250ppm at maximum and <75ppm at minimum, and MI 8.10.1 says the CO content must be < 250 ppm. The commissioning checks flow chart (MI 6.9, Fig. 67) uses CO < 350ppm at both maximum and minimum rate. The MI doesn’t say which takes priority. |
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CO/CO₂ ratio More infoHide infoFrom the commissioning checks flow chart (MI 6.9, Fig. 67), at maximum and minimum rate. MI 6.7 says to refer to the technical data for CO/CO₂ ratios, but the technical data doesn’t give any. | < 0.004 | < 0.004 |
O₂ at high rate More infoHide infoFrom Tables 22 and 23. No tolerance given. MI 8.10.1 says to check the CO₂ or O₂ content at maximum rated output against Table 23. | 4.0% | 4.6% |
O₂ at low rate More infoHide infoFrom Tables 22 and 23. No tolerance given. | 5.5% | 5.5% |
Working inlet pressure More infoHide infoFrom Table 16 and Figs. 65 and 66 (MI 6.6), boiler at maximum in chimney sweep mode. At the meter: NG 19–23 mbar. At the LPG storage/supply: 32–45 mbar. The drop from the meter or LPG supply to the gas valve must be no more than 2.5 mbar (NG) or 4 mbar (LPG). Table 16 gives a 2.5 mbar LPG pipework drop where Fig. 66 shows 2.0 mbar. |
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Gas rate at maximum More infoHide infoGas flow maximum rate, 10 minutes from lighting (MI 12.1, Table 26), for S and SB models. Measure at the gas meter after at least 10 minutes at maximum in chimney sweep mode, with all other gas appliances off (MI 6.7). Where there’s no gas meter (e.g. LPG), check CO/CO₂ instead. |
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Flue integrity More infoHide infoAt the air inlet sample point on the flue turret/adaptor, casing on, boiler at maximum in chimney sweep mode, readings allowed to stabilise (MI 6.10). Readings outside these limits mean a problem with the flue system or combustion circuit. | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 6720883855 (2019/01)
Enter service mode for high and low rate
High rate
- Hold ok for 5 seconds. When the countdown finishes and Chimney sweep shows, press ok.
- Confirm the query with Yes.
- Use ▲ to set maximum rated output. It’s accepted after 2 seconds and marked with a tick.
Low rate
- Use ▼ to set minimum rated output. It’s accepted after 2 seconds and marked with a tick.
Ending the test
- Press ok or ↩ to come out. It also returns to normal operation by itself after 30 minutes.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| GR8700iW 30 S NG | 41-406-87 | NG |
| GR8700iW 35 S NG | 41-406-86 | NG |
| GR8700iW 30 SB NG | 41-406-83 | NG |
| GR8700iW 35 SB NG | 41-406-82 | NG |
| GR8700iW 30 S LPG | 41-406-89 | LPG |
| GR8700iW 35 S LPG | 41-406-88 | LPG |
| GR8700iW 30 SB LPG | 41-406-85 | LPG |
| GR8700iW 35 SB LPG | 41-406-84 | LPG |
Source: Greenstar 8000 Style GR8700iW S gas fired condensing system boiler installation and maintenance instructions, 6720883855 (2019/01).
Sections: 3.5 Appliance type overview; 6.4 Chimney sweep mode; 6.6 Checking gas inlet pressure; 6.7 Checking the gas rate; 6.9 CO and combustion check; 6.10 Checking flue integrity; 6.11 Flue gas analysis; 8.7 Flue gas analysis; 8.10 Setting the air/gas ratio; 12.1 Technical data.
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.