Worcester Bosch Checked against MI

Worcester Bosch Greenstar 8000 Style combi (GR8700iW 30 C, 35 C, 40 C, 45 C, 50 C and CB)

Combi, natural gas and LPG

Combustion figures

Figure	Natural gas (G20)	LPG (G31)
CO₂ at high rate More infoHide info From 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 every size. CB models have a black front panel and share the figures.	9.5% ± 0.4	10.8% ± 0.4
CO₂ at low rate More infoHide info From 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 every size.	8.6% ± 0.4	10.2% ± 0.4
Maximum CO More infoHide info The 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.	Max rate <250ppm Min rate <75ppm Flow chart < 350ppm	Max rate <250ppm Min rate <75ppm Flow chart < 350ppm
CO/CO₂ ratio More infoHide info From 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 info From Tables 22 and 23. No tolerance given.	4.0%	4.6%
O₂ at low rate More infoHide info From Tables 22 and 23. No tolerance given. MI 8.10.1 says to set the CO₂ or O₂ content at minimum rated output.	5.5%	5.5%
Working inlet pressure More infoHide info From 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 MI splits the gas valve figure at 40 kW without saying which models that covers. The MI text says the drop from the meter or LPG supply to the gas valve must be no more than 2.5 mbar (NG ≤ 40 kW), 3.5 mbar (NG > 40 kW) or 4 mbar (LPG), but Table 16 allows up to 5 mbar for LPG > 40 kW. Table 16 gives a 2.5 mbar LPG pipework drop where Fig. 66 shows 2.0 mbar.	Appliance inlet 18–22 mbar Gas valve test point 16.5–20.5 mbar (≤ 40 kW), 15.5–19.5 mbar (> 40 kW)	Appliance inlet 29.5–42.5 mbar Gas valve test point 28–41 mbar (≤ 40 kW), 27–40 mbar (> 40 kW)
Gas rate at maximum More infoHide info Gas flow maximum rate, 10 minutes from lighting (MI 12.1, Tables 26–28), for C and CB 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). Running a hot water tap doesn’t guarantee maximum output. Where there’s no gas meter (e.g. LPG), check CO/CO₂ instead.	30 3.2 m³/h 35 3.6 m³/h 40 4.3 m³/h 45 4.6 m³/h 50 5.1 m³/h	30 2.3 kg/h 35 2.7 kg/h 40 3.2 kg/h 45 3.4 kg/h 50 3.8 kg/h
Flue integrity More infoHide info At 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 6720883864 (2019/02)

Enter service mode for high and low rate

High rate

Hold ok for 5 seconds. Press ok when the countdown finishes and Chimney sweep shows.
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.
Use ▲ to go back to maximum.

Ending the test

Press ok or ↩ to come out. It also ends by itself after 30 minutes.

Models and GC numbers

Model	GC number	Gas
GR8700iW 30 C NG	47-800-03	NG
GR8700iW 35 C NG	47-800-02	NG
GR8700iW 40 C NG	47-800-01	NG
GR8700iW 45 C NG	47-406-99	NG
GR8700iW 50 C NG	47-406-98	NG
GR8700iW 30 CB NG	47-406-97	NG
GR8700iW 35 CB NG	47-406-96	NG
GR8700iW 40 CB NG	47-406-95	NG
GR8700iW 45 CB NG	47-406-94	NG
GR8700iW 50 CB NG	47-406-93	NG
GR8700iW 30 C LPG	47-800-13	LPG
GR8700iW 35 C LPG	47-800-12	LPG
GR8700iW 40 C LPG	47-800-11	LPG
GR8700iW 45 C LPG	47-800-10	LPG
GR8700iW 50 C LPG	47-800-09	LPG
GR8700iW 30 CB LPG	47-800-08	LPG
GR8700iW 35 CB LPG	47-800-07	LPG
GR8700iW 40 CB LPG	47-800-06	LPG
GR8700iW 45 CB LPG	47-800-05	LPG
GR8700iW 50 CB LPG	47-800-04	LPG

Source: Greenstar 8000 Style GR8700iW C gas fired condensing combi boiler installation and maintenance instructions, 6720883864 (2019/02).

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.