Worcester Bosch Greenstar HE plus combi (ZWBR 7-30 HE plus, ZWBR 11-35 HE plus, ZWBR 11-30 LPG, ZWBR 14-35 LPG)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoFrom Table 15 (ZWBR 7-30) and Table 16 (ZWBR 11-35) in MI 8.1, CO₂ reading at max. rated heat output. MI 8.1 measures it with an electronic tester at the flue gas testing point (234, Fig. 40), probe inserted about 135 mm, with service function 2.0 Operating mode set to Max; in MI 8.1 the outer case is removed before the boiler is switched on for this check. No tolerance is given anywhere in the MI. Size 30 is the ZWBR 7-30 (NG) and ZWBR 11-30 (LPG); size 35 is the ZWBR 11-35 (NG) and ZWBR 14-35 (LPG), as in Table 2. Tables 15 and 16 are headed with the NG model codes only but include the LPG rows. The technical data (MI 1.9, Table 2, CO₂ level at max. rated heat output) gives the same NG figures and the same LPG figure for the 30 size. The manual contradicts itself for the LPG 35 size: Table 2 gives 10.8% for the ZWBR 14-35 Propane, but Table 16 gives 11.0% for LPG G31 (propane) under its ZWBR 11-35 heading. The MI doesn’t say which is right. MI 8.2.2 (Testing CO and CO₂) measures at the same testing point in chimney sweep mode, which runs the boiler at max. rated heat output or the set heating output for 15 minutes, but gives no figures of its own. The MI says the operational CO₂ level is set at the factory and no adjustment is necessary when installing a natural gas fired appliance (MI 5.1), that the appliance is set at the factory and adjustment is not necessary (MI 7.3), that the setting is factory sealed at maximum (MI 8), and that combustion performance must be checked before and after any servicing work on the combustion and burner components (MI 9.2). | 9.2% |
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CO₂ at low rate More infoHide infoFrom Tables 15 and 16 (MI 8.1), CO₂ reading at min. rated heat output, with service function 2.0 Operating mode set to Min. Table 16 (ZWBR 11-35) gives one figure for both max. and min. rated heat output. The technical data (MI 1.9, Table 2, CO₂ level at min. rated heat output) gives the same NG figures and the same LPG figure for the 30 size; for the LPG 35 size Table 2 gives 10.8% (ZWBR 14-35 Propane) and Table 16 gives 11.0%. The MI 8.1 step for setting the minimum (gas valve adjusting screw 64, Fig. 42) refers only to Table 15, even though Table 16 covers the ZWBR 11-35. MI 8.1 says to recheck the levels at min. and max. rated heat output after adjusting. |
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Maximum CO More infoHide infoMI 8.2.2 (Testing CO and CO₂) says to measure the CO and CO₂ levels at the flue gas testing point (234) in chimney sweep mode, but the MI gives no CO limit or CO/CO₂ ratio anywhere. | Not given in MI | Not given in MI |
CO/CO₂ ratio | Not given in MI | Not given in MI |
O₂ More infoHide infoThe MI gives O₂ only for the combustion air check (see Flue integrity, MI 8.2.1). | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoMI 5.1 and MI 8 (Checking the gas supply pressure) say to check the gas supply pressure at the gas supply pressure testing point (Fig. 2, item 7). The function diagram (MI 1.7, Fig. 3) shows item 7 on the inlet of the gas valve. The MI words the figures as limits: natural gas appliances must not be operated if the gas supply pressure is below 18 mbar or above 24 mbar; LPG appliances must not be operated if the supply pressure is not 37 mbar at the inlet to the appliance (MI 5.1), or is below or above 37 mbar (MI 8). No tolerance is given for LPG. The MI doesn’t say whether the boiler should be running during the check. The technical data (MI 1.9, Table 2) gives a gas supply pressure of 20 mbar (NG G20) and 37 mbar (LPG) without saying where it’s measured, and MI 8 says G20 appliances are factory set to Wobbe index 15 kWh/m³ and 20 mbar supply pressure. |
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Gas rate at maximum More infoHide infoFrom the technical data (MI 1.9, Table 2), maximum gas flow rate after 10 minutes from lighting; NG for G20 (CVnet 34.02 MJ/m³), LPG for CVnet 88 MJ/m³. Table 2 gives a max. rated heat input net of 29.5 kW (30 size) and 35.5 kW (35 size). The NG heating/hot water output settings tables give a gas volume flow rate at display code 100 of 51.6 l/min (ZWBR 7-30, MI 10.3, Table 20) and 62.1 l/min (ZWBR 11-35, MI 10.5, Table 22), at a flow/return temperature of 80/60 degrees C. The LPG tables (MI 10.4, Table 21 and MI 10.6, Table 23) give no gas rate. MI 7.2.4 says to measure the gas flow rate after setting the heating output (service function 5.0) and compare it with the figures for the code number shown. |
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Flue integrity More infoHide infoFrom MI 8.2.1 (Testing the O₂ or CO₂ level in the combustion air): the O₂ level must not be less than 20.6% and the CO₂ level must not exceed 0.2% (printed with decimal commas, 20,6 % and 0,2 %). Measured at the combustion air testing point (234.1, Fig. 43), probe inserted about 80 mm, in chimney sweep mode, which runs the boiler at max. rated heat output or the set heating output and gives 15 minutes to measure. The MI says this checks the gas tightness of a type C13 or C33 flue system. It doesn’t say whether the case should be on or off. | O₂ ≥ 20.6% CO₂ ≤ 0.2% | O₂ ≥ 20.6% CO₂ ≤ 0.2% |
From 6 720 610 597 GB (03.02)
Enter service mode for high and low rate
High rate
- On the text display, go to Settings, Service, Display service parameters with ▼/▲ and ▶.
- Hold ▶ for about 5 seconds until Adjust service parameters shows.
- Press ▼/▲ to 2.0 Operating mode normal, press ▶, then ▼/▲ to select Max.
- Or: hold the Chimney sweep button until the display shows - -. It runs at maximum or the set heating output.
Low rate
- Press ▼ or ▲ to select Min.
Ending the test
- Press ▼/▲ to normal, press ▶, press ▼ to select yes at Store settings, then press ▶.
- Chimney sweep: hold the button until - - shows. It also ends by itself after 15 minutes.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| ZWBR 7-30 HE plus | 47-311-75 | NG |
| ZWBR 11-35 HE plus | 47-311-57 | NG |
| ZWBR 11-30 LPG | Not added yet | LPG |
| ZWBR 14-35 LPG | Not added yet | LPG |
Source: Worcester Greenstar HE plus combi wall mounted condensing boiler for central heating and mains fed domestic hot water installation and servicing instructions, 6 720 610 597 GB (03.02).
Sections: Cover (GC numbers); 1.6 Layout of appliance (Fig. 2); 1.7 Function (Fig. 3); 1.9 Technical data (Table 2); 5.1 Commissioning; 7.2.1 General description (Setting service functions); 7.2.4 Setting the heating output; 7.3 Setting the gas/air ratio; 8 Converting the appliance to different gas types (Checking the gas supply pressure, Table 14); 8.1 Setting the gas/air ratio (Tables 15 and 16); 8.2.1 Testing the O₂ or CO₂ level in the combustion air; 8.2.2 Testing CO and CO₂; 9.2 Description of servicing operations; 10.3 to 10.6 Heating/hot water output settings (Tables 20 to 23).
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.