Vaillant ecoTEC plus combi (VUW CS/1-5: 826, 832, 836, 840)
Combi, natural gas and LPG (840 natural gas only)
Not in the database yet:
- O₂ at high rate: MI gives diagrams only, no figures (MI section 9.13.4)
- O₂ at low rate: MI gives diagrams only, no figures (MI section 9.13.4)
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoThe MI says CO₂ no longer needs checking: combustion is checked by O₂ to BS 7967. It still asks for all combustion readings to be recorded in the Benchmark checklist. | Not given in MI | Not given in MI |
CO₂ at low rate | Not given in MI | Not given in MI |
Maximum CO More infoHide infoUndiluted, at maximum and minimum rate (Appendix B and the commissioning flow chart, Appendix N). The flow chart’s re-check, after checking the seals, says less than 335 ppm instead: possibly a misprint. Appendix B also says the country-specific maximum CO is higher, so check the country-specific regulations first. | Less than 350 ppm | Less than 350 ppm |
CO/CO₂ ratio More infoHide infoAt maximum and minimum rate (commissioning flow chart, Appendix N). | Less than 0.004 | Less than 0.004 |
O₂ at high rate More infoHide infoThe MI gives O₂ only as diagrams of the permissible maximum and minimum O₂ against heat input (one diagram per group of sizes), with no printed figures. Measured at the flue gas analysis point in chimney sweep mode at Max. DHW heat input (standard selection), front casing on, once calibration (S.093) has finished. VUW 30/40 (840) has natural gas curves only. | Not added yet – see MI 9.13.4 | Not added yet – see MI 9.13.4 |
O₂ at low rate More infoHide infoSame diagrams (MI 9.13.4), which cover the whole heat input range. The MI’s O₂ check itself is done at Max. DHW heat input. | Not added yet – see MI 9.13.4 | Not added yet – see MI 9.13.4 |
Working inlet pressure More infoHide infoPermissible gas flow pressure for Great Britain, measured at the gas valve test nipple with the boiler at maximum power in chimney sweep mode (the MI also mentions the test nipple on the gas isolation valve). Nominal gas connection pressure (technical data): NG 20.0 mbar, LPG 37.0 mbar. MI 7.1.1 says to assume a maximum permissible operating pressure of 18 mbar at the product’s gas inlet (allowing 1 mbar pipe loss), which doesn’t match the 13.0–23.0 mbar range. |
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Gas rate at maximum More infoHide infoGas flow rate for max. gas volume at 15 °C and 1013 mbar (technical data). VUW 30/40 (840) is natural gas only (gas category I2H, and not in the MI’s list of products that can be converted to LPG). MI 9.13.5 also checks the gas rate at the meter (front casing on, check programme P.01, after at least 5 minutes) against a table by the Qnw on the data plate, nominal +5%/–10%; that table’s Qnw values don’t all match the DHW heat inputs in the technical data. |
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Flue integrity More infoHide infoAt the air inlet test point with the boiler at maximum rate (commissioning flow chart, Appendix N). MI 9.13.2: in chimney sweep mode with the front casing closed, use the air analysis point to check extended flue installations for recirculation. | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 0020308118_05 (31.05.2023)
Enter service mode for high and low rate
High rate
Steps not added yet. Follow the MI.
Low rate
Steps not added yet. Follow the MI.
Ending the test: follow the MI.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| VUW 20/26CS/1-5 (N-GB) ecoTEC plus 826 | 47-044-92 | NG |
| VUW 25/32CS/1-5 (N-GB) ecoTEC plus 832 | 47-044-93 | NG |
| VUW 30/36CS/1-5 (N-GB) ecoTEC plus 836 | 47-044-94 | NG |
| VUW 30/40CS/1-5 (N-GB) ecoTEC plus 840 | 47-044-95 | NG |
Source: ecoTEC plus VU../VUW.. installation and maintenance instructions, 0020308118_05 (31.05.2023).
Sections: 3 Technical data; 4 Notes on the documentation (Gas Council Numbers); 7.1.1 Gas supply; 8.9 Running the chimney sweep mode (combustion analysis); 9.13.2 Checking the air/flue pipe/flue gas recirculation; 9.13.3 Checking the gas connection pressure/gas flow pressure; 9.13.4 Checking the O2 content; 9.13.5 Checking the gas flow rate; Appendix B Inspection and maintenance work; Appendix N Commissioning Flow Chart.
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.