Vaillant ecoTEC exclusive combi (835, 843)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoThe MI gives no CO₂ figures. It says to measure the CO/CO₂ content at maximum load (check programme P.01) once calibration has finished (status S.04, or S.14 in hot water mode), with the front casing on and closed and the flue fully installed, and not during calibration (status S.93). It also says that, as the boiler monitors combustion continuously, you don’t need to check the combustion. | Not given in MI | Not given in MI |
CO₂ at low rate More infoHide infoThe MI says to measure the CO/CO₂ content at minimum load (check programme P.02) once calibration has finished. | Not given in MI | Not given in MI |
Maximum CO More infoHide infoFrom the Benchmark CO and combustion ratio flowchart (MI appendix G). It gives less than 350 ppm for the checks at maximum and minimum rate, but less than 335 ppm in the box for re-checking after you’ve checked the seals around the burner, flue, door and case. The MI doesn’t explain the difference. |
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CO/CO₂ ratio More infoHide infoAt maximum and minimum rate (Benchmark flowchart, MI appendix G). | Less than 0.004 | Less than 0.004 |
O₂ | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoGas flow pressure at the measuring nipple on the gas valve, with the boiler at full load (check programme P.01). LPG figure is for G31. The technical data gives the gas connection pressure as 20.0 mbar for G20 natural gas and 37.0 mbar for G31 propane. Diagnostics code D.087 (gas type) has settings for Propane 50 mbar and Propane 30/37 mbar, but the MI gives no separate range for 50 mbar propane. |
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Gas rate at maximum More infoHide infoTechnical data figures at 15 °C and 1013 mbar, based on hot water generation. MI 7.14.2 says to check the rate at the gas meter with the front casing on, check programme P.01 running for at least 5 minutes and other gas appliances off. The gas rate table in 7.14.2 lists data plate Qnw values from 15.3 to 35.7 only, none matching these boilers’ maximum heat inputs in the technical data (heating 24.8 and 33.7 kW, hot water 32.7 and 40.2 kW), so it isn’t shown here. |
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Flue integrity More infoHide infoAt the air inlet test point, boiler at maximum rate (Benchmark flowchart, MI appendix G). MI 9.1 gives these readings at the air test point as signs of flue gas recirculation: O₂ in the intake air below 20 vol.%, or CO in the intake air of 100 ppm or more. | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 0020193968_03 (20.10.2017)
Enter service mode for high and low rate
High rate
Low rate
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| 835 (VUW 356/5-7 (H-GB)) | 47-044-66 | NG |
| 843 (VUW 436/5-7 (H-GB)) | 47-044-67 | NG |
Source: Installation and maintenance instructions ecoTEC exclusive, 0020193968_03 (20.10.2017).
Sections: 2.3 Validity of the instructions; 5.1.1 Information on liquefied petroleum gas operation; 7.6 Using check programmes; 7.14.1 Checking the leak-tightness of the flue gas installation and flue gas recirculation; 7.14.2 Checking the gas flow rate; 7.14.3 Checking the gas flow pressure; 7.14.4 Calibrating the heat generator and measuring the CO/CO₂ content and gas flow in heating mode; 7.14.4.1 Calibrating the heat generator and measuring the CO/CO₂ content and gas flow in domestic hot water mode; 9.1 Comfort protection mode for the heat cell; Appendix B Overview of diagnostics codes (D.087); Appendix G Commissioning Checklist (CO and combustion ratio flowchart); Appendix J Technical data.
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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.