Vaillant ecoFIT pure 825–835 combi (VUW 256/6-3, 306/6-3, 356/6-3)
Combi, natural gas
Combustion figures
| Figure | Natural gas (G20) |
|---|---|
CO₂ at high rate More infoHide infoMeasured at the flue gas analysis point in check programme P.01 (maximum load), after waiting 5 minutes for a stable reading. Both figures apply with the front casing removed or fitted. The check figure is in MI 7.11.4 and 11.4; the setting figure is from the CO₂ setting table in MI 11.5 (CO₂ at full load), set with the front casing removed. At commissioning (MI 7.11.4) a reading outside the check figure means don’t start the boiler and contact Vaillant; at service (MI 11.4) set the CO₂ as in MI 11.5. |
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CO₂ at low rate | Not given in MI |
Maximum CO More infoHide infoFrom the CO₂ setting table in MI 11.5. The Benchmark flow chart in the appendix (MI p. 44) uses CO less than 350 ppm at maximum and minimum rate as its pass level, and less than 335 ppm in the box after rechecking the seals. |
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CO/CO₂ ratio More infoHide infoFrom the CO₂ setting table in MI 11.5. The Benchmark flow chart in the appendix (MI p. 44) uses a ratio less than 0.004 at maximum and minimum rate. |
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O₂ at high rate More infoHide infoAt full load, from the CO₂ setting table in MI 11.5 (given as vol. %). | 4.5% ± 1.8 |
O₂ at low rate | Not given in MI |
Working inlet pressure More infoHide infoAt the measuring nipple on the gas isolator cock, with the boiler at full load in check programme P.01 (or P.03 without an eBUS controller) and all other gas appliances in the property working. The MI gives 1.7–2 kPa (17.0–20 mbar). The technical data gives a G20 gas supply pressure of 2.0 kPa (20.0 mbar). |
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Gas rate at maximum More infoHide infoTechnical data, gas flow at P max. in hot water mode (G20). At P max. in heating mode: 1.9, 2.7 and 2.7 m³/h. The gas rate check in MI 7.10 is done at the gas meter in check programme P.01, front casing fitted, after at least 5 minutes, with all other gas appliances off, against a table by Qnw from the data plate: 25.7 kW: 2.72 m³/h (2.45–2.86); 30.6 kW: 3.24 m³/h (2.92–3.40); 35.7 kW: 3.78 m³/h (3.40–3.97). These Qnw figures are the maximum hot water heat inputs of the VUW 256/6-3, 306/6-3 and 356/6-3 in the technical data. |
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Flue integrity More infoHide infoAt the air intake test point (supply air measuring stub), boiler at maximum rate. From the Benchmark flow chart in the appendix (MI p. 44). MI 7.11.2 says to check extended flues for flue gas recirculation at the air analysis point. | O₂ ≥ 20.6% CO₂ < 0.2% |
From 0020230531_01 (25.10.2016)
Enter service mode for high and low rate
High rate
Low rate
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| VUW 256/6-3 (H-GB) | 47-044-68 | NG |
| VUW 306/6-3 (H-GB) | 47-044-74 | NG |
| VUW 356/6-3 (H-GB) | 47-044-70 | NG |
Source: Vaillant ecoFIT pure 825 - 835 installation and maintenance instructions, 0020230531_01 (25.10.2016).
Sections: 2.3 Validity of the instructions; 6.5 Using check programmes; 7.3 Checking the factory setting; 7.10 Checking the gas flow rate; 7.11.1 Checking the gas connection pressure (gas flow pressure); 7.11.2 Checking the leak-tightness of the flue gas installation and flue gas recirculation; 7.11.4 Checking the CO₂ content; 11.4 Checking the CO₂ content; 11.5 Setting the CO₂ content; H Commissioning Checklist (CO and combustion ratio flow chart); I 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.