Vaillant ecoFIT pure 412 - 435 heat only (VU 126, 156, 186, 256, 306, 356/6-3 OV)
Heat only (open vent), natural gas
Combustion figures
| Figure | Natural gas (G20) |
|---|---|
CO₂ at high rate More infoHide infoThe MI gives two tolerances. Check (MI 7.8.3 at commissioning and 11.4 at service): check programme P.01 (maximum load), wait 5 minutes for a stable reading, measure at the flue gas analysis point; the table applies with the front casing removed or installed. If it’s out at commissioning, don’t start the boiler and contact Vaillant; if it’s out at service, set it as in MI 11.5. Setting (MI 11.5): CO₂ at full load, the value to set when the CO₂ has to be adjusted. The text says this is the value with the front casing removed, but the table heading says removed/installed front casing. |
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CO₂ at low rate | Not given in MI |
Maximum CO More infoHide infoThe setting table (MI 11.5) gives CO at full load. The Benchmark flue gas analysis flowchart in the appendix (MI p. 38) gives less than 350 ppm at maximum and minimum rate, and one recheck box on it prints 335 ppm instead. The MI doesn’t say which limit takes priority. |
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CO/CO₂ ratio More infoHide infoThe setting table (MI 11.5) gives the ratio with no rate in the row (the table’s other rows are at full load). The Benchmark flue gas analysis flowchart in the appendix (MI p. 38) gives less than 0.004 at maximum and minimum rate. The MI doesn’t say which limit takes priority. |
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O₂ at high rate More infoHide infoMI 11.5 setting table, O₂ at full load, printed as 4.5 ±1.8 vol. %. | 4.5% ± 1.8 |
O₂ at low rate | Not given in MI |
Working inlet pressure More infoHide infoPrinted as 1.7–2.5 kPa (17.0–25.0 mbar), Great Britain, natural gas G20. Measured at the reference test point (the measuring nipple on the gas isolator cock) with the boiler at full load, all other gas appliances working. MI 7.8.1 says to use check programme P.01 (system with eBUS controller) or P.03 (without), but P.03 isn’t in the check programme list in MI 6.5. Nominal G20 supply pressure in the technical data: 2.0 kPa (20.0 mbar). |
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Gas rate at maximum More infoHide infoTechnical data (MI appendix I): gas flow at P max. in hot water mode (G20). In heating mode the technical data gives VU 126/6-3 1.3, VU 156/6-3 1.6, VU 186/6-3 1.9, VU 256/6-3 2.7, VU 306/6-3 3.2 and VU 356/6-3 3.8 m³/h. The MI 7.7 check (front casing on, check programme P.01, wait at least 5 minutes, all other gas appliances off, measure at the gas meter) uses a table by Qnw on the data plate, nominal (+5% / −10%): 15.3 kW 1.62 (1.70 / 1.46); 18.4 kW 1.95 (2.05 / 1.76); 24.7 kW 2.61 (2.74 / 2.35); 25.7 kW 2.72 (2.86 / 2.45); 28.6 kW 3.03 (3.18 / 2.73); 30.6 kW 3.24 (3.40 / 2.92); 35.7 kW 3.78 (3.97 / 3.40) m³/h. The technical data gives Qnw (maximum heat input, hot water) as 15.3, 18.4, 25.7, 30.6, 35.7 and 35.7 kW for the six models in order, so the 24.7 and 28.6 kW rows match none of them. |
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Flue integrity More infoHide infoBenchmark flue gas analysis flowchart in the appendix (MI p. 38): analyser probe in the air inlet test point, boiler at maximum rate. MI 7.8.2 says to check for flue gas recirculation using the air analysis point on extended flue installations. | O₂ ≥ 20.6% CO₂ < 0.2% |
From 0020230535_01 (25.10.2016)
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 |
|---|---|---|
| VU 126/6-3 OV (H-GB) | 41-694-08 | NG |
| VU 156/6-3 OV (H-GB) | 41-694-09 | NG |
| VU 186/6-3 OV (H-GB) | 41-694-10 | NG |
| VU 256/6-3 OV (H-GB) | 41-694-11 | NG |
| VU 306/6-3 OV (H-GB) | 41-694-12 | NG |
| VU 356/6-3 OV (H-GB) | 41-694-19 | NG |
Source: Vaillant ecoFIT pure 412 - 435 installation and maintenance instructions, 0020230535_01 (25.10.2016).
Sections: 2.3 Validity of the instructions; 6.5 Using check programmes; 7.2 Checking the factory setting; 7.7 Checking the gas flow rate; 7.8.1 Checking the gas connection pressure; 7.8.2 Checking the leak-tightness of the flue gas installation and flue gas recirculation; 7.8.3 Checking the CO₂ content; 11.4 Checking the CO₂ content; 11.5 Setting the CO₂ content; Appendix H Commissioning Checklist (flue gas analysis flowchart); Appendix I 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.