Vaillant ecoTEC plus VUW combi (824, 831, 837)
Combi, natural gas and LPG
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoTable 12.1 (Factory gas setting): after 5 minutes at full load (test program P.01), at the flue gas analysis point. The MI’s check (12.1.3) has the front casing removed, and when adjusting you set the case-off figure (MI 12.1.4). The MI says combustion is factory set and no combustion measurement is needed to set up the boiler (MI 10.11.1); check or adjust CO₂ after replacing the gas valve, after a gas conversion, or if incorrect combustion is suspected (MI 12.1.3). |
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CO₂ at low rate | Not given in MI | Not given in MI |
Maximum CO More infoHide infoThe MI disagrees with itself. Its own table 12.1 gives < 250 ppm at full load. The Benchmark flowchart at the back of the MI (PDF p. 85) gives < 350 ppm at maximum and minimum rate, and < 335 ppm in its re-check box after the seals have been checked. The MI doesn’t say which to use. |
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CO/CO₂ ratio More infoHide infoThe MI disagrees with itself. Table 12.1 gives the ratio without stating the rate. The Benchmark flowchart at the back of the MI (PDF p. 85) gives < 0.004 at maximum and minimum rate. The MI doesn’t say which to use. |
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O₂ | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoTable 10.3: minimum and maximum at the reference test point (the lower measuring nipple on the gas valve), boiler at full load (test program P.01, or hot taps fully open), front casing off. The MI gives NG 1.3–2.3 kPa (13–23 mbar) and LPG 2.3–4.3 kPa (23–43 mbar). Technical data (table 17.2) gives the gas connection pressure as 20 mbar NG and 37 mbar LPG, without saying where it’s measured. |
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Gas rate at maximum More infoHide infoTable 10.2 (as per BS EN 483): nominal rate, with the MI’s −10% and +5% limits in brackets. Measure at the gas meter with the front casing on, at least 5 minutes into test program P.01 (or with the hot taps fully open), with all other gas appliances off. Table 10.2 lists rates by nominal output, not model: these are its last three rows (24, 31 and 37 kW), which match the VUW technical data (table 17.2, rounded there). The 37 kW system boiler row above them is different (4.03 m³/h). |
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Flue integrity More infoHide infoFrom the Benchmark flowchart (PDF p. 85): at the air inlet test point, boiler at maximum rate. MI 10.11.2 says to check at the air measure point with the analyser and, if you find any CO or CO₂ in the fresh air, look for a flue gas leak or recirculation; it strongly recommends this check where the flue is longer than 2 m. | O₂ ≥ 20.6% CO₂ < 0.2% | O₂ ≥ 20.6% CO₂ < 0.2% |
From 0020116700_06 GBIE 012014
Enter service mode for high and low rate
High rate
Low rate
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| ecoTEC plus 824 (VUW GB 246/5-5) | 47-044-40 | NG |
| ecoTEC plus 831 (VUW GB 316/5-5) | 47-044-41 | NG |
| ecoTEC plus 831 (VUW GB 316/5-5) LPG | 47-044-46 | LPG |
| ecoTEC plus 837 (VUW GB 376/5-5) | 47-044-42 | NG |
Source: Vaillant ecoTEC plus VU, VUW installation and maintenance instructions, 0020116700_06 GBIE 012014.
Sections: 1.3 Applicability of the instructions; 1.7 Type overview; 3 Description of the appliance; 10.4 Using test programs; 10.11 Checking the gas setting; 10.11.2 Checking for tightness of the flue gas installation and flue gas recirculation; 10.11.3 Checking the gas flow rate; 10.11.4 Checking the gas inlet working pressure; 12.1.3 Checking the CO/CO₂ ratio and the CO₂ concentration; 12.1.4 Adjusting the CO₂ concentration (or the air ratio); 17 Technical data; Benchmark CO and combustion ratio flowchart (PDF p. 85).
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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.