Vaillant EcoTEC Plus 831 Boiler Instruction Manual
Vaillant EcoTEC Plus 831 Boiler
Vaillant EcoTEC Plus 831 Boiler
Vaillant EcoTEC Plus 831 Instructions
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Vaillant EcoTEC Plus 831 Boiler Specifications
| Feature | Specification (ecoTEC plus 612) |
|---|---|
| Category | II2H3P |
| SEDBUK Band | A |
| SAP Seasonal Efficiency | 91.1 % |
| CH Heat Output Range (80°C/60°C Return) | 8.7 – 24.0 kW |
| CH Heat Output Range (60°C/40°C Return) | 9.0 – 24.7 kW |
| CH Heat Output Range (50°C/30°C Return) | 9.2 – 25.5 kW |
| CH Heat Output Range (40°C/30°C Return) | 9.4 – 26.0 kW |
| Maximum DHW Output | 31.0 kW |
| Maximum Output for Heating | 24 kW |
| Minimum Output | 8.7 kW |
| Inlet Gas Working Pressure Required (G20, Natural Gas) | 20 mbar |
| Inlet Gas Working Pressure Required (G31, Propane) | 37 mbar |
| Connected Load (G20, Natural Gas) | 3.3 m³/h |
| Connected Load (G31, Propane) | 2.46 kg/h |
| Exhaust Mass Rate (Min. Thermal Load 40°C/30°C) | 4.2 g/s |
| Exhaust Mass Rate (Max. Thermal Load 80°C/60°C) | 14.4 g/s |
| Exhaust Temperature (Min. Thermal Load 40°C/30°C) | 40 °C |
| Exhaust Temperature (Max. Thermal Load 80°C/60°C) | 83 °C |
| NOx Class | 5 |
| Protection Class | IP X4D |
| Maximum Flow Temperature | 85 °C |
| Adjustable Flow Temperature | 30 – 85 °C |
| Default Max. Flow Temperature Setting | 75 °C |
| Maximum CH System Pressure | 3.0 bar |
| Circulation Water Volume (ΔT=20K) | 1032 l/h |
| Approx. Condensation Volume (50°C/30°C Heating) | 2.2 l/h |
| Pump Delivery Height | 250 mbar |
| Minimum DHW Flow Rate | 1.5 l/min |
| DHW Flow Rate (ΔT=35K Rise) | 12.7 l/min |
| Approx. DHW Flow Rate (Factory Set ΔT=42K) | 10.6 l/min |
| Permitted DHW Overpressure | 10 bar |
| Mains Water Pressure Required (Max. Flow Rate) | 0.75 bar |
| Mains Water Pressure Required (Min. Flow Rate) | 0.15 bar |
| Hot Water Discharge Temperature Range | 35 – 65 °C |
| Exhaust Flue | 60/100 mm |
| Flue Categories | C13, C33, C43, C53, C83, B23, B33 |
| Expansion Vessel Pre-charge Pressure | 0.75 bar (10 L vessel) |
| Connections Heating Flow/Return | 22 mm |
| Gas Inlet Connection | 15 mm |
| Pressure Relief Discharge Pipework (Min.) | 15 mm |
| Condensate Drain (Min. Internal Drain) | 19 mm |
| Dimensions (H x W x D) | 720 x 440 x 335 mm |
| Weight (Boiler Only) | 38 kg |
| Primary Water Content | 2.3 l |
| Electrical Supply Voltage | 230/50 V ~/Hz |
| Internal Fuse (Slow) Main Voltage | 2 A |
| Power Input | 125 W |
Vaillant EcoTEC Plus 831 Boiler Details
The Vaillant EcoTEC Plus 831 is a sophisticated, wall-mounted condensing boiler engineered to provide both central heating and instantaneous domestic hot water efficiently. As a combination boiler, it delivers hot water directly without the need for a separate storage cylinder, simplifying installation and reducing associated pipework. Its compact design allows for flexible placement within a home.
This model features a user-friendly digital display system, providing real-time information on heating flow temperature, system pressure, and operational status. An intuitive control panel with ‘i’ (information), ‘+’, ‘-‘, and ‘Reset’ buttons allows homeowners to monitor and manage their heating system with ease, displaying error codes in the event of a fault for quick diagnosis.
A standout feature is the Warmstart function, unique to combination boilers like the EcoTEC Plus 831. This system pre-heats the domestic hot water heat exchanger to a user-selected temperature, ensuring hot water is available almost instantly when a tap is opened, enhancing user comfort and convenience. The hot water temperature can be easily adjusted between approximately 35°C and 65°C.
For central heating, the boiler automatically adjusts its output to meet demand, operating economically. Users can set the maximum radiator temperature to suit seasonal needs, from spring/autumn to cold winter conditions. The boiler also incorporates an anti-cycling economiser control, a smart feature that prevents energy-wasting short bursts of operation, optimising fuel efficiency and system longevity.
The EcoTEC Plus 831 includes an integral frost protection function, activating the boiler to heat the internal circuit to approximately 30°C if the temperature drops below 5°C. This critical safeguard helps prevent freezing within the boiler itself, though it's important to note that external system components may require additional protection. An automatic pump spin control also helps prevent pump seizure during periods of inactivity.
Designed for use with sealed central heating systems, this model comes fully assembled with a built-in circulating pump, expansion vessel, and diverter valve. It supports standard 100 mm or optional 125 mm flue systems, offering installation flexibility. The boiler’s siphonic condensate discharge system, with a 140 mm water trap, effectively collects and drains condensate, minimizing the risk of freezing in the drain pipe.
The product is available for Natural Gas and also as an LPG version, catering to a broader range of installations. Vaillant offers a two-year factory guarantee for ecoTEC plus appliances, contingent on an annual service by a competent installer for the second year. This commitment to reliability underscores the boiler’s high-quality engineering and design.
Frequently Asked Questions (FAQs)
Can't find the answer you need? Here are some frequently asked questions about the Vaillant EcoTEC Plus 831 Boiler, and we answer them below.










