Vaillant ecoTEC Plus 840 40kW Combi Boiler | 10036018 | Gas

Description

The Vaillant ecoTEC plus 840 (MPN 10036018, model VUW 30/40CS/1-5 (N-GB)) is a wall-hung condensing combination boiler and the highest-output model in the ecoTEC plus 826, 832, 836 and 840 series. It delivers instantaneous domestic hot water at 16.3 L/min with a 35 K temperature rise (19.0 L/min at 30 K to EN 13203-1) and a central heating output of 4.5 to 29.8 kW at 80/60 °C, making it a strong choice for properties with high simultaneous hot water demand.

Hand-built in Vaillant's Derbyshire plant, it is smart home ready through the myVAILLANT connect gateway and Vaillant eBUS controls, and uses IoniDETECT intelligent combustion monitoring with adaptive combustion regulation. It is a natural gas (G20) only, room-sealed (C13, C33, C43, C53) appliance with a 60/100 mm concentric flue connection, a 10 litre integral expansion vessel and a built-in installation assistant to speed up commissioning. Supplied as boiler only: the flue is ordered separately.

40.8 kW

Max. DHW heat input (Hi)

16.3 L/min

Hot water at 35 K rise

109.2%

Efficiency at 30% load (G20)

NOx 6

26.3 mg/kWh weighted

720×440×386

Height × width × depth (mm)

Up to 10 yrs

Guarantee via Vaillant Advance installer*

Safety and regulatory

Installation, commissioning and servicing must be carried out by a Gas Safe registered engineer in line with the manufacturer's instructions and BS 6891. The Benchmark Commissioning Checklist must be completed to validate the guarantee. Electrical work must comply with BS 7671; in a bathroom the boiler must be fitted in zone 2 or 3 only, with a fixed connection and a double pole isolator (contact gap of at least 3 mm).

Boiler only: flue not included

The air/flue system is not in the box. Order a Vaillant 60/100 mm (or 80/125 mm) concentric flue kit and any required terminal guard separately. Only original Vaillant air/flue components are system-certified for this boiler, and a terminal protection kit is required where the terminal is less than 2.0 m from the ground.

Natural gas only and sizing note

The ecoTEC plus 840 is category I2H (natural gas) and is not on the manufacturer's LPG conversion list. The 40 kW rating relates to hot water: the maximum heating output is 29.8 kW at 80/60 °C (32.3 kW at 50/30 °C). It is not approved for use with directly connected wall-hung hot water cylinders, multiple-flue configurations or cascades.

System preparation

Flush the heating system thoroughly and treat the water (target pH 8.2 to 10.0) before fitting. The manufacturer's commissioning checklist includes a system filter and mains water treatment for combi boilers. A manual filling device with double check valve is supplied.

Key features

Instant hot water, 40 kW class

Up to 19.0 L/min at 30 K rise and 16.3 L/min at 35 K rise, with a 2.0 L/min start-up flow rate, 35 to 65 °C hot water temperature range and a 14.0 L/min flow rate limiter. Requires only 0.7 bar mains pressure.

IoniDETECT combustion monitoring

Intelligent gas combustion monitoring with adaptive combustion regulation, so the gas-air ratio does not need adjusting within a gas family. Combustion is verified by an O₂ check in chimney sweep mode.

Smart home ready

Connects to the myVAILLANT connect gateway (VR 940f) through a dedicated interface for app control. Works with Vaillant eBUS controls, weather-compensated controls, the sensoROOM pure (VRT 50/2), and 230 V or 24 V third-party room thermostats.

Fast, guided commissioning

A built-in installation assistant walks the installer through filling, hydraulic mode, gas group and flue type. Check programmes, an actuator test and a 15 minute chimney sweep mode are included, alongside the Benchmark checklist.

Compact wall-hung design

720 × 440 × 386 mm with just 5 mm side clearance. Compartment ventilation is not required with a concentric flue. Supplied with 20 mm heating, 15 mm gas and 15 mm cold water connection pipes and a mounting template.

Built-in protection

Frost protection, overheating safety, a condensate blockage shut-off and a 10 litre expansion vessel are built in. Rated IPX5D with a stainless steel heat exchanger design (the "S" in the model code) and NOx Class 6 emissions.

Technical specification

Identification

Brand / range

Vaillant ecoTEC plus

Model

ecoTEC plus 840 (VUW 30/40CS/1-5 (N-GB))

MPN / article number

10036018 (article number 0010036018)

Gas Council number

47-044-95

Boiler type

Wall-hung condensing combination boiler

Fuel / gas category

Natural gas G20 at 20 mbar / I2H

Approved flue types

C13, C33, C43, C53 (room-sealed only)

CE / UKCA PIN

0063CU3910

Central heating performance (G20)

Heat output at 80/60 °C

4.5 to 29.8 kW

Heat output at 60/40 °C

4.8 to 31.2 kW

Heat output at 50/30 °C

5.0 to 32.3 kW

Heat output at 40/30 °C

5.2 to 32.9 kW

Heat input range (Hi)

4.8 to 30.6 kW

Efficiency at 30% load

109.2%

NOx emission / class

26.30 mg/kWh / Class 6

Flow temperature

30 to 80 °C adjustable (factory 75 °C), max. 85 °C

Max. operating pressure (heating)

2.5 bar

Circulation volume at 20 K, 80/60 °C

1,318 l/h

Remaining pump head

0.25 bar at nominal circulation

Condensate rate at 50/30 °C

Approx. 3.1 l/h (pH 3.5 to 4.0)

Domestic hot water

Max. DHW heat input

40.8 kW (Hi) / 45.3 kW (Hs)

Specific flow rate D (30 K, EN 13203-1)

19.0 l/min

Flow rate at 35 K rise

16.3 l/min

Start-up flow rate

2.0 l/min

Flow rate limiter

14.0 l/min

Hot water temperature range

35 to 65 °C

Required connection pressure

0.7 bar

Max. operating pressure (DHW)

9.5 bar

Gas, flue and water connections

Gas connection / max. gas flow (G20)

15 mm / 4.32 m³/h

Permissible gas flow pressure

13.0 to 23.0 mbar

Heating flow / return connections

G 3/4 inch

DHW hot / cold connections

G 3/4 inch

Expansion relief valve connection

15 mm

Condensate discharge hose

19 mm

Air/flue connection

60/100 mm (80/125 mm via alternative connector)

Flue gas temperature

35 to 85 °C

Expansion vessel

10 l, 0.7 bar pre-charge

Electrical

Supply

230 V~, 50 Hz (190 to 253 V~ permitted)

Built-in fuse / external fuse

4 A slow-blow / 3 A

Max. power consumption

98.5 W heating, 134 W hot water

Standby consumption

Under 2 W

IP rating

IPX5D

Dimensions, weight and clearances

Height × width × depth

720 × 440 × 386 mm

Weight

40 kg empty, 44 kg packaged, 48 kg filled

Wall fixing capacity

Suitable for 100 kg load-bearing

Minimum clearances

5 mm sides, 165 mm top (60/100 flue), 180 mm below, 500 mm front

Installation

Indoors only; frost-free location

Supplied in the box

Boiler and fixings

Boiler, unit mounting bracket and fixing material, mounting template

Gas and water

Gas isolation valve, 15 mm gas pipe, DHW connection pipe, 15 mm cold water pipe, 3 service valves

Heating and drainage

2 x 20 mm heating flow/return pipes, condensate discharge hose, expansion relief valve drain pipe and fitting

Extras

Manual filling device with double check valve, small parts bags, documentation

Not included

Air/flue system, controls, system filter

Frequently asked questions

Is the ecoTEC plus 840 supplied with a flue?

No. This listing is for the boiler only. A compatible Vaillant concentric flue (60/100 mm or 80/125 mm) and terminal must be ordered separately, and only original Vaillant air/flue components should be used.

Can the 840 be converted to LPG?

No. The 840 is a natural gas (I2H) appliance and is not on the manufacturer's LPG conversion list. LPG-convertible options exist in the 826, 832 and 836 models.

How much hot water can it deliver?

The boiler provides 19.0 L/min at a 30 K rise and 16.3 L/min at a 35 K rise, with a 14.0 L/min flow rate limiter and a 2.0 L/min start-up flow. A minimum mains pressure of 0.7 bar is required.

Which controls and smart features does it support?

It supports Vaillant eBUS controls, weather-compensated controls, the sensoROOM pure (VRT 50/2) and 230 V or 24 V room thermostats. App control is enabled with the myVAILLANT connect gateway (VR 940f), fitted through the boiler's dedicated interface.

What clearances and installation restrictions apply?

Allow 5 mm each side, 165 mm above (60/100 flue), 180 mm below and 500 mm in front for servicing. The boiler is room-sealed only, not suitable for outdoor installation, and needs a frost-free location. In a room with a bath or shower it must be in zone 2 or 3.

What guarantee applies and what is needed to keep it valid?

Vaillant states that a guarantee of up to 10 years is available when installed by a Vaillant Advance installer (terms apply). The boiler must be serviced annually by a competent person, commissioned with the Benchmark checklist and registered with Vaillant.

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Room Dimensions

Length (in m):

Width (in m):

Height (in m):

Room Type

Living Room

Bedroom

Kitchen

Bathroom

Conservatory

Hallway

Glazing Type

Single Glazed

Double Glazed

Triple Glazed

External Walls

0 Wall

1 Wall

2 Walls

3 Walls

4 Walls

Insulation Level

Poor

Average

Good (New Build)

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