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Vaillant ecoTec exclusive Green iQ 835 Combi Boiler – Review

Today we’re taking a closer look at the Vaillant ecoTec exclusive Green iQ 835 Combi. Try saying that several times over! Here you’ll find all the information you need about the Vaillant ecoTec 835 to help you decide whether it’s the right new boiler for your household.

For those new to the world of boilers, Vaillant is the leading German boiler manufacturer, known for its high-quality engineering. Their closest rival is Worcester Bosch, a UK manufacturer you may have heard of. Vaillant’s ecoTec boilers are the first to be built using eco-friendly and 85% recyclable materials, with full compatibility with the Vaillant vSMART smart thermostat. The Vaillant ecoTec exclusive Green iQ 835 is a premium combination boiler you can rely on, designed to efficiently heat large properties.

Will the Vaillant ecoTec 835 be suitable for my home?

The ecoTec exclusive Green iQ 835 combi boiler is best suited to large, semi-detached and detached houses with around 4 bedrooms and 2 bathrooms. With a central heating output of 35kW, it can comfortably accommodate between 15-20 radiators. In terms of hot water output, it offers a decent 14.5 l/min flow rate. This makes it suitable for those with two bathrooms, wanting to run two showers and a bath. Do keep in mind that your water pressure needs to be high enough in order for the 835 to work effectively. We recommend getting it tested before making your decision.

If your hot water demands are high, you may be better suited to the Vaillant ecoTec 843 combi, which offers an output of 43kW and flow rate of 17.8 l/min. If space is an issue though, it’s worth considering that the 843 will stick out more, as it has a dimension of 474mm compared to the 835’s 406mm.

A similar boiler from an alternative brand is the Worcester Bosch Greenstar 34CDi Classic. It offers a similar flow rate of 14.3 l/min; however, the central heating output is lower at 30kW and you won’t be able to enjoy the climate-friendly qualities of the Vaillant Green iQ range.

Vaillant ecoTec Exclusive Green iQ 835 Controls

The Vaillant green iQ has a simple operator control panel, located under the front flap. This gives you basic control over your boiler’s performance and alerts you to any faults. It’s straightforward enough.

All boilers, including the Vaillant ecoTec 835 must comply with the Boiler Plus regulations, which came into force back in April 2018. These regulations stipulate the level of efficiency boilers must offer, along with the need for both time and temperature controls (as a minimum.)

Combination boilers like the ecoTec 835 are also required to have at least one of these four features:

Weather compensation: Enables the boiler to alter the water temperature based on the temperature outside

Load compensation: Alters the temperature of the hot water produced by the boiler based on the temperature of the room

Smart control: This automates and optimises control of your central heating system

PFGHRD: A Passive Flue Gas Heating Recovery Device

To ensure you are complying with Boiler Plus, it’s a good idea to install a digital thermostat or use a smart controller.

Vaillant’s VRC 700 / 700f Weather Compensating Thermostats are available wired or wireless and work with the complete range of Vaillant boilers. They ensure boilers are always working at peak performance, with flexible time programs and a number of other useful functions, including a holiday program to ensure your heating and hot water do not come on while you’re away.

The ecoTec 835 is fully compatible with Vaillant’s vSMART smart thermostat with its mobile app, which you can download on your smartphone or tablet to take full control of your heating and hot water, from any location. The app learns your preferences and home heating needs to provide even greater efficiency.

ecoTec 835 combi size

The Vaillant 835 ecoTec exclusive with green iQ Combi measures 720mm x 440mm x 406mm. It’s probably a little too large for your standard size kitchen cupboard but should fit seamlessly into a utility room.

If you are looking for a smaller boiler that can be installed in your kitchen cupboard, we recommend taking a look at the a Vaillant ecoFIT pure combi, which has a lightweight, flexible and compact design. This boiler is available with a 35kW output like the 835 but has a slightly lower flow rate of 14.1 l/min.

Vaillant ecoTec Green 835 warranty

As with every boiler, the Vaillant ecoTec 835 comes with a 5-year warranty as standard. If you choose Hometree to install your Vaillant boiler, you’ll receive a 5-year warranty for free with your installation. You can also double up to 10 years for a small extra charge.

With Hometree, you can have the peace of mind that our Gas Safe engineers will provide the best boiler installation solution for your home. But don’t just take our word for it. We are a Which? Trusted Trader and rated Excellent on Trustpilot. The reviews say it all!

ecoTec exclusive 835 energy efficiency

As the name suggests, the ecoTec is about as environmentally friendly as a boiler can get. It has an ErP (previously known as SEDBUK) rating of 89.7%, which is an A-grade overall.

What does this mean for you? It’s good news. ErP stands for Energy-related Products and is the system for rating the energy efficiency of boilers. An A-grade is one of the best you can get. Swap your old inefficient boiler for an A-grade model like the Vaillant ecoTec 835, and you should see a reduction in your energy bills.

Verdict – Is the Vaillant ecoTec 835 the best boiler for your home?

The ecoTec 835 Combi offers fantastic central heating, hot water output and a decent flow rate, making it an excellent choice for a larger family home. It far exceeds many boilers in terms of how many radiators it can handle but doesn’t compromise on its need to be both cost-efficient and environmentally-sound. Get smart and swap your old boiler for the Vaillant ecoTec exclusive Green iQ 835 to start reaping the benefits.

 Vaillant ecoTec exclusive Green iQ 835
ErP rating (energy efficiency)A (89.7%)
Size (HxWxD in mm)720x440x406
Heating output (kW)35
Flow rate (litres/min)14.5
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)43

Which? boiler review

The consumer group Which? review each boiler on the market to find the most (and least) reliable boilers according to a survey completed by thousands of boiler owners. In each review, Which? supply a brand score percentage and star ratings for each category. Take a look at the Vaillant ecoTec exclusive Green iQ 835 Combi boiler ratings below:

Which? Score 
Efficiency rating★★★★★
Brand reliability★★★★☆
Brand customer score★★★★★
Ease of repair★★★★★
Ease of service★★★★★
Availability of parts and spares★★★★★
Build quality★★★★★
Engineer recommendation★★★★★
Brand score80%

Boiler manual

Vaillant ecoTec exclusive Green iQ 835 Combi boiler manual

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