What type of boiler is the Viessmann Vitodens 100-W 35kW - regular, system or combi?

The Viessmann Vitodens 100-W 35kW is a combi boiler you may wish to consider if you want this particular type of boiler for your house or flat.

The UK has some of the smallest homes in the Western world, which is partly why combi boilers were introduced in the 1970s. Traditional boilers require one or more large storage tanks which they use to either heat water and keep it warm or store water intended for heating later. These tanks took up a lot of space in people's homes.

Combi boilers save space because they don't require these tanks to operate. Instead, combis draw water direct from your mains supply then instantly heat and distribute it on demand.

The biggest disadvantage in using combi boilers is that they have a maximum capacity volume for heating water. While this may not be an issue in a small household, it could be for a larger household where there is higher demand for hot water. When more than one person is using the water, it is distributed between the two points, reducing the pressure and temperature at each point.

Is a Viessmann Vitodens 100-W 35kW combi boiler right for my house or apartment?

Whether this Viessmann Vitodens 100-W 35kW Combi boiler is right for where you live depends on its size or what its "output" level is. Size does not mean its physical dimensions, however - it means how powerful it is.

The output of a boiler is measured in kilowatts and indicates how much energy it can use to heat the water needed for your radiators, taps and showers. The greater the output, the more water it can heat.

A boiler whose output is too high will give you hot water and warm radiators but also higher gas bills, whereas a boiler whose output is too low will result in cheaper gas bills but the water might not always be as hot as you want it to be.

The output of the Viessmann Vitodens 100-W 35kW combi is 35 kW, so which types of property would this model be appropriate for?

An experienced Gas Safe boiler installer would be likely to recommend that this Viessmann Vitodens 100-W 35kW Combi boiler is capable of providing heating and hot water to 15 or more radiators and two or more bathrooms and would therefore be most suitable for larger properties including detached homes.

With combi boilers, you need to consider the flow rate as well as the output rate. The flow rate (shown in litres per minute) measures how much water your boiler can draw from the mains which it then instantly heats and distributes to your taps and radiators.

However, a high flow rate is of little to no value if your local water pressure is low. If your local mains water pressure is 10l/m and your flow rate is 12l/m, your boiler will only be able to process 10l/m.

If you live in an area with high water pressure but your household has multiple bathrooms and/or radiators and many members of your household want to use hot water at the same time (like morning or evening baths or showers), it's unlikely that you'll be able to find a combi with a high enough flow rate.

As an indication, a power shower needs about 10 litres of water per minute, whereas the flow rate of this Viessmann Vitodens 100-W 35kW Combi boiler is 17 L/ml/m.

When our engineer comes out to quote you, they may recommend that you choose a heat only boiler or system boiler instead if your family's demand for hot water is higher than normal.

Making space for the Viessmann Vitodens 100-W 35kW

The dimensions of the Viessmann Vitodens 100-W 35kW are 455 mm tall, 595 mm wide, and 800 mm deep.

Viessmann Vitodens 100-W 35kW – condensing or non-condensing?

The Viessmann Vitodens 100-W 35kW is a condensing boiler – we recommend to all clients that they choose the very latest condensing boilers because their efficiency continues to improve year after year.

Condensing boilers recycle heat from both water vapour condensation and flue exhaust gases via a secondary heat exchanger. With this heat, it performs other tasks like warming up colder water returning from your radiator without having to use more gas.

You will save money on your gas bills every year by choosing a condensing boiler as well as benefitting the environment.

Does the Viessmann Vitodens 100-W 35kW combi protect the environment?

With growing concern among the public about accelerating climate change, how we heat our homes and the impact this has on the environment has become a major topic of concern for many homeowners.

The heating of our homes accounts for 14% of the UK's greenhouse gas emissions. Especially in the big cities, gas boilers are responsible for dangerous levels of nitrogen dioxide emissions.

Is the Viessmann Vitodens 100-W 35kW combi boiler an environmentally friendly choice for your home? Here’s what the figures say.

All new British boilers must perform to a legal minimum energy efficiency of 92% (a low to good SEDBUK "A" rating). Prior to April 2018, the target was 88% (86-90% = SEDBUK "B" and 90%+ = SEDBUK "A").

Efficiency ratings are intended to let consumers know how much energy a boiler uses in its day-to-day activities and how much energy goes to waste.

The Viessmann Vitodens 100-W 35kW was awarded an efficiency rating of 94%, equivalent to a SEDBUK grade of "A".

The ERP, short for the Energy Related Products Directive, is a European directive aimed at encouraging manufacturers to create products that are environmentally friendlier at all stages, including during manufacturing, when the product is in active use, right through to the point of final disposal.

The Viessmann Vitodens 100-W 35kW has a rating of "A" for heat and "A" for hot water production.

Is there a warranty on the Viessmann Vitodens 100-W 35kW combi boiler if it breaks down?

On the Viessmann Vitodens 100-W 35kW, the manufacturer offers a parts and labour warranty of 5 years.