Choosing an unvented cylinder

When choosing an unvented cylinder, it's important to opt for a well-made, high-quality, efficient, high-performance product - else the result might be a disappointed customer and costly, time-consuming call backs. Jon Cockburn, head of marketing at Heatrae Sadia, shares his top product selection tips.

In recent years, an increasing number of manufacturers have brought unvented hot water cylinders to market to capitalise on the demand for high pressure, high-performance hot water. On face value all unvented cylinders might look the same, but closer inspection will reveal important differences. So, it's therefore worth comparing what's on offer, as underperforming products will lead to disappointed customers.

The key things to consider are materials, energy efficiency, performance, product approvals and warranties.

As unvented cylinders store water under pressure, it is essential that they are strong, durable and corrosion resistant. In the UK cylinders are generally made from stainless steel, copper or glass lined mild steel. Cylinders made from mild steel will, however, require a coating or glass lining to make them corrosion resistant. They also need a sacrificial anode, as do some cylinders made from low-grade stainless steel. The anode will need to be monitored for signs of erosion each year.

Duplex stainless steel is by far the preferred material in the manufacture of unvented cylinders, as it has outstanding and unique corrosion resistant properties. It is also lightweight, giving it a strength-to-weight ratio advantage.

We pioneered the use of Duplex stainless steel, and for longer cylinder life we use a combination of laser and TIG welding, and butt joints to avoid crevices, and carry out comprehensive, state-of-the-art post weld treatments.

It's not just the material that the internal cylinder is made from that's important either. On a direct cylinder, a titanium immersion heater is a good indicator of quality, and on an indirect cylinder the material to look for would be Superloy 825. Both are high-grade, but the immersion heater on a direct cylinder needs to be made from a stronger material, as it will be used more frequently than on an indirect model, where the immersion acts as a back-up.

Energy efficiency
In addition, leading manufacturers invest in research and development to ensure their products are energy efficient to meet the needs of today's installers and end users.

And from September 26 this year it has been easier to compare efficiencies, thanks to the energy labels that now apply to water heaters with outputs of up to 70kW and hot water storage tanks with storage volumes of up to 500 litres.

The energy efficiency bands featuring on the labels initially range from A to G, but will eventually extend to A+++, and band G will be removed in 2017. As well as stating the energy efficiency band, directly heated water heaters also include a size (load) profile, ranging from 3XS to 4XL. To provide a few examples, 3XS would be a water heater typically suitable for a small single basin at 35oC, S would be for a shower and single basin at 35oC, M would be for showers and a sink at 55oC, L would be for a bath, shower and sink at 55oC and XXL would be for simultaneous baths and showers.

Manufacturers of all water heaters and hot water storage tanks in the scope of the ErP Directive also have to provide additional performance and efficiency parameters via a 'technical fiche' and within product data, which must be included on company websites and in installation instructions. Energy labelling will make product efficiencies clearer, but it will be important to refer to these technical fiches as well; they will be particularly invaluable when water heating products in the same band are being compared against one another.

Market leading brands will also invest in the performance of their products, whether that's by improving flow rates, recovery times, the amount of stored hot water available or standing heat losses - and this can all be researched and assessed via manufacturers' literature and recommendations.

To provide a few examples of what we do differently; we insulate Megaflo Eco's T&P valve to reduce heat loss, and use an L shaped heating element rather than a straight one to ensure the whole cylinder is heated, and a patented inlet diffuser that ensures excellent stratification and hot water output.

Product approvals
To ensure a product has been properly manufactured, is built to last and will operate safely, installers should look out for hot water cylinders that are constructed and tested to established British and European standards, as well as being manufactured in a factory which has accredited Quality Management Systems. Third party approvals - such as from WRAS and KIWA - demonstrate good quality and performance.

Customers will expect their new hot water cylinder to have a long and reliable life, so ensuring the product has an extended or comprehensive warranty will offer peace of mind that should anything go wrong, they will be covered.

Installers should check the terms of any warranty offered, and any limitations hidden in the T&Cs. Particular things to be aware of are whether onsite parts and labour costs are included, whether the warranty is transferrable to new owners if the property is sold, and what the level of support offered is like - e.g. it's worth looking at the size of the call centre, the opening hours and the level of engineer coverage across the UK.

All unvented cylinders might initially seem the same, but there will be important differences between brands. High-quality products offer the best possible performance, efficiency and innovation and good value for money - and will ensure customer satisfaction in the long run.

Our factory compliance standards

Engineered in Britain.

Trusted worldwide.