The OSO 20 series is a stainless steel unvented cylinder specifically manufactured for UK water conditions and regulations. The “bubble top” design has proved increasingly popular over a 15 year period and has seen OSO transformed from an unknown entrant to the UK water heating market to one of the most popular and highly respected suppliers in the country.
 
No expansion vessel required: The 20 series differs from most other unvented cylinders in its use of the “bubble top” principle that eliminates the need for a separate expansion vessel. A bubble of compressed air is trapped in the top of the cylinder when the product is commissioned and this air cushion allows water to expand internally within the cylinder walls. The resultant installation is neater and more space efficient than other cylinders and allows far more room for storage and airing when the cylinder is fitted in a typical British airing cupboard location.
 
High performance: OSO 20 series cylinders are an established market leader in cylinder performance and efficiency. The 12m long 26kw heating coils fitted in cylinders from 170 litres upwards capable of heating all but the largest size in the range in less than 30 minutes. The substantial surface area of 0.94m2 not only speeds up heating time but also assist condensing boilers to stay in condensing mode for longer, thus saving valuable fuel. The factory fitted polyurethane foam insulates the hot water well and contributes to impressively low heat loss figures.
 
OSO 20 series products have a strong reputation for build quality, supported by a 25year guarantee. OSO have been using Stainless steel construction methods for nearly forty years and have produced over 2 million cylinders in this time. OSO’s experience has seen the company expand in recent years beyond its Norwegian home to many other countries around Europe and the world, with the UK being an important export market.
 
Easy installation: 20 series units are renowned by the plumbing trade as being very straightforward to install. A full fittings pack is supplied, with every component fashioned to save labour for the installer. The Multibloc valve includes the pressure reducing valve, line strainer, check vavle, balanced cold water point and expansion relief valve. The drain point is coupled with the cold feed elbow and a flexible hose is supplied to link the expansion relief valve to the tundish. At 580mm diameter, the cylinder is wider than some other units, but occupies a compact footprint due to efficient use of space and will easily fit in standard airing cupboards. The more squat nature of the cylinder however has considerable advantages with the cylinder occupying less height than competitors and leaving more usable space in the cylinder cupboard.
 
The 20 series offers further flexibility by being able to be “fully flooded”. This simple process allows the cylinder air bubble to be removed by the installer at installation or at a later date. Cylinder capacity is increased by 20% as the air bubble area is used for water storage. Whilst the great majority of OSO units will remain as bubble top, the fully flooded option is available as a problem solver in certain circumstances, such as where greater volume is needed or there is a height restriction in the installation area.
 
The 20 series is available in direct and indirect heating formats and 6 sizes from 100 to 330 litres. The products are independently approved by BBA and WRAS.
 
Eco-friendly production: The 20 series is manufactured using laser welding technology, which requires no filler rod. The welds are created in an oxygen free atmosphere, thus eliminating the need for cleaning of corrosive oxides on the weld, typically done by acid washing in competitor factories, with consequential environmental damage. Oso laser welding eliminates these harmful discharges from our factory. Cylinders are insulated using polyurethane foam to minimise heat losses. The foam is created using water as blowing agent to minimise harmful emissions and give a zero Ozone Depletion Potential.