Size, Safety and Compliance: Why there is more to specifying an unvented cylinder than first meets the eye

Multiple issues determine what hot water system is specified. Is there access to natural gas? Does the development consist of properties with more than one bathroom? Is space at a premium? Does what is specified comply with current regulations?

Size is invariably one of these issues. For example, will it fit in a standard cupboard? Unvented cylinders from every manufacturer tend to vary in height and diameter. The height can vary from 900mm for a cylinder that is only suitable for a one bedroom one bathroom apartment to almost 2 metres for a 300 litre cylinder which is suitable for a 4 bedroom 4 bathroom house.

Does the size issue stop at the cylinder dimensions that can be found in every manufacturer’s marketing material? No. The architect and consultant need to take into account the cold water supply; domestic hot water outlet; primary flow and return; Multibloc; motorised valve and expansion vessels if internal expansion isn’t being used. All take up valuable space.

OSO Hotwater (the largest manufacturer of unvented cylinders in Europe) has decided to resolve this and other conundrums facing the specifier.

Using an innovative patented Sole blending valve, all pipework coming from the rear of the cylinder and a cavity with neat protective lid these issues are solved. The Sole valve blends stored water down from 70^oC to 60^oC meaning ~20% more usable hot water! This means that a smaller cylinder can be specified freeing space.

Safety in the hot water storage industry includes the prevention of scalding and legionella as well as the integrity of the cylinder itself. Legionella is able to survive, and grow at temperatures between 18^oC & 45^oC. By blending down from 70^oC to 60^oC OSO Hotwater cylinders not only save space, but prevent legionella growth. The Multibloc also has 3 temperature, pressure and expansion relief valves factory-fitted, which protects against pressure surges that could cause other cylinders to explode.

Of course compliance is a major issue. SAP determines how much insulation, or the U values of windows to specify; the same is the case for unvented cylinders. Currently energy efficiency which is determined by heat losses over a 24 hour period permit cylinders that have E, F and even G rated cylinders to be specified. ErP changes this. From September 26^th 2017 only cylinders rated between A-C will be legally compliant. Many cylinders will cease to exist as changing manufacturing processes is costly. One argument is “just add extra insulation”. This is possible, but the PUR foam insulation (which is ubiquitous throughout the industry) would mean that manufacturers would have to be double or triple the thickness of their existing insulation! The issue of space raises its ugly head again!

As the most design conscious manufacturer within the unvented cylinder industry OSO Hotwater has come up with an answer. Our latest Delta A range has an integrated vacuum insulation panel which essentially works like a Thermos. At only 25mm thick all Delta A cylinders from 120 litre to 300 litre cylinders are A-Rated. OSO Hotwater is proud to be the only manufacturer to achieve this.

OSO Hotwater provide industry-leading CPDs on the specification of unvented cylinders. If you are interested in booking a CPD, please contact the sales office on 01914820800.