Mike Wright explores the technology behind low surface temperature radiators, and explains what the flourishing market means for installers.

Designed to provide safe, effective and reliable heating for vulnerable people in both domestic and commercial applications, the market for low surface temperature (LST) radiators has seen steady growth in recent years.

This is partly driven by ever-tightening safety regulations – not least the NHS Safe Surface Temperature guidelines, which stipulate that the surface temperature of radiators in NHS buildings should not exceed 43°c. With such stringent safety criteria in place, it’s vital that any heating and plumbing professional working in public buildings stays on top of LST technology: how it works, where best to use it and the applications driving uptake.

Balancing safety and performance

In a conventional hot water system – one with an incoming flow temperature of 90°c and a return of 70°c – radiator surfaces can reach temperatures of 80°c, and once skin comes into contact with this surface, it can take less than a second for burns to occur. LST radiators have been developed to incorporate a specialist casing, dramatically reducing the risk of serious injury from prolonged radiator surface contact.

Obviously, reducing the surface temperature by such a significant amount delivers a whole host of benefits when it comes to user safety – but for the radiator to do its job, it’s still essential that it emits enough heat to keep the building and its residents warm and comfortable. To guarantee that a lower surface temperature does not mean lower performance, LSTs are built to allow sufficient ventilation (and minimal heat loss) through the casing. As such, most models on the market today feature strategically placed ventilation grilles, which are designed to draw in cold air from the bottom of the casing and create a ‘chimney’ effect – optimising the level of heat transfer through the grilles at the top by convection. At the same time, the special LST casing suppresses radiant heat transfer, ensuring the surface temperature stays within the safe-touch guidelines.

Design considerations

For improved safety – especially in environments where children have access to radiators – an LST’s grilles should be wide enough to encourage proper air circulation, but narrow enough to stop foreign objects from falling or being pushed through into the casing. Grilles like these are sometimes referred to as being pencil proof. For certain applications, it may also be necessary for all of a building’s fixtures and fittings to be anti-ligature. If in doubt, ask your manufacturer whether your chosen LST meets the relevant requirements.

In terms of operation, it’s crucial that end users can easily control the temperature of each LST unit without opening the cover and exposing the emitter underneath. With this in mind, it’s always best to opt for a system with an external thermostatic radiator valve. These can be connected directly to the emitter via a made-to-measure cut-out in the casing, or, for added tamper-proof security, the LST can be fitted with a remote sensor head outside the casing, which is then connected by capillary to the valve inside. Some models also feature a lockable casing that incorporates a hinge mechanism – delivering protection for end users but also making for straightforward access when it comes to maintenance, repairs or cleaning.

A growing market

Newbuild developments have traditionally made up the bulk of the LST market, and as the January 2016 Building Information Modelling deadline approaches, it is becoming easier than ever to design and size new LST systems to meet the exact requirements of individual projects.

However, nowadays some manufacturers offer fully compliant LST casings that can either be installed together in a package with their own new heat emitter, or mounted onto a suitable existing radiator as a separate component. These could also be specified as a replacement for an outdated or damaged LST.

This means that modern LSTs are as suitable for retrofit projects as they are for newbuild – and the opportunity for installers has never been greater.

While it’s mandatory to opt for LST radiators with surface temperatures not exceeding 43°c for all NHS applications – including hospitals, clinics and other health centres – their unrivalled safety levels also make LSTs a suitable solution for any public or private building that’s occupied or used by people who may be at risk of burning themselves. This includes nurseries, schools, care homes, prisons and sheltered accommodation. There is also an expanding market for general domestic applications – including newbuild housing – as developers make decisions that will help make homes as accessible as possible for a broad spectrum of residents.

In such a thriving area, what becomes instantly clear is that continuing to develop product knowledge and technical expertise should be a priority for installers. Only those who are fully aware of the technology available – and the widening scope of applications that can benefit from LST radiators – will be properly equipped to make the most of the growing opportunity at hand.

Mike Wright is product development manager at Quinn Radiators.