Commercial heating Safety in temperature
With the industry taking the radiator for low temperature heating systems to its heart, do we still need low surface temperature radiators? Barry Lynch explains why the low surface temperature radiator is still the optimum choice in certain situations
couple of years the industry has accepted a huge shift in its thinking with the advent of radiators for low temperature sys- tems. At one time there were essen- tially two options, a conventional radiator, which traditionally operat- ed at flow temperatures of up to 82°C and returns of around 71°C; or, in cases where extra care was needed, a specially designed low surface temperature safety radiator. The latter will deliver a surface tem- perature not exceeding 43°C, in line with NHS Estates guidelines. But temperatures have fallen. The introduction of the condens- ing boiler, now a legal requirement in all gas system boiler installa- tions, prompted the first major rethink in terms of system flow and return temperatures as the effi- ciency of the condensing boiler is
compromised at higher tempera- tures. The downward trend for sys- tems boilers was encouraged fur- ther by the growth of the use of renewable heating technologies and heat sources such as ground or air source heat pumps. Initially, opinion was inclined to think that this meant the end of the radiator as a main source of room heating, but this turned out not to be the case.
Research commissioned by
Purmo at the Helsinki University of technology demonstrated con- clusively that radiators do not need to be piping hot, and the radiator for lower system tempera- ture could be adopted far more widely, for use with a wide range of heat sources. By adding addi- tional fins and a greater surface area for heat emission, it was pos-
sible to reduce both the water content and the temperature and still efficiently heat a room com- fortably for its inhabitants. This new breed of radiator can routine- ly heat rooms using water temper- atures of around 45°C, and in some applications, as low as 35°C. So the question has become, why do we still need safety radia- tors? And when should we use them?
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The simple answer is that we should still be using safety radia- tors in all the applications for which they were originally designed, particularly for use with conventional heating boilers, whether in new build or refurbish- ment projects. The safety radiator comprises two main parts, an inner radiator and an outer casing, with a set distance between the two. Designed to ensure that its surface temperature does not rise above 43°C, the construction of the safe- ty radiator is such that the occu- pants of a room cannot actually come into contact with the heat emitter itself, only the outer casing. A built-in barrier of air within the casing allows only a restricted amount of surface heat to be emit- ted from the outer casing. 43°C is critical as it is at temper- atures above this that prolonged contact can cause scalding or burning to human skin, particular- ly to delicate skin, as in the case of the very young, the elderly, or those with compromised immuni- ty, limited mobility or certain underlying health problems. For many years, therefore, in nursing and care homes, nursery schools, day care centres, hospitals and clinics, safety radiators have been the standard requirement. With the advent of radiators which are suited to low tempera- ture systems, some confusion has arisen. If they are able to provide comfort heating at 45 or even 35°C, it is easy to see why it could be perceived that it is equally accept- able to specify these in place of a low surface temperature radiator. This is not the case and there is an inherent danger in substituting a radiator for low temperature sys- tem for a low surface temperature
radiator. The danger, ironically, is in the former’s energy efficiency. Few care homes or hospitals are heated by use of renewable tech- nologies. As a rule, they tend to be heated by older, traditional tech- nology. Even if they use modern boiler plant, the vast majority of heating systems in care homes, nursery schools and hospitals depend on conventional heating systems. Most are well managed and will run on system tempera- tures lower than their older coun- terparts, but it will be impossible to guarantee that they will not be run at temperatures higher than 43°C. When they are, the modern radiator, designed to emit as much heat as possible from a lower sys- tem temperature, could easily and rapidly reach a temperature not considered safe around the elder- ly, small children or the infirm. In these applications, the safety radiator is still a must. To be real- ly safe, they must be correctly installed in line with the manufac- turer’s instructions. There can be a temptation to adapt outer casings to make them shallower or more compact, but the distance between the high efficiency heat emitter inside the appliance and the outer casing is precisely calcu- lated to allow sufficient heat to radiate through the outer casing to heat the room, but not to allow the front, or the top or side grilles, to overheat and pose a danger. Care must also be taken to con- ceal or box in exposed pipework leading to or away from the safety radiator. The safety radiator casing is designed to enclose pipework that rises out of the floor, but in any installation where there is exposed pipework running above ground level, additional care must be taken to ensure that the pipework itself must also be made safe. As system efficiencies continue to increase and system tempera- tures fall, in future it is possible to imagine a time when a safety radi- ator might not be so essential to safeguard the vulnerable. For now though, better safe than sorry.
// The author is the sales and marketing director of Purmo //
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