Heating and Ventilating

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
In the past couple of years the industry has accepted a huge shift in its thinking with the advent of radiators for low temperature systems.

At one time there were essentially two options, a conventional radiator, which traditionally operated 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 temperature not exceeding 43°C, in line with NHS Estates guidelines.

But temperatures have fallen. The introduction of the condensing boiler, now a legal requirement in all gas system boiler installations, prompted the first major rethink in terms of system flow and return temperatures as the efficiency of the condensing boiler is compromised at higher temperatures.

The downward trend for systems boilers was encouraged further 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 conclusively that radiators do not need to be piping hot, and the radiator for lower system temperature could be adopted far more widely, for use with a wide range of heat sources. By adding additional fins and a greater surface area for heat emission, it was possible to reduce both the water content and the temperature and still efficiently heat a room comfortably for its inhabitants. This new breed of radiator can routinely heat rooms using water temperatures of around 45°C, and in some applications, as low as 35°C.

So the question has become why do we still need safety radiators? And when should we use them?

The simple answer is that we should still be using safety radiators in all the applications for which they were originally designed, particularly for use with conventional heating boilers, whether in new build or refurbishment 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 safety radiator is such that the occupants 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 emitted from the outer casing. 43°C is critical as it is at temperatures above this that prolonged contact can cause scalding or burning to human skin, particularly to delicate skin, as in the case of the very young, the elderly, or those with compromised immunity, 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 temperature 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 acceptable 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 system 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 technologies. As a rule, they tend to be heated by older, traditional technology.

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 temperatures lower than their older counterparts, 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 system temperature, could easily and rapidly reach a temperature not considered safe around the elderly, small children or the infirm.

In these applications, the safety radiator is still a must. To be really safe, they must be correctly installed in line with the manufacturer'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 calculated 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 conceal 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 temperatures fall, in future it is possible to imagine a time when a safety radiator 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 //