Understandably there is currently much talk of energy saving, and in particular, that associated with lighting – hardly surprising since 20% of electrical energy consumed in the UK is used for lighting in one form or the other. Much of the time, talk centres on energy saving strategies achieved through the use of sophisticated electronic controllers or through part of an overall BMS system – invariably linked to light level sensors, presence or occupancy detectors and similar. Undoubtedly, much can be saved by such systems, which must represent the obvious way forward for future new builds.
But what of the numerically huge existing housing and office stock? In many cases the wholesale redesign and installation of a high level system may not be justifiable on a pay-back basis, or from a consideration of the skills required, or disruption involved. For these numerous small and medium sized buildings it may be more appropriate to incorporate simpler control components that could be installed in a phased manner if required, and yet can deliver worthwhile savings by cutting down on the most obvious wasteful lighting practices.
From a company formed to exploit its founder’s patent for a lighting control relay, Finder SpA has since grown to be a household name for such products and today now offers 12 distinct product groups of control components designed to add control over lighting circuits and in doing so, save energy.
So, what aspects of lighting could be considered as ideal candidates for such controls?
Perhaps one of the simplest of applications is that of stairwell lighting where provision of lighting is essential for safety. Switches at every floor would be OK if the user can be relied on to turn-off. Alternatively, PIR movement detectors could be used but several would be required to cover every flight of stairs. Perhaps the oldest solution is to feed the lights through a “staircase” timer – historically a simple momentarily pushed switch, but where the contacts are held closed for a time interval set by a pneumatic ally delayed mechanism. Nowadays pneumatics have been replaced by electronics which in turn allow added features to be offered. In the case of Finder’s 14.01 one selectable feature is the “blink off” option, which gives advance warning over a 20 second interval prior to the light finally extinguishing. Another feature is the “maintenance” function whereby the normal lighting time can be extended to cover cleaning or other maintenance activities. The staircase timer is therefore a simple device, easy to install yet flexible enough to cater for various situations, ultimately cutting the wasteful use of lighting.
Special time switches
In addition to a wide range of 24 hour, daily or weekly programmable time switches, Finder offers more specialised versions.
Whilst there are some applications where the use of electricity is fundamentally a function of the time of day and the particular day(s) of the week (such as water heating), the control of other applications – such as external or horticultural applications – may be more relevantly determined by switching times that vary throughout the year and day-by-day. For these cases it may be better to use an Astro time switch (Finder’s 12.81), where the switching times are linked, not to fixed time of day, but to the sunrise and sunset times experienced at the place of installation. This will be dependent on the seasonal time of year and the longitude and latitude – set by entering either the geographical coordinates, or even simpler, by entering the first part of the UK or European postal code (Finder Patent applied for). Whilst the switching action of the control is primarily determined by the sunrise and sunset times, there is also the useful facility to advance or retard the switching about these Astro times by as much as 90 minutes (in 10 minute intervals).
Special Light dependent relays
LDRs (Light dependent relays) will, as the name suggests, switch according to the ambient light levels irrespective of the time of day or when the sun officially rises or sets. Fundamentally a simple device, there are a few refined version available where the light sensing element may be integral with the relay itself, or it is remote. The latter allows the light sensing to be more closely linked to the light entering a warehouse roof- light for example, or allows it to be less affected by the internal artificial light. This is important to avoid any “hunting” effect of the LDR due to artificial light feedback. An alternative way of achieving a decoupling of the sensor from the artificial light is to use special versions where the LDR’s micro-processor measures and then calculates for the effect of the artificial light and makes automatic correction for this (Finder 11.41 and 11.91 – Finder Patent granted).
“Zero hysteresis” version (Finder 11.41) incorporates special measures to overcome the natural instability that would normally result when having the On and Off switching thresholds at the same level (Finder Patent granted). All these fine tuning measures allow the threshold at which the lighting switches on and off to be more finely set, again contributing to optimising energy saving.
LDRs with Time override
Sometimes the need exists for lighting to be controlled according to the ambient light level as well as an overriding time requirement. Although one could of course use a LDR and Time switch in combination, Finder’s 11.91 is a dual-function device, where it is possible to provide an output when the light level requires it, but subject to certain time considerations. As an example, a shop window display lighting may be required only when the ambient light level is below the set value but overridden to shut off when it is past midnight – when potential window shoppers are expected to be off the street.
But it might also be required that the shop sign, or perhaps low level security lighting, remains on for the full time of darkness. In this instance a second output contact is available which is purely dependent on the ambient light level.
Applications like this can be implemented on a simple case by case basis, and they are probably better served by using a simple stand-alone control component rather than trying to integrate within a wider system or network.