As our starting point, we are assuming that the linear LED fixture consists of a continuous LED tape mounted within an aluminium profile. With this in mind, there are three basic types of continuous linear LEDs available to you.
Standard – measured according to available profile lengths and used individually with a power cable to each fitting. These standard lengths can usually be cut to shorter lengths, either by the manufacturer/supplier or by the installing contractor.
System-specific – Profile lengths can often be connected together, where longer lengths are required. One power source can power many metres of LED channel, depending on design. System-specific arrangements can also integrate angles allowing the profiles to create different designs such as zig-zags. Always ensure that you know how the electrical connections between channels are to made. Of all the things that need to be decided when looking at continuous linear LED installations, this can be the greatest headache – and lead to the greatest satisfaction when it is done well.
Bespoke manufacture – LED channels can also be curved to provide more dramatic lighting effects. These designs are often designed to integrate into architectural details and accurate measurements for fabrication are vital. The issue of electrical connections still stands!
The LED tapes that fit inside the aluminium profiles are available with different spacings between the LED chips, known as the LED ‘pitch’. The shorter the pitch, the less ‘spottiness’ is seen on the channel diffuser. The pitch also determines where the LED strips can be cut to required size. A 50mm cutting length is common, with LEDs spaced at 7mm intervals.
Specifying the colour temperature is the same as with any LED luminaire specification. There is a wide range of CCTs available, typically from 2700K to 6500K. RGB, RGBW and tunable white versions are also available.
Colour rendering is also variable. Good quality LED tapes start at >CRI80, though the tendency is not towards >CRI90 as the general quality of LED lighting improves. And don’t forget that TM30 metrics are becoming more popular among specifiers because of the greater accuracy in the testing process.
Colour accuracy will also require you to take things a bit deeper, looking at factors such as the accuracy of MacAdam ellipses in the binning process. Having a row of LED’s in linear lighting, it is of paramount importance that they are all exactly the same colour, from the same bin/batch and of a high quality. This is something that should be considered when writing a specification.
Finally, if there is ever going to be a challenge with continuous linear lighting it is likely to be light bleed, where light manages to squeeze out between the cut edges of two channels. Before the project gets to that point, check samples of two connecting pieces to see how the manufacturer intends to deal with this. Good manufacturers have putties to seal gaps and use mechanical couplers to connect two channels seamlessly
If you are considering higher IP ratings, its worth knowing that the cost impact on this type of fixture can be high. IP68 LED tapes can be fitted into aluminium profiles but that doesn’t remove the importance of ensuring that the entire system performs to that standard.