LED Lighting Guide

A quick LED lighting guide and what to look for when buying LED Lights

This LED lighting guide is aimed at providing the information needed to make a sensible and informed decision when buying LED lighting. Each of the headers below is covered in more detail further down the page.

LED Lighting Warranties – fittings should be around the 50,000 hour mark with 30,000 hours on retrofit lamps/bulbs (see below)

Replacing Faulty/Damaged LED Light Fittings – if the light fitting is part of a scheme of multiple fittings always understand if you will be able to get another one the same in the future if it fails

Lumen Maintenance/Degradation? – Lumen Maintenance should be around L7, (70% of the lumens, (light output) remain over the life of the fitting)

Binning in LED Lighting – Binning is a process used to match colours of LED’s, the better the binning the more accurate the colour.

Colour Rendering Index (CRI) – Measured on a scale 0 to 100, 100 being true daylight.  >80 is always recommended for any areas where good colour representations are required.

Enhanced Capital Allowance Scheme (ECA) – A government run scheme allowing purchasers of compliant lighting schemes to claim back 100% of the capital spent within the first tax year.

Chip Lumens and Luminaire Lumens –are terms used to measure light output from a source.  Always compare luminaire lumens not chip lumens when selecting fittings.

Luminaire Watts and Circuit Watts – This indicates the efficiency of a fitting, the more lumens per Watt of electrical power consumed the more efficient the fitting.

Controls – many control systems are available for lighting schemes.  If you are investing in low energy lighting to save money or reduce your carbon footprint then controls must be considered in the first instance.

Retrofitting/Replacing Exiting Lighting Schemes with LED lights – always check before replacing existing lighting schemes with LED’s that the design is good.  Get it wrong and you may end up with over lit areas wasting money or dark patches where lighting is poor.

Other Areas for Consideration on Retrofit Projects/Schemes – Voltage Optimisation, (VO) and control systems may return greater savings than replacement fittings.  Always consider all options.

Monitoring – It is always good practice to fully understand load profiles in order to correctly assess where the energy is being used and therefore where to target energy saving budgets.  Monitoring existing and new schemes can provide invaluable data in the feasibility and analysis stage of any large capital expenditure project.

 

1) LED Lighting Warranties

Warranties are provided by the Manufacturer.

There is no desire from insurance companies to underwrite LED products as they are too complex with too much to go wrong and far too much to argue about in the instance they do go wrong.  So it is unlikely to find LED light fittings with insurance backed warranties, but if you do then the T&C’s would require close scrutiny.

So regards warranties, five year/50,000 hour warranties are common place in the LED industry and I think it is fair to say that this would be the minimum expectation on most fittings with retrofit lamp warranties averaging around the 30,000 hours mark.  Longer warranties are available but the front end fitting costs generally reflect the extended period.  Personally I would go with a recognised manufacturer with a long well established trading history within the lighting industry who has something to loose.  This means the length of the warranty should not come into play.  My recommendation would be a UK based company at best, or a solid company in either Europe, Japan or the USA with a good established trading history within the lighting industry who has a UK presence.  If due diligence is done on the manufacturer then in my view you stand a better chance of resolving any issues with a reputable company who you can talk to in English than any lesser known one abroad.  My own experience with reputable lighting companies is that they are more than willing to assist in any way they can to uphold there good name.  They are not interested in complaints rumbling on indefinitely leaving behind disgruntled customers who will never purchase their products again. 

LED light fittings are going out of fashion quicker than a catalogue can be printed.  So getting a manufacturer that can be relied on is crucial when planning large schemes based on payback.

All LED providers should be capable of supplying evidence of the points below with ease.

2) Replacing Faulty/Damaged LED Light Fittings

When selecting a fitting, check it will be supported throughout its rated life or at least its payback period in case of fitting failures.  The fitting employed should be readily available.  If the fitting manufacturer is based abroad then check if they have a UK base and they have a solid background.  Ask yourself this, what will happen if the supplier/reseller is no longer trading?  You can’t just change a lamp in an LED fitting, the whole fitting will generally require replacing.  If you cannot get a replacement fitting the same as the one installed it may leave the scheme looking odd, and the more that fail the more odd it will look.

3) What is Lumen Maintenance/Degradation?

Good “lumen maintenance” is critical when planning long payback schemes. 

Lumen maintenance is the light level output degradation over time and sometimes prefixed by the letter L.  A decent lumen maintenance is L7 which means the fitting is guaranteed to output 70% of the average rated lumen output at the average lamp life of the fitting.  So in plain English, if a fitting has a lamp life of 50,000 hours and an output of 15,000 lumens then the lumen output at 50,000 hours would be 10,500 lumens, (70% of 15,000).  This is sometime referred to as “lumen degradation”.  These figures can fall as low as 30% on some poorer quality fittings, do not accept anything less than 70%.

 4) What Does Binning Mean in LED Lighting?

This refers to the selection process of LED’s where LED’s of the same colour are binned together at manufacturing stage.  Poor binning means poor colour matching between fittings.  If LED’s from a wide colour spectrum are chosen to make up the array of LED’s in a single light fitting then it stands to reason that the overall colour of the output will be a mixture of all the colours of the various LED’s used.  If the LED’s are tightly binned, i.e. all the same colour in the same array then the output colour can be controlled much more closely and accurately represent the colour specified.  If you have several fittings adjacent each other in an office for instance you would want good binning so they all output as close as can be realistically expected the same colour.

5) What is Colour Rendering Index (CRI)?

The CRI of a light source indicates its ability to best replicate true colour as it would be seen under natural light.  CRI values are given on a scale of 0-100, where 100 is natural light.  Triphosphorous fluorescent lamps have a CRI value of up to 90.  Any fitting chosen for an area where colour renditioning is of interest then choose a fitting with a CRI of at least 80 to represent the colours well as they would be seen in natural light.  LED fittings can be manufactured in almost any colour of the lighting spectrum, (CCT, Correlated Colour Temperature measured in Kelvin).  Noon daylight is considered to be around 5500 Kelvin and would be chosen where good natural colour representation is required such as in the printing industry for instance.  4000 Kelvin is generally used in office type applications, 6000 Kelvin is blueish, all are common place in the LED market. Colours below 4000k are generally considered as warm with colours below considered to be cool.

6) What is The Enhanced Capital Allowance Scheme (ECA)?

The fittings should be eligible for the Enhanced Capital Allowance scheme (ECA), which gives the option of writing down the fittings in the first tax year in full.  In order to gain access onto this list the fittings must have a CRI value equal to or greater than 80.

7) What are Chip Lumens and Luminaire Lumens in LED Lighting?

Chip lumens are measured in front of the chip, (light source), whereas luminaire lumens are measured after any controller i.e. Perspex diffuser.  The net effect of this is considerable as you can probably imagine.  Any controller which is designed to disperse the light can also significantly reduce the lumen output, so lumens should always be measured after any controller, (luminaire lumens).  If a fitting has “fitting lumens” stated on a data sheet always request the “luminaire lumens” in order to compare as this is measured after any front Perspex cover or diffuser.

8) What are Luminaire Watts and Circuit Watts in LED Lighting?

Comparing circuit Watts and Lumen Watts can give an indication of the internal electronics quality.  Basically, the closer these two figures are to each other the better the efficiency of the internal control gear.  This has no bearing on the lumen output though.

9) Retrofitting/Replacing Exiting Lighting Schemes with LED lights (a word of warning)

Care should be taken when replacing lights on a like for like basis.  The existing fitting spacing to height ratio would have been originally designed for that particular type of light fitting/lamp source and its photometrics’, (the way/shape in which the light is distributed).  Simply replacing the fitting with another may give some unforeseen results if the photometrics of the replacement fitting are vastly different from the one being removed.  For instance, the lumen output of the proposed new fitting may look favourable on paper when a direct comparison against the existing fitting lamp is made.  However, in reality the footprint of the light output at the target height may be considerably different, leaving some areas dark and other areas over lit, (poor uniformity). 

There is no one rule for replacement LED fittings i.e. a 140W replaces a 400W fitting due to the reasons explained above.  Each project will require considering on its own merits.  Having a selection of LED fittings at your disposal with different lumen outputs and photometric designs is advantageous.

10) LED Lighting Design and Other Areas for Consideration on Retrofit Projects/Schemes

Sometimes areas are over lit and significant savings can be made by simply reducing the number of light fittings or reducing their output.  Simple control systems can help, with even something as simple as a timer having a significant effect.  Significant savings can be made by incorporating natural light into a lighting design.

Where it is cost prohibitive to replace lighting in some areas Voltage Optimisers may return good savings.  On an average discharge type installation savings of up to and around 12-15% can easily be achieved by the use of such devices.  They can pay back in under six months in some favourable cases due their relatively small front end cost and simple installation and therefore provide a quick fix to a complex area or hard to access environment or where installations have a short life expectancy due to future plans.

 

Whilst most energy saving lighting schemes are installed for economic reasons, carefully implemented and thought through revised lighting schemes can bring further benefits, not just financial ones.  For instance, a lighting scheme using all the latest computer aided design and carefully selected fittings will most probably significantly improve the overall distribution of light and thus improve the environment for people in the area.  Modern installation techniques and equipment can vastly improve the utility of an area where more flexible distribution systems are used.  For instance, in an assembly area where area utilisation can change frequently, a lighting bus bar system may be employed which makes switching arrangement alterations easy and economical where previously such alterations would not be considered due to the prohibitive cost of extensive wiring alterations.  The new switching alterations may make the system pay back even quicker than would otherwise be achievable, where lights may be left on in areas not used.  The same system can allow for quick alterations to be made in the layout of a new production line for instance where lights can be unplugged and quickly relocated by simply unclipping and clipping back into their new location on the us bar with no expensive wiring alterations or skilled people required.  All these points should be taken into consideration when planning significant alterations to an existing scheme as the short term capital costs can soon be recovered by expensive maintenance and alteration costs which may be occurred later but not factored in to the new scheme costs.

 

Prepared by: Craig Gascoigne – August 2015

NICEIC Approved Electrical Contractor