Questions to ask when buying LED Lighting

December 19, 2016

 

Over recent years there have been many new LED lighting products introduced to the market.

 

Some of these are of excellent quality, built to comply fully with all relevant standards, however there are also some which are untested for use in EU working environments, or are unreliable and possibly unsafe with no genuine CE certification.

 

Within the industry we have also seen a large number of demi-compliant luminaire built from kit parts. The assumption being that the finished kit part product would pass LVD certification, despite not being tested or certified as the finished/complete supplied product. While many of these kits may pass full CE testing, there is an element of risk and liability, also the kit maker may not be aware of the full technical requirements in order to make the product fit for purpose for its intended application.  

  

Below is a guide to assist you in asking the right questions in order to improve the chances of avoiding buying non-compliant products.

 

CE certification

 

CE markings and certificates can easily be forged– it is good practice to check that the test house exists and has full accreditation:

  • Are they registered as UKAS accredited (for UK) or china national accreditation service (CNAS)?

  • Is the product registered on the TUV online system?

  • It is good practice to have an engineer compare the CE test results from the LVD and EMC reports with a sample of the product to make sure test information matches the product supplied.

We have seen manufacturers which claim to have TUV certification for a product range – but only have one product certified by TUV. This can be misleading as it would appear that all the products in the range have this qualification. We recommend checking with TUV online to see which products have been certified.

 

Be aware, it has been noted, that companies can swap product names/model numbers when selling. This results in supplying a non TUV product that uses the name/model no, of the company’s one TUV certified product. The best practice is to check everything – that the product is on the TUV site, and the TUV report number online matches the report number of the LVD/EMC/RHOS reports which also have the same production, report images and the same electrical characteristics.      

  

LVD and EMC reports include a photograph of each actual unit tested and the internal circuit boards. At the minimum you can make sure the images on the report match the supplied product. People have seen cases where the photographs of another product have been copied and pasted into the report!  It is good practice to have the reports looked over by an engineer, preferably conducting their own tests/examination of the product to ensure its validity.

 

While a declaration of conformity from the manufacturer puts the legal responsibility of ensuring the tests done are valid – it would be of little consolation to the user if the manufacturing company simply disappeared. Taking legal action in China from the UK could be difficult and expensive and the importer could end up having to deal with the legal implications alone.

 

Importing companies must perform their due diligence for their own sake and the customers.

 

Important note: All LED luminaires must have:

 

EN 62471:2008 Photo biological safety - Blue light radiation -bio hazard certification
EN 62493:2010 Exposure to magnetic fields, EMF- bio hazard certification

 

It is now illegal to put a CE mark on a product if the EMF/photo biological certification is not included.

 

Unfortunately, there are a large number of imported luminaire products that do not have these standards. Some Chinese manufacturers do not conduct the EN 62471:2008 test, they take it from the LED’s data sheet, that the LED does not emit high UV light levels under normal drive currents /voltages. However, this may not be the case when the LED is working in the product.

 

We find there are manufactures who do not conduct these tests, and make an assumption of compliancy instead. Some are not up to date with current changes in required CE standards or EU directives, this could be the result of a language barrier, but any Chinese manufacture can consult a Chinese test house to ensure their products are up to date. For some smaller companies, it is a financial decision as testing can be very expensive.   

 

It may be that the majority of products that do not have EN 62471:2008, would probably pass, however, it is illegal to include the CE mark without EN 62471:2008 certification, as EN 62471:2008 is a requirement of the LVD directive.

 

The possible implications of this are as follows:

  • if an installation site has a problem, even if the product is not the cause, the site owner could check and find out the EN 62471:2008 certification has not been included and rightly state that the product has been placed onto the market without full compliance to the LVD directive and therefore has a false CE mark, this could then result in legal action.
     

  • There could be a variation in the product’s output voltage/current, which causes the product to emit harmful UV radiation – this would be a serious concern for all. 

In some cases, products that were introduced many years ago may not have had their standard updated – the manufacturers should keep themselves informed of changes in EU certification requirements and directives.

 

In most cases, you can ask the manufacturer to update the certification and they will.

 

Why are some products cheaper?

 

It is tempting to buy the cheapest product but beware! Some manufacturers have been known to omit safety and filtering circuitry to lower their product cost and forge CE certificates/testing to save money. It is important to know which products are cheap and dangerous and which products give good value with good safety/reliability and performance.

 

Some companies can also reduce cost by not conducting all the CE tests required.

 

We have seen cases where a manufacturer has changed the components to cheaper ones after the CE testing – so the supplied products was not as safe or reliable. MG Lites conduct regular inspections comparing the delivered product to the test reports to ensure no alterations have been made.  

 

Whenever specifying a luminaire product we recommend seeking professional advice as to which relevant standards the product must have – these vary with type/class and application of the product in question. 

 

LEDs

 

Q- Does the manufacturer use a reputable make of LED?

 

E.G. Cree/Epistar /Osram/Lumiled/luminmax etc.

 

A reputable name is always a good thing, but if the LED make is not a brand name, but has good LM80 testing results, it can be just as reliable as a brand name LED, providing the manufacturer can produce large quantities with good consistency.

 

Q- Are the LEDs in the product being driven correctly (below the max, ratings)? 


Can the supplier provide evidence that the LEDs are not being overdriven or over heated beyond the LEDs specifications?

 

Q- What cold condition start up method does the driver use –if in use in cold conditions? Has the product been thermally tested?

 

If the product is for cold environmental use, it may need a driver that employs a slow current rise on start up - to avoid rapid thermal shock which reduces the LED life span

 

Q- Are the LEDs LM80 tested?

 

LM80 testing applies to the electrical optical performance/reliability of the LED component – not the finished product. If the thermal /electrical/optical management of the finished design does match the conditions used in the LM80 report, the LM80 data will not be a useful indication of performance or reliability of the complete product.

 

Only by checking the LEDs working conditions, when working within the product, can we compare the LM80 prediction conditions with the actual working conditions used. The product’s intended working environment has to be taken into account as well.

 

LM80 test and LED data sheets are useful to engineers for checking the validity of the claims on product samples and give some indication of LED component quality to the consumer.

 

Q -Is the product LM79 tested?

 

LM79 testing looks at the complete design/performance of the luminaire – looking at total system efficacy and light output after driver/optical/thermal losses are taken into account.

 

Not all products come with LM79 test.

 

Many products use LM80 testing in conjunction with comparison to actual LED working conditions. 

 

For new products on the market which have not been in service for 50,000Hrs LM79 tests simulate product ageing to provide a guide or prediction to the future performance.

 

Products already on the market, which come with case studies are useful for confirming the accuracy of the products specification /IES files /reliability statements.

 

 

LED Bin selection

 

When LEDs are manufactured, they are sorted in to differing quality groups known as bin selections.

LED bin selection can decide/alter the colour, efficiency, CRI, voltage and current of the LED used. To the average customer different LED selections may look the same, until the luminaire is electrical and photometricaly tested or they start to depreciate before their expected time.

 

Example: on a typical LED data sheet, we see the Luminous flux Bin selections – E.G. the luminaire manufacturer can choose from code A/B/C/D which varies from 60 Lm to 80 Lm per LED using a cheaper selection can lower the products light output by 25%.

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Replacing a designs high bin selection with a lower light output bin selection would shorten the time the product takes to reach the L70 depreciation point.

 

With bin selection, a manufacturer can choose to use the best high efficiency/ high CRI index LEDs with a particular set of electrical/photometric characteristics for the product.

 

However, they can use the good bin selection for the sample/prototype and then use the cheaper one for the production run – this can result in a product which is less efficient/reliable or unfit for purpose.

 

Sometimes manufacturers may run out of LED stock and use inferior LEDs to replace them – having a UK based quality control monitoring system can ensure consistent product quality.

 

The average UK customer does not have the facilities to check if the products are consistent with the origin specifications and test reports, or test that the thermal management of the product does not cause problems.

 

Luminaire specification

 

The market has seen some manufacturers which quote the LED specification data as the product specification, quoting the LEDs efficiency as being the luminaires. This is misleading as the final system incurs light output losses through issues such as thermal management/LED bin selection /diffuser loss /differences in drive current/input voltage /whether the LED is running from DC or is pulse driven.

 

A light plan designer could assume the product will work fine in an ambient air temperature of 35C however, the internal air temperature of an enclosed retrofit fixture will be higher than the external ambient temperature. The manufacturer/seller could have quoted the Ta of the driver not aware that the internal air temperature is higher than the external ambient as the sales staff are not technically trained to be aware of this.

 

As a result, the market has seen many failures of retrofit products and replacement lamps, where the internal air temperatures are up to 15C-20C higher than ambient – causing the LED and driver to fail if the given Ta rating of the luminaire, not driver, was not correct.

 

Always ask the manufacturer if the light output and Ta specifications are for the finished product and check it against the highest onsite temperature in the lamps location -expected on the hottest day of the year.

 

Some LED products can fail where the driver is mounted too close to the LED causing heat transference between the driver and LED array, and where there are multiple LED arrays wired in parallel. A heat imbalance of one array string can alter the electrical characteristics and cause it to draw more current on one array string than others, this thermally induced current distribution imbalance can lead to a cascade failure where the LED string get burned out one by one. We have seen this with many LED tubes/panels in the past

 

In the UK, the mains voltage can vary. Products that are bench tested at an ideal 230V 25C environment can fail/overheat when working at 180V /260V at higher internal air temperatures. Dirty environments which impede the efficiency of the luminaires heatsink operation can also contribute to pushing the luminaire beyond its specifications, this is why MG LITES check our products thermal/electrical /photometric performance at differing mains voltages, as found on sites in the UK to ensure the product is fit for it’s particular purpose.

 

If your installation site has high surge levels and voltage drops/interruptions and/or high or low temperature environment or/and a high dust/dirt level, it is recommend that you seek professional advice before commencing – as these conditions can combine to cause a potential onsite problem. These are the conditions in which many kit built, not fully certified luminaries fail du