Q&A: Ask an expert

June 12th, 2014, Published in Articles: Vector


In this article, we talk to IESSA technical adviser Connie Jonker about LEDs and find out whether cost-benefit studies have been conducted on them; whether manufacturers’ temperature-rise and lifetime claims hold truth, and whether we should be concerned about some imported LEDs, among others.

Connie Jonker

Connie Jonker

Are there cost-benefit studies available on these lighting sources?

Cost benefits should be conducted on each installation. These would have to be based on factors such as lamp and energy cost, colour characteristics, expected lamp life, labour cost of service and maintenance.

Does anyone test the temperature-rise claims made by manufacturers?

In most cases, the temperature-rise claims are applicable to the LED light source. The temperature characteristics when fitted into a luminaire are affected significantly by the LED driver current, dissipation of heat in the luminaire due to convection, radiation or conduction. Each case must be evaluated to establish whether the LED temperature is within the manufacturer’s recommended value. Rigorous testing of the luminaire/LED combination is therefore strongly recommended.

Are colour-fading claims made by manufacturers realistic?

This is anybody’s guess. One can assume that claims on products from reputable and well-known manufacturers can be taken to be reliable. The problem arises where products are branded with the distributor’s trade name. In these cases, it is advisable to ascertain the origin or to insist on proof of these claims by means of test reports from an independent test laboratory.

Are the luminaire or lamp lifetime claims made by manufacturers tested?

Lifetime testing is an expensive exercise and requires extensive test facilities. Usually, life testing is ongoing by the manufacturer, but can only cover a small percentage of production. Lifetime claims on LEDs are based mainly on estimates and experience of electronic component life. The availability of actual lifetime test results of 50 000 hours is unlikely. Such testing has certainly not been conducted locally.

Are the environmental effects of discarded CFLs and LEDs tested?

The disposal of lamps containing hazardous metals has been a matter of concern. It is everyone’s responsibility to ensure that disposal of hazardous waste is conducted as recommended. In the case of CFLs, the technical committee responsible for the compulsory specification insisted that CFLs distributed in South Africa comply with the 6000 hour lifetime requirement as specified in VC9091. This requirement was introduced to minimise the number of lamps to be disposed of. If, however, non-conforming lamps with short lifetimes are allowed to be imported, the amount of lamps to be disposed will escalate.

In addition, IESSA and major lamp manufacturers have come together to formulate plans and infrastructure required for the disposal of lamps. The appropriate government authority was approached with these proposals, but the response and lack of action indicate that this aspect appears not to be of high priority. Discussions on these issues are ongoing.

Is local industry manufacturing LEDs in significant volumes?

All LED chips are imported, but a fair amount of lamp and luminaire assembly takes place locally. These manufacturing processes are expanding rapidly. A fair number of reputable local lamp and luminaire manufacturers have transformed their product ranges to LED light sources as they became more suitable for use in general and in specialised lighting projects.

The introduction of LED luminaires in various applications has become viable due to the vast improvement in LED performance over the last decade.

As the local industry can only compete on an acceptable product quality basis, locally manufactured product is generally of good quality as manufacturers ensure that product design, photometric performance and thermal control receive the necessary attention to build reliability into their products.

Are concerns about some imported LEDs valid?

It is unfair to assume that Chinese imports are generally of substandard quality. However, the experiences that end-users have with lower-priced, imported LED products indicate that the quality levels do not meet claims and customer expectations. It is, however, unfortunate that no significant test data is available to confirm such perceived low quality. There is also no means to conduct significant local testing on LED product performance and life expectancy. Large-scale life testing of these products is a very lengthy and costly process and would not be viable for commercial test laboratories.

Is there a limit to the output power of LEDs?

The recent development of LED light sources has shown that the light output characteristics have increased rapidly and that the rate at which this is happening does not yet seem to be leveling out. This gives us reason to believe that, in view of energy-saving benefits, the transition to these new light sources may result in the phasing-out of many traditional light sources, provided that the initial cost of LED products is contained.

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