Lighting Q & As – answered by the Voltimum Lighting Expert Panel

Question: Why do 12V LED lamps interfere with digital radio signals?  My radio goes dead when the LED lights are switched on, so why do 12V LED lamps interfere with digital radio signals? Can anything be fitted to stop it?

Answer by OSRAM: This sounds like an EMC issue and could relate to the transformer or lamp itself.

Care should be taken regarding cable lengths.

Most manufacturers test their products and specify a maximum cable distance on the secondary side. This is for both voltage drop and EMC reasons.

Answer by The Lighting Industry Association (LIA): There are strict limits set on EMC for lighting products and most reputable suppliers test their products for compliance. The Lighting Industry Association (LIA) is aware of a number of reports of LEDs allegedly interfering with digital radio broadcasts and is in touch with both the BBC, which monitors this on behalf of the Government, and the EMCIA to establish just how bad the problem is.

As an aside, the LIA is conducting market surveillance on 2,000 LED retrofit lamps in its lab in Telford, and as an entirely non-scientific experiment, I took my digital radio into the room and actually received a better signal than I do at home.

Question: Is HID (discharge) lighting now effectively ‘dead’ for commercial and industrial applications?

Answer by Glassguard: HID lighting is absolutely NOT dead for commercial and industrial applications.

Metal halide technology has consistently improved, which has allowed significant benefits in both, increased lumens per watt and higher quality Colour Rendering Index (CRI). In addition, there is now a much greater choice available in lower wattage energy saving versions to replace older traditional 250W and 400W installations.

For example, a 400W sodium, mercury or metal halide lamp can now be replaced using a 320W metal halide, providing an instant energy saving of 20%. 250W versions can also be replaced using a 200W metal halide providing an identical saving.

To convert to lower wattage metal halide lamps, it will be necessary to change the control ballast inside the fixture and should be carried out by a qualified person before lamp installation. This type of upgrade can be very cost effective with a fast payback period as it negates the purchase of a complete new fixture.

Question: There are so many different types of LED light to choose from now, it’s almost impossible to know which to specify. What do you recommend I do?

Answer by Philips: The lack of standards has been a problem in making the right choice of LED lamp, but this is set to change dramatically soon, as standards are being set out.

These will demand a level playing field in terms of the ways in which LED information is set out, so that it will be much easier to compare different LED lamps and those from different manufacturers with respect to performance and standards compliance.

So the sort of confusion that is so common now will become less and less of a problem soon.

Question: What causes an LED GU 10 lamp to flicker?

Answer by OSRAM: Flashing is often associated with load issues, typically minimum load. Also deep dimming in particular can affect the operation of a lamp. Things may appear stable initially, but once dimming has been introduced to the equation, inconsistent operation can be seen.

Lamps may not be happy to switch on at low level, so the dimmer may have to be set at full output first.  Even when a dimmer is set to full output, some clipping of the sine wave can occur.

Another cause can be a capacitive charge can build up causing LEDs that have been switched off to flash momentarily.  Many of the latest generation of lamps have additional circuitry to prevent this from happening.

Question: Why have some LED GU10s been banned? LED is a new technology, so isn’t the EU trying to ban only old technology light sources?

Answer by General Lamps: The Energy Related Products Directive (ERPD) does not seek to discriminate between technologies, but sets increasing efficiency limits. These have had the effect of banning certain older technologies such as incandescent lamps.

The efficiency of LEDs can vary quite dramatically and it is simply a fact that the less efficient LED GU10s have been caught by this regulation.

The answer is in compliance with DIM 2 (Domestic Implementation Measure 2).

There has been an explosion of LED GU10 suppliers that have entered the market, the reason being that 77% of all retrofit GU10 LED lamps are GU10. These lamps are designed to replace 50W GU10 halogen lamps many of which do not meet the performance either mechanically or electrically of a 50W halogen GU10. Because of this it was decided that in the release of DIM 2, requirements should be set to ensure that any lamps that are put on the market meet criteria that will ensure they are directly equivalent to a halogen GU10.

Light output is being expressed in a different way. Traditionally, we have always associated wattage with light output, but with new technologies giving improved efficacies (the amount of light per watt of power that you get from a light source) we express light in terms of lumens – i.e. the amount of light a given source emits.

For an LED GU10 reflector lamp to be equivalent to a 50W halogen type, it has to hit the magic figure of 350 lumens, but in a 90 degree cone, which is the useful light that it gives out.

The following functionality criteria also have to be met.

1)    After 6000 hours burning there has to be 90% or greater lamps surviving.

2)    After 6000 hours burning the lumen decay must not have exceeded 20%, i.e. at 6000 hours, each lamp must not have lost more than 20% of its original light output

3)    Colour rendering CRI has to be greater than 80. CRI is the quality of light expressed on a scale of 1-100, 1 being monochromatic or a single colour, 100 being perfect or the light that we see when we are outdoors.

The following information now needs to be displayed on the lamp itself:

1)    Lumen output – lumens (lm)

2)    Colour temperature – kelvin (K)

3)    Beam angle – degrees

4)    All other safety information such as power and voltage

Information has to be displayed on packaging:

1)    Light output

2)    Lamp life

3)    Colour temperature

4)    Number of switching cycles before failure

5)    Warm up time to 60% of full light output

6)    A warning if the lamp cannot be dimmed

7)    Lamp dimensions

8)    Beam angle

9)    If the lamp is designed to replace a filament lamp and its dimensions differ, a drawing clearly showing the differences.

In addition to this, the equivalent filament lamp may be shown on the packaging as long as the light output is no lower than the equivalent that it is replacing. The same is applicable if you want to show the equivalent wattage to the filament source that the LED is replacing.

Question: How can I be sure that a particular dimmer will work with an LED lamp?

Answer by OSRAM: All companies are affected by compatibility issues, so check with the manufacturer. Many will have compatibility lists. Source components that have been designed to work together, typically ranges from the same manufacturer.

Dimming performance varies tremendously. Dimming can be non-linear, it varies depending on the generation of lamp, the wattage of the lamp and the quantity of lamps being dimmed together.

Load the dimmer up correctly. Speak to the manufacturer for loading advice. It may be necessary to de-rate the dimmer for an LED load.

Contractors are advised to source a lamp/dimmer/transformer and test the combination. It is virtually impossible for OEM manufacturers to test all combinations and keep this information up to date.

When I have been testing a batch of dimmers and transformers with our lamps, performance can vary significantly. Single lamps and multiple lamp scenarios have different dimming characteristics.  Also it is common that when a lamp generation is replaced, the new lamp may dim differently to the early generation. Our advice is to, where possible, test the lamp operation with the transformer and dimmer.

It is also a matter of educating our customers. Asking whether a dimmer is leading or trailing edge is not sufficient information.

Note that this is a rapidly moving market. A new generation of lamps can be brought out every six months or so – the situation may change. So far we have only talked about analogue phase cut dimming.  There are, however, new systems coming on to the market which are digital.  They ensure compatibility between lamp and dimmer, because they have been designed together to work as a system.  These typically use the back half of the sine wave to send information digitally from the dimmer to the lamp.  This would typically be on/off, and light level, but could include colour temp information for example, or send ‘group’ information.

Question: The Wiring Regulations provide voltage drop specifications, but how sensitive is LED lighting to voltage drop? For example, is the Wiring Regulations’ 3% limit flexible, or will this cause a problem with LEDs that work outside that parameter?

Answer by the ECA: LEDs are actually very tolerant of voltage changes and with high quality LEDs, this voltage drop issue is not actually a problem. However, it might be an issue with lower quality LED lamps.

In any case, the new standards that are coming in 2014 will make the LED voltage drop tolerance bands clear.

Note that a new Code of Practice for the Application of LED lighting systems will be published in 2014 by the Institution of Engineering and Technology (IET).

Question: In the newly published Part L Building Services Compliance Guide for non-domestic buildings, in the lighting section, Table 42 lists a much-extended range of different lighting control measures that contribute to meeting compliance. Which measures does the panel recommend as being the best ones to install (that are cost effective)?

Answer: There is no single right answer to this question. Zoning, daylight, non-daylight, frequency of occupation and other parameters are all important and consideration of them should help you make a start on selection of the right lighting system for a particular job.

So, to decide on the most appropriate and cost effective measures to meet compliance, it is important to zone the space to be lit. Key is that the space is split into zones where the elements such as available daylight, use types and occupancy rates are similar.

Another factor that should be built into the deciding of zones is the ability of the occupiers of a space to have control on light levels for their comfort. The Part L Building Compliance Guide supported by the BRE 498 Guide ‘Selecting Lighting Controls’ defines types of occupancy along with a range of recommended measures. These latter should be considered as minimum requirements for compliance and not necessarily best practice to achieve energy savings and occupancy comfort.  

There is an increased importance given to lighting controls in Part L 2013, where higher than previous weighting is given to controls as detailed in Table 42 of the Building Service Compliance Guide.

Question: There are so many different types of LED light to choose from now, it’s almost impossible to know which to specify. What do you recommend I do?

Answer by LPA Lighting: The best solution is to go to Society of Light & Lighting website where you will find a great download called: ‘A Guide to the Specification of LED Lighting Products 2012’. This very useful eight-page document, which is a joint publication of several leading organisations from the lighting world, tells you what to look for and what questions to ask. 

Here is the link to the website: www.cibse.org/content/AAA_Julie_Uploads/SLL_membership_forms_2013/LED%20Spec_2012V3.pdf

You can ask Liz questions online by going to www.voltimum.co.uk/ask - Select Lighting from the ‘Topic’ drop down menu ('Select a Value') and then LPA from the ‘Brand’ drop down menu.