LED Questions & Answers

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‘Can I save energy and money by changing to LEDs?’

It all depends on your existing installation. The simplest way to find out is to ask the Mikhno Group team for a lighting energy survey. They will tell you where you can save energy and provide a Return on Investment (ROI) spreadsheet showing costs and payback periods. They can also advise on retrofit lamps.

‘LEDs are the most efficient light source available… aren’t they?’

Unfortunately, there is not a simple yes/no answer to this question. The main reason is that LED fittings and retrofits vary enormously in quality. The LED itself, also known as a chip or dye, can be very efficient. However, when it warms up and is inside a light fitting, the output will be considerably less. Some good LEDs can exceed the efficiency of T8 fluorescent, whereas some low wattage retrofits we have seen were worse than T/H in terms of the amount of light per watt they emitted. LEDs are very directional and the illumination directly under the fitting can be more than fluorescent, but you need to consider the total installation to make a fair judgement. 

‘Is an LED downlight more efficient than a compact fluorescent one?’

Normally, the answer is YES but you must make sure that you achieve similar levels of delivered light. As a general rule, CFL downlights where the lamps are horizontal emit more light than the same downlight with vertical mounted lamps. Also, high wattage CFL downlights generally emit more light per watt than low power ones, e.g. 2 x 24W compared with a single 18W. If the downlights are for a corridor, consider the distance between the fittings. LED downlights often give a narrower beam than its equivalent CFL, so you might get a less uniform appearance on the walls and floor. 

‘How do I choose a good quality LED?’ 

The quality of LEDs and fittings varies enormously. As a rule, better quality LEDs will have longer life, higher light output, better colour rendering and lower energy 
consumption. Mikhno Group staff are trained to advise clients on the quality of products available. There is often a choice of equipment available. Always read the data 
given in the literature carefully. If a particular aspect is important to you or your customer, read about it in more detail in this leaflet. 

‘How do I calculate how much a lamp costs to run in £ per year?’

The calculation is: Watts x electrical cost per kWh xburning hours per year /1000.

For this, you need to know three things: 

A) The wattage of the lamp (preferably including the gear losses if you know them, but just the lamp wattage will give you a good idea). 

B) The cost of electricity per kW/hour. A kW/hour is often called a unit of electricity. A typical figure might be 12p per unit but remember that 12p is £0.12 when you enter the figure in your calculation. 

C) The burning hours per year. A typical office is 3000 hours, dusk until dawn lighting is 4380 hours. 

As an example: 60W x£0.12 x3,000 hrs/1000 =£21.60

Note that occupancy sensors and dimming can also be used to save energy but it is harder to estimate actual energy savings compared with a simple ‘watts used’ 
calculation. 

‘Can Mikhno Group staff do the calculations for me?’

Yes, our staff would be pleased to calculate the energy savings for you. The Mikhno Group have dedicated teams who will complete full ROI documents that will include energy saved and installation costs. 

‘What does rated life mean?’ 

This is an average figure giving the operating hours when 50% of a batch of lamps/LEDs has failed. Note that after this period, the light output from the still unctioning 
lamps/LEDs will also be lower. See page 17 for more information.

‘Why does the back of the LED feel hot?’

LEDs produce their heat over a very small area (often less than 1mm) and this heat needs to be conducted away as quickly and uniformly as possible. The LED fitting 
feels hot because it is usually smaller than its equivalent using another light source. Good quality fittings will have metal heat sinks and fins to dissipate the heat. 

‘How do I know if I am buying a cool or warm appearance LED?’ 

The simplest way is to look on the packaging or luminaire label and look for a figure like 2700K, 3000K, etc. The lower the figure, the warmer the appearance. Cool LEDs will be in the range of 4500K to 6500K, maybe even higher. Alternatively, switch on the fitting and look at it in daylight. Warm LEDs will be slightly yellow or orange in appearance. 

‘How often do I need to clean an LED fitting?’ 

A lot of users clean the fitting at the same time as they replace the lamp. Since LEDs have a much longer life, cleaning is not required often. In clean environments like offices, this may not be a problem especially since most LED fittings do not have reflectors that collect dust. In factories there can be a build up of dust and it is recommended to use a sealed fitting so that only the outside needs to be cleaned. 

Remember that the latest edition of BS7671 requires that all electrical equipment is inspected every six years, or sooner. This could be used as an occasion to also 
clean the luminaire.

‘If I am offered a guarantee, what questions should I ask?’

Firstly, the guarantee should cover complete failure of the luminaire within its rated life. 

  • You should check what the rated life is. 
  • Suppliers will normally pay a proportion of the replacement cost equal to the hours operated up to failure. 
  • Ask if the guarantee covers failure of just some of the LEDs in the luminaire. 
  • Luminaires with multiple LEDs should also be covered for the failure of some of the individual chips. This will lead to a reduction of light output or, in the case of RGB units, imperfect colour changing. 
  • Also ask if the guarantee covers light loss over time
  • Ask what the guarantee will cover if the output is less than stated? 
  • ‘What is the life of an LED driver?’ 

Typically drivers are guaranteed for 50,000 operating hours. This is more than 12 years for most installations.

‘Where can I get independent advice on LEDs?’

Often there are several products available that can do a similar job. Mikhno Group staff can explain the differences in the range of our quality products. They are there to help.