13CommentsJoined October 15th, 2015

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• Yawn, this is getting so old!!! If you cannot admit that an LED which converts 3 times as much of its input power into light compared to an incandescent lamp is wasting a smaller percentage of its power input as heat then it is pointless to continue. For me, 85% is significantly less than 95% - it is about 10.5% less (to one decimal place). Try taking a 10.5% cut in salary and see how you feel about it!!

• Right, this is getting really silly.Point one - we BOTH agree that LEDs are more efficient at producing visible light than other forms of artificial illumination.Point two - we BOTH agree that the real economy with LEDs is the relatively low power input for light output compared to other lighting..Point three - we disagree on heat output, I consider that wasting a smaller PERCENTAGE of power as heat represents increased efficiency. You repeatedly tell me that the figures are almost the same but they are not the same. Remember that we want more efficient lights, and to my mind a light that converts 15% of power consumed into light is 3 times as efficient as a light that only converts 5%. Please tell me how it is misleading to state a fact - LEDs are more efficient because they convert a ...

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Right, this is getting really silly.Point one - we BOTH agree that LEDs are more efficient at producing visible light than other forms of artificial illumination.Point two - we BOTH agree that the real economy with LEDs is the relatively low power input for light output compared to other lighting..Point three - we disagree on heat output, I consider that wasting a smaller PERCENTAGE of power as heat represents increased efficiency. You repeatedly tell me that the figures are almost the same but they are not the same. Remember that we want more efficient lights, and to my mind a light that converts 15% of power consumed into light is 3 times as efficient as a light that only converts 5%. Please tell me how it is misleading to state a fact - LEDs are more efficient because they convert a higher percentage of power consumed into visible light. Please also explain to me how it is wrong to say that LEDs dissipate a lower proportion of the electrical energy as heat when this is a known and published fact.

• I refer you to my earlier comment repeated below:A typical incandescent bulb converts energy into IR, heat and light - with only about 5% ending up as light. The IR ends up as heat (won't go into the physics here), so 95% of the input energy ends up as heat and only 5% as light in the visible spectrum. LEDs (current generation as used for lighting) convert around 15% as visible light and 85% as heat.Taking a 60W incandescent bulb as an example, for comparable light output a CFL generates about 9 times as much heat as an LED, and an incandescent generates about 25 times as much heat.However, since I am only a degree qualified electrical engineer with 40+ years of experience I am probably totally wrong.

I can see you are a pedant so I must choose my words with extreme care. In terms of efficiency as a source of light (and this is the reason most people buy lamps) LEDs outperform incandescent and fluorescent lighting. Most people choose their lighting to get the highest light levels per watt of input power and although LEDs do dissipate a relatively high amount of power in as heat, for comparative light outputs they are much more efficient than their commercially available competitors. The figure of 85% for LEDs is a typical figure - as technology improves this will reduce. You can't improve on a hot bit of wire so incandescent lighting will soon be relegated to the annals of history. Fluorescent are more efficient than incandescent, but have high startup power consumption and a signifi...

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I can see you are a pedant so I must choose my words with extreme care. In terms of efficiency as a source of light (and this is the reason most people buy lamps) LEDs outperform incandescent and fluorescent lighting. Most people choose their lighting to get the highest light levels per watt of input power and although LEDs do dissipate a relatively high amount of power in as heat, for comparative light outputs they are much more efficient than their commercially available competitors. The figure of 85% for LEDs is a typical figure - as technology improves this will reduce. You can't improve on a hot bit of wire so incandescent lighting will soon be relegated to the annals of history. Fluorescent are more efficient than incandescent, but have high startup power consumption and a significant delay in reaching full light output. Taking all factors into consideration LED lighting comes out on top for the majority of applications - mainly due to their higher lumen output per input watt.There's no such thing as a free lunch - all forms of lighting also emit heat (all energy reduces to heat eventually) so it is always sensible to consider this and protect surfaces or install appropriate heatsinks when installing any form of lighting.

• Sorry, I disagree. A typical incandescent bulb converts energy into IR, heat and light - with only about 5% ending up as light. The IR ends up as heat (won't go into the physics here), so 95% of the input energy ends up as heat and only 5% as light in the visible spectrum. LEDs (current generation as used for lighting) convert around 15% as visible light and 85% as heat. Taking a 60W incandescent bulb as an example, for comparable light output a CFL generates about 9 times as much heat as an LED, and an incandescent generates about 25 times as much heat.

• Wiring in series is a big no-no for several reasons:1. Current consumption for each LED will vary slightly - wiring in series will mean than the light output will vary for each strip.2. In a series circuit, if one strip fails open circuit you lose all the lights - think about Christmas tree lights and the hassle finding the one blown bulb!3. If any LED fails short circuit, you could potentially short out the power supply . This could either blow up the LEDs between the short and the power supply, or blow up the power supply as well.

Good idea - there are commercially available kits available to replace the fluorescent tray in light fittings with LED units but its much cheaper to do it yourself. If your strip out the ballasts from the fittings you can incorporate a 12v power supply in the fitting to make a self contained mains powered LED fitting from an existing fluorescent.

LEDs - like all forms of lighting - emit heat as well as light. They are just more efficient than other forms of light and dissipate a lower proportion of the electrical energy as heat.

all metals suffer from thermal expansion and aluminium has a coefficient about 50% larger than copper, so this would tend to have more of an effect in loosening screw terminations for large temperature fluctuations - which is the main cause of electrical fires (high resistance joints causing localised overheating and arcing). Aluminium oxidises rapidly in free air and forms a very thin layer (a few nanometres thick) which protects the surface and limits further corrosion. This is easily penetrated when connections are made so it doesn't really affect things. Copper oxidises much slower and the oxides are semiconductors - but similarly the act of terminating is usually enough to break through any oxide layer and ensure a good electrical connection. Always helps to clean back to bright me...

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all metals suffer from thermal expansion and aluminium has a coefficient about 50% larger than copper, so this would tend to have more of an effect in loosening screw terminations for large temperature fluctuations - which is the main cause of electrical fires (high resistance joints causing localised overheating and arcing). Aluminium oxidises rapidly in free air and forms a very thin layer (a few nanometres thick) which protects the surface and limits further corrosion. This is easily penetrated when connections are made so it doesn't really affect things. Copper oxidises much slower and the oxides are semiconductors - but similarly the act of terminating is usually enough to break through any oxide layer and ensure a good electrical connection. Always helps to clean back to bright metal before making a connection though Both metals exhibit further corrosion in the presence of acids and bases. Although aluminium is not such a good electrical conductor, it is mainly used because it is much lighter than copper (less than a third of the density).I personally check all electrical connections (outlets, switches, junction boxes) in my home every couple of years - its surprising how much they can loosen through usage and general vibration as well as thermal expansion/contraction.