How to choose LED light bulbs?

Discussion in 'Electricians' Talk' started by LeoLeo, Mar 16, 2016.

  1. LeoLeo

    LeoLeo New Member

    Now LED bulbs are finally getting there. A couple of years ago they would cost you an arm and a leg if you change all your bulbs at home (an average house in Britain has ~25 bulbs) into LED ones but now you can get a pretty decent one for a few quids. This is when their electricity bill cutting starts to make sense as you can get the upfront cost back roughly within half a year. All the left in their claimed 10+ years lifetime would then be pure savings.

    It can however be quite a headache when it comes to choosing an LED bulb (yes, if you search “LED bulb” on Amazon you get seven hundred thousand plus results). Well, they all say that they are super energy efficient, offer brilliant light and last for almost forever, which is simply not the case. Although there is loads of information on the web trying to advise how to make that choice, when you start to get into the detailed specs, jargons like the CCT and CRI do not always make a lot of sense. Even when you think you have figured out all the tricks and finally installed a batch for your living room, it is not unusual to “just not feel the same as before”.

    What I will be discussing here is an approach to choose an LED bulb simply by its appearance, without having to work out the specs. It’s not going to be as precise as digging into the datasheet but it probably takes 1% of the time needed and filter out 99% of those not worth spending time on. Also I will not be covering things like the base or shape of the lamp, e.g. E27 or E14 or GU10, since there is already plenty out there.

    A somewhat popular type of LED bulb that you should definitely not touch is those consisting of lots of small “lamps” such as
    bad 1.jpg
    These small “lamps” are LEDs of the last century. They are simply neither bright nor efficient enough.

    More commonly seen are bulbs with bare yellow chips exposed without any lens or diffuser (normally translucent plastic that spreads out the light) on them, such as
    bad 2.jpg
    Stay away from this type because it can’t deliver the light to where a proper bulb should do, and it tends to glare badly – the bulb shines too brightly but does not illuminate properly, if that makes sense. More importantly, these useful optical components are omitted mainly due to cost saving. Therefore the other parts used in such a bulb would unlikely be of high quality. You may end up with a third of the chips still working after a couple of weeks, or the whole thing just fails as the driver can’t cope with its working conditions.

    Taking this approach forward, it is fairly safe to judge the quality of an LED bulb by the complexity of its optical components, i.e. lenses and diffusers, which are the most visible. Normally a bulb with a thin and flat layer of diffuser as its only optical component tends to be cheap, and claims such as long lifetime on such LED bulbs would be very doubtful.

    A high quality LED bulb tends to have a large and robust piece of diffuser with a sophisticated shape, or in the case of directional lighting such as PAR lamps including GU10, a lens designed with a certain level of complexity. Here are some examples from Philips

    diffuser.png.jpg lens.png.jpg

    The diffuser and the lens direct and distribute the light to where it should go to optimize the illumination and minimize the glare. More importantly, as they are indeed a less essential part of the lamp (or of the datasheet), if the manufacturer decides to spend substantially on them they are more unlikely to compromise the quality on the more critical parts such as the LEDs and the driver.

    The most complex lens design is perhaps a “3D lens”, which enables smart distribution of the light within a limited space, making the bulb compatible for more luminaires. Here are some flagship products from Philips and Osram, the world’s top two lighting suppliers.

    3d lens 1.png.jpg 3d lens 2.png.jpg

    It is not surprising that products with sophisticated diffuser or lens tend to be more expensive. Here are a few on Amazon with 3D lenses

    Again, judging the quality of an LED bulb by the complexity of its optics is quite opportunistic and may not be accurate. But the approach is probably an optimal tradeoff between the time you want to spend in choosing a bulb and the risk of not getting your place lit up properly. After all, LEDs are the light source of this century.
    Ghost-1 and nffc like this.
  2. johnny1

    johnny1 Member

    just go to poundland ...

    entire house lit with 45 w of leds ...
  3. MGW

    MGW Screwfix Select

    The MR16 replacement, (they are often not MR16 as no reflector) has many fittings, I have GU10, G5.3, E14 and E27 in my house all with a 2 inch (16/8 inch). And I have found surface area is a big thing. Aim a GU10 at a white ceiling and it can do a great job as the area the light is reflected from is huge, stick a line of LED's in a translucent tube and they work better than with no diffuser. Again fit 10 x 2W GU10 or 2 x 10W GU10 and the results are very different.

    But the big thing is the lumen per watt. There are one or two with 120 lumen per watt, but in the main good quality lamps have 100 lumen per watt. Look at any package designed to replace a fluorescent and near every time it has 100 lumen per watt, look at DC lamps designed for caravans and again 100 lumen per watt.

    However look at the cheap rubbish aimed at replacing the tungsten bulb and we get 60 ~ 80 lumen per watt. Look at some of the fancy colour changing LED's and we are down to 30 lumen per watt.

    Point is we simply fail to look, the LED is a current device and some where we have to convert voltage to current regulation. It can be a resistor, a capacitor or a full blown PWM chip. I still think of PWM as being switched mode, why we changed the name I don't know.

    When replacing a CFL with a standard E27, or E14, or BA22d base to get a LED which preforms better is easy, the CFL was useless, however once you look at the larger folded fluorescent or simple fluorescent tube specially with a HF ballast the LED is only just better. We are looking at 95 lumen per watt v 100 lumen per watt and a life of 30,000 hours to 35,000 hours there is very little between the two types of lamp.

    Where the fluorescent fails is the spread of light. A 5 foot fluorescent tube is 58W and around 5600 lumen but an LED 5 foot tube may be just 24W and 2400 lumen and often we can get away with less light it is the spread we need specially in corridors. Also where to swap a lamp it needs two men and a cherry picker extending the life from 8 to 12 years is a huge saving in labour.

    In a bulb format the LED even at 60 lumen per watt is better than the CFL. But once you start to look at role out strips and fluorescent tube replacement then the LED has a long way to go. Over 20 years replace a HF fluorescent tube 3 times at £5 each or a pair of LED tubes twice at £18 each. So £15 compared with £72 I think I will stick with fluorescent even if only 95 lumen per watt instead of 100.
  4. madhatter1uk

    madhatter1uk Screwfix Select

    They're over rated and over sold. I wish manufacturers would just stop it. It's only the most expensive ones that give a light comparable to a traditional lamp.
  5. johnny1

    johnny1 Member

    Bah.. all very technical..

    I don't even bother turning the lights off now
    madhatter1uk likes this.
  6. LeoLeo

    LeoLeo New Member

    It's not going to be of great quality...
  7. LeoLeo

    LeoLeo New Member

    From ~2015 there are definitely good and affordable ones on the market.
  8. LeoLeo

    LeoLeo New Member

    Yes, lm/W, i.e. the efficacy is the key metric to benchmark one with another.
  9. johnny1

    johnny1 Member

    well they light the house perfectly in a warm white cost less than £20 for the entire house and have been in some 9 months...

    not had one fail ..

    and lets face it and put it into contex.. one old bedroom bulb used 60w ...
  10. madhatter1uk

    madhatter1uk Screwfix Select

    They're called lamps, bulbs grow in the ground.
    Phil Hyde, sparky Si-Fi and tore81 like this.
  11. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Good work my young padawan!
  12. MGW

    MGW Screwfix Select

    A lamp is the whole unit, which traditionally would be mounted on a spigot or a rise and fall so the oil could be put in and the wick trimmed without the need to stand on a ladder, as time progressed the oil and wick were replaced with gas and mantels, but still the whole unit is called a lamp so we need a different name for the components found inside a lamp. Since the original electric lamps had a bulbous unit which contained the parts which have a limited life then to name it after the shape makes sense. Call it a bulb or a tube it describes it well. The lighting industry has over the years kept the old names even when there is a new product to replace it, so the transformer replacement is called an electronic transformer, the ballast replacement is called a HF ballast as so to call the bulb replacement even if a folded tube fluorescent a bulb follows the lighting industries tradition.

    Where the problem arises is with the driver, the driver was a current limiting device used for air craft ground lights and LED's calling a voltage regulated unit a driver grates on me, as it means in real terms we have lost the name for a current regulated supply.

    I made the mistake early calling a bulb a lamp, I order a head lamp when the bulb went, I got everything but the bulb, serves me right for trying to be cleaver. It is easy to find out what they are called simply read the packet. I will admit with LED units where the driver and the LED is combined in one package then may be it could be called a lamp.

    But it is like the guy who says you can't have an earth electrode with a TN-C-S system, very true, but it does not mean you have to pull out the earth rod, it just simply changes name and becomes an extraneous-conductive-part. At the end of the day it does not matter what you call it as long as the person your talking to uses the same name. Send some one to get you a 10W LED lamp and he returns with a integral unit instead of a bulb to go inside the unit you already have then it's your fault for not using the common term for the item.
    LeoLeo likes this.
  13. madhatter1uk

    madhatter1uk Screwfix Select

    The common term for them in the industry is a lamp.
  14. madhatter1uk

    madhatter1uk Screwfix Select

    Maybe it's time to turn your bedside light off before the lamp burns out.
  15. LeoLeo

    LeoLeo New Member

    Great work! Simply Google Image "lamp" and "bulb" one could see what's the most common understanding of the terms. I won't confuse everyone further with "luminaire"...
  16. madhatter1uk

    madhatter1uk Screwfix Select

    Just because most people think it, doesn't make it correct.
  17. retiredsparks

    retiredsparks Super Member

    Leo leo....thanks for your info on bulbs.
    LeoLeo likes this.
  18. LeoLeo

    LeoLeo New Member

    You are more than welcome!
  19. LeoLeo

    LeoLeo New Member

    In this case understandable is more important than and may actually redefine correct.
  20. chippie244

    chippie244 Super Member

    In my industry it's called a bubble as is a spirit level.
    LeoLeo likes this.

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