More thoughts on the Eaton MEM BC3, CFLs and Power Factor

Light bulbs

UPDATE: See this more recent post for information and photos of how to get a 2-pin bulb to fit in a BC3 fitting.

BC3 reactions

The post looking at the Eaton MEM BC3 system, a couple of months ago, has become something of a reference for UK householders and renters trying to work out why they can’t fit a normal 2-pin bayonet compact fluorescent (or other bulb) in the light fittings of their new house or flat – or so I assume from some of the search strings in the server logs.

Some comments from readers highlight the frustration and inconvenience caused by the 3-pin system – and in these cases it’s people trying to use CFLs in the fittings. They’re trying to be energy-efficient, trying to comply with government advice indeed, yet a combination of ill-thought-out regulations and a razor-blade-style commercial lock-in architecture of control is preventing their success. As an example of ‘reducing the environmental impact of products by using design to change user behaviour‘, the BC3 seems to be a poorly thought-out initiative.

MEM BC3 compared with standard 2-pin bayonet CFL

Increasing CFL uptake

Elsewhere, on the subject of CFLs, Duncan Drennan of The Art of Engineering blog has a very informative post looking at aspects of the CFL argument, such as comparing colour rendering indices, which are less often addressed in media articles on the subject. As Duncan makes clear – even including a spreadsheet to calculate the savings – the monetary arguments in terms of electricity saved are probably a more direct way to persuade many people than using environmental arguments.

Duncan also mentions the higher-end CFLs such as the Osram Dulux Superstar (which has a quicker start-up time to full brightness than standard CFLs). Along with CFLs which are shaped more like conventional incandescent bulbs (such as the version of the Osram Duluxstar, third from left in the first photo below), or even with more interesting forms, such as the concepts by Dutch designer Jacob de Baan (second image below), these surely have the potential to convert more householders to CFLs: the standard 3 U-tube design is rather ugly.

Some types of CFL compared with a 150W incandescent
Bulbs by Jacob de Baan
Above: Some types of CFL (from left: Tesco Value, GE Elegance and Osram Duluxstar) lined up next to a burned-out incandescent bulb. Note that the Osram Duluxstar – basically a standard 3 U-tube CFL with a bulb-shaped cover – is taller than even the 150W incandescent, due to the space taken up by the ballast, and this extra length can be a problem when using CFLs in existing light fixtures, shades, etc. Some companies, such as Sylvania with its Mini-Lynx Ambience range, have addressed this by making CFLs with shorter tubes and ballast such that the whole thing is the same size as a standard incandescent bulb. Below: Three CFL concepts by Jacob de Baan. Apologies for the scan quality (the images are from The Eco-Design Handbook, 2004 edition, by Alastair Fuad-Luke).

Power Factor

A rarely mentioned issue with CFLs which I realised recently (courtesy of a letter by Andrew Porter in The Engineer, a UK journal), is that of power factor. Not having studied electricity generation for some time, this is something I’d shoved to the back of my mind, but essentially it results from the phase shift between voltage and current caused by a reactive (capactive or inductive) load as opposed to a purely reactive one, and means that the actual power supplied by the power station (in volt-amps) will be greater than that indicated by simply looking at the wattage (in watts), where reactive loads are involved.

A normal incandescent filament bulb is an almost entirely resistive load, and the voltage and current will be in phase (hence a power factor of 1). But a CFL – with a significant proportion of capacitive load due to the ballast – will have a much lower power factor, perhaps only 0.5. This means that a ’15W’ CFL actually requires 30VA from the power station – which the private customer will not pay for directly, since home electricity meters only measure watts, but it is still equivalent to needing to supply double the power. That increase in necessary generation can’t be ignored: the consumer will pay for it one way or another.

Rod Elliott has a detailed examination of why the power factor should certainly be taken into account when looking at CFLs in a policy context and it’s very much worth reading for a better understanding of the issue. While fluorescent lighting ballasts with high power factors (0.95+) are available (in industrial situations, a large customer will often have to pay for the actual VA drawn by large reactive loads, such as motors), they are unlikely to be incorporated any time soon into mass-produced cheap CFLs. Elliott suggests that because fluorescent lighting is so often left on continuously (partly because of the belief that it will last longer if not switched on-and-off), in conjunction with the power factor issue, mass adoption of CFLs may actually increase the electricity used.

I don’t know to what extent policy-makers have taken the power factors of cheap CFLs into account when planning mass conversion initiatives, but in the long run, it would seem that LED home lighting (without a power factor issue), perhaps with DC ring-mains to prevent the need for multiple transformer/rectifiers, is a better solution than total adoption of CFLs.


  1. Thanks Dan 😉

    Valid point you have about power factor. Just remember that a low PF does not impact on the actual power consumed, but it does reduce the efficiency of power generation and distribution. Power utilities do plenty to make sure that the power grids PF is close to unity to save them money.

    The harmonics generated and the interference they can cause may be a bigger issue than the power factor ( It is an issue with just about all modern electronic equipment (due to the widespread use of power electronics), although a lot of higher powered items tend to have PF correction built in these days (I think??)

  2. Barry Woodside

    The comment “it would seem that LED home lighting (without a power factor issue)” seems to forget that these usually need a transformer/rectifier/capacitor, or more commonly these days, a switched mode power supply, supplying a constant current. Both have PF “issues”.
    In the EU, equipment over 25W require PFC.

  3. Emma H

    As a tennant I have just realised that it’s going to cost me at lkast £30 to replace the MEM 3 pin bulbs in my hallway. I don’t actually think they even last that long!!! We’ve been here 3 years from new, and already last year had to replace the bulbs with some that the builders left for us. They just suddenly start to fade! It’s ridiculous, these bulbs should be widely available and much cheaper if we are forced to have to use them.

  4. A quick note regarding the article covering the use of fluorescent lighting, notably the issue of Power Factor, reference my article in the magazine the Engineer. I can confirm that further work has been conducted on this particular issue. As a consequence, there are two new items that I can add to further prove that the Compact Fluorescent lamp is not the good idea that so many assume. These elements include the announcement made by General Electric in the USA that they have developed an incandescent lamp that is as efficient as a fluorescent lamp, without the problems of poor power factor, poor light quality, long start times, the inability to use dimmer switches, etc.

    Note: In the UK, when the efficiency comparison was made between incandescent lamps and fluorescent lamps, this was comparing the very basic, cheapest incandescent lamps, not the more efficient halogen lamps, the latter being readily available. Therefore, the indication that a 20W fluorsecent light bulb replacement is quivalent to a 100W incandescent lamp is only true when comparing with the very basic incandescent lamp.

    The other news is that of a better method of producing white Light Emitting Diodes that are significantly better than existing devices, in addition to offering a significantly longer life, that is 100,000 hours. The process involves better precision in the manufacture of the LED at the semiconductor level, so that about four times more of the available light emitting parts can be used. This, in part, is driven by the desire to have more reliable back lighting for Liquid Crystal Displays as used on computer monitors and television screens, rather than the present life limited Cold Cathode back light, Cold Cathode effectively being another form of fluorescent lighting.

    Finally, the other area where LEDs are being introducing is for automotice lighting where, for example, many new cars are using Red LEDs for the rear lights and brake lights, orange for indicators, etc. However, Hella, in Germany, are producing the first white LED headlamps for cars, where the challenge had been to create a light source comparable with a 65W halogen lamp.

  5. Rob

    Just spent 79p per fitting replacing the lampholders in a brand new house as nowhere local sells BC3 lamps, and £9 each online as opposed to 49p for Phillips CFls in Homebase: I ask you??!

  6. michael

    I HATE these 3 pin bulbs, total B&ll&&^t we are forced to use these in rented accommodation in new builds and now the bulbs are not available. Sure, online, but must I really take a day off from work to change a light bulb, so that i can stay home and receive the delivery. Is there an adapter? I cant change the fitting as it is rented accom. What a total disaster this is. Central govt strikes again.

  7. Rich

    Changing the fittings sounds the most economical way forward espec as I’ve got a stock of conventional CFIs in the cupboard. How easy is this to do?

  8. Dan

    Hi Rich,

    It’s trivially easy to do – and the standard 2-pin bayonet fittings can often be had for 99p or so in DIY stores. But – a) make sure the power’s off – really sure! (it doesn’t matter which way round the live and neutral wires are in the fitting, so don’t worry about that) and b) be aware that it _might_ actually be illegal to do this work yourself given the regulations as they are now ( ), depending on what room you do it in. Presumably if your house/flat came with the MEM BC3 sockets, it was to meet the building regs ( ) so I don’t know what a surveyor would say when you come to sell.

    It’s actually quite easy with a pair of pliers to bend the BC3 fittings to allow a standard 2-pin bayonet bulb to fit – at some point I’ll put some photos on the blog of how to do it – but again, if you do this, make damn sure the electricity’s switched off first and there’s no-one around who might switch it on while you’re doing it.

    The whole system is ridiculous and it really needs to be shown up as the shambles it is.

  9. I have just moved into a new house and all of the ceiling light sockets are BC3 fitting. As far as I can tell, Mem only make four bulbs, two colours, warm and cool white and 15w or 20w.

    My hobby is photography and I use a room to print my photos using a high quality ink jet printer and a colour calibrated computer screen. Under these ‘coloured’ lights the prints and the monitor look wrong, so I bought a 65k daylight bulb. It is a two pin fitting and now I cannot use it. We also cannot fit the more attractive ‘traditional’ shaped low energy bulbs. The whole thing is a total mess in my opinion.

  10. nn yadav

    from where i should get CFL with 0.95 pf. pl send me address and cost.

    nn yadav


    hi all as to the BC-3 light fixture’s they nothing but a complete rip off.. moved into brand new house only 3months ago 2 of these £12+ long lasting bull sh*t bulbs have blown in less than a month..
    so here’s how daddy cool who aint no fool.. done a 5min modification on the BC-3 light fixture’s to take the normal 2 pin light bulb as well as the 3 pin rip off bulbs

    first off if ya completely clueless about wireing then its best you dont have ago yaself.. either buy a book on home electric’s and have quick read on the subject you’ll soon pick it up just as easy as putting a plug on ya toaster .. but if ya a politition or something its best you pay the £12 as you prob still dont know how to tie ya own shoe laces yet and have to pay someone to do them for you..

    make the 12 o’clock slot in the BC-3 fixture about 2mm wider i used a dremmel but a pair of cutters will do the job just as well then on the 6 o’clock slot where the blub pin holds in place cut the slot so the blub pin can twist about 2mm further round.. and bobs ya uncle ya just saved ya self from being forced into buying a poor quality light bulb that costs £12+ in which you’ve prob spent £20 in petrol driving round tryin to find a store that sells the useless things.. save the planet ??? i ask you!! as for having to be qualified to connect 2 wires in a light fixture.. maybe those who make these rules & regs still need mummy to wipe their back sides every day in life.. or will we all have to be qualifed to use the toilet sometime in the near future..

  12. Dave Collins

    My new(ish) flat has these BC3 fittings in the two bedrooms but standard 2-pin everywhere else.

    I simply changed these bulb holders, and I believe that it was legal under Part-P because I was simply ‘replacing a fitting’.

    If I remember correctly, under Part-P you are allowed to change fittings (bulb holders, switches, sockets etc), and even add a spur to an existing ring main as long as it’s not in certain areas (zones) of the kitchen and bathroom.

    As for the CFLs themselves, I cannot stand them, I really tried but the main problems for me were:

    1) Startup time, in the 21st century I expect my light to come on instantly.

    2) Colour temp – have tried a number of different bulbs and they’re all horrible.

    3) They interfere with my Sky signal.

    4) They interfere with my X10 system.

    5) They interfere with my IR remotes.

    6) They don’t last anywhere near as long as promised.

    Efficency (%) = ( Useful-Energy-Out / Energy In ) x 100

    Therefore incandescent bulbs are 100% efficient! I like heat, it prevents me from dying of hypothermia!!

  13. Soylent

    You’re wrong.

    Reactive power eats up transmission capacity but since reactive power will simply oscillate back and forth between you and the power company without doing work you’re only incuring line-loss which is almost negligible.

  14. Bernie

    These MEM BC3 lights are a con ! In just over 2 years, 3 which were new to start with (new build flat), have already blown on me, the last one tripping the rcd in the process !
    I have a Philips which has now followed me for several years residing and still giving good light in the bedroom.
    Off goes another one of those BC3 fittings, in goes a normal one and a “decent” low energy bulb at a fraction of the price !

  15. Sparrow

    Another solution which will work for some circumstances. If the kitchen and bathroom (say) are fitted with 2D enclosed fittings (not especially attractive but a good light output)then that will probably be enough to satisfy the building regs requirements for dedicated low energy fittings.

  16. Sparrow

    Another solution which will work for some circumstances. If the kitchen and bathroom (say) are fitted with 2D enclosed fittings (not especially attractive but a good light output) then that will probably be enough to satisfy the building regs requirements for dedicated low energy fittings.

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