We throw the spotlight on light bulbs
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020 7924 1421 - 07866 724718 - steve@swbishop.co.uk
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Confused about light bulbs?
We're here to enlighten you!
I had a great response to my plea for feedback and ideas for future Circuit Shorts
topics. Thanks for all the great ideas I will definitely be using some of them and please
keep them coming. This month's Circuit Shorts was the brilliant idea
of Ali from Suffolk. Thanks for your great idea, Ali, your "I'm Steve's Star of the Month"
badge is in the post.

As you probably know, shopping for light bulbs can be a nightmare. You can leave the
shop empty-handed and feeling as if you need a degree in electrical engineering. Believe
me, the myriad of choice confuses me sometimes! Hopefully this month's Circuit Shorts
will clear up some of the confusion and shed some light (see what I did there?) on the
many possibilities.
- Bulb cap types -
The most important (and occasionally forgotten) item to check when choosing a light bulb
is the fitting or cap required. With so many different light bulb fittings available it’s an easy
mistake to make. Above are some of the most common cap types available in the UK.
The most popular fitting in the UK is the screw cap, available in several sizes but the most
commonly used are:
• E27, also known as Edison Screw (ES); and
• E14, also know as Small Edison Screw (SES).
Another popular fitting is the bayonet cap, available in two sizes:
• B22, also known as Bayonet Cap (BC); and
• B15, also known as Small Bayonet Cap (SBC)
There are also specific caps like the GU10 for downlights or other special light
fittings. These were traditionally available only as a halogen bulb but LED variants are
now available, and finally low-voltage G4 and mains-powered G9 halogens. You will find a
link to a detailed sheet listing all the available cap fittings at the top of page 10.

- Different bulb types -
Halogen light bulbs
Halogen light bulbs are the perfect choice if you're looking for a more energy efficient bulb
but still want to enjoy the same quality of clear, warm and sparkling light that you are used
to. Designed to mimic bright sunlight, halogen light bulbs are filled with a mixture of argon
and halogen gas and have a tungsten filament. They are also made from a higher-grade
glass that can tolerate the extra-high temperatures they generate. They do cost more than
standard light bulbs of the same wattage, but they're 20% more efficient and last up to 3
times longer. They come in 2 versions: a mains voltage (240 volt) and a low voltage (12
volt), with the latter requiring a transformer. However, the EU plan to ban all halogen
bulbs as early as next year and replace them with more energy efficient models.
Pros
• Cheapest to buy of the 'New Era' technologies
• Familiar warm light
• Dimmable
• Same look and size as traditional incandescent bulbs
• Full brightness instantly
• Uses 2-25% less energy than incandescent bulbs
• Contains no harmful chemicals
Cons
• More expensive to run than other 'New Era' technologies
• Still inefficient (only 20% energy saving vs incandescent)
• Short lifetime (approx. 2,000 hours)

Energy Saving CFL (compact fluorescent light bulb)
CFLs need a little more energy when they are first turned on, but once the electricity starts
moving, CFLs use about 70% less energy than incandescent bulbs because they convert
more of the energy they use into light, instead of heat. They give off a bright white
light ideal for kitchens, but are also available in cool or warm light versions for use in other
rooms. If you use fluorescent bulbs, it’s important to remember that they contain mercury
(in miniscule quantities), so they must be recycled rather than thrown in the bin. Also
known as Compact Fluorescent Lamps (CFL), these are often referred to as 'energy
saving' bulbs.
Pros
• 70% energy saving over incandescent equivalent
• Low running costs
• Dimmable
• 10 x longer lifetime than incandescent bulbs (approx. 10,000 hours)
Cons
• Slightly harsher light than incandescent
• Can take up to 2 minutes to reach 100% brightness
• Most contain traces of mercury so require careful disposal
• Bulbs tend to be larger than the incandescent bulbs so may not be suitable for all
light fittings.

Incandescent/ traditional bulbs
Although, incandescent bulbs are still around today, their technology has been surpassed
by new CFL, LED, and other lights but they still offer a very practical lighting solution for
some commercial applications. The EU planned a progressive phase-out of incandescent
bulbs due to the fact that they are not energy efficient. However, some manufacturers and
retailers have found a loophole in the new rules and some incandescent light bulbs are still
available, marketed as "rough service" or "shock resistant" bulbs for industrial use
only. So, while incandescent lights might not be the most recent technology, they still have
some key advantages that make them useful for commercial lighting in certain situations.
Pros
• Work well for lighting small areas
• Cheap to produce means they’re cheap for the consumer.
• No toxic materials like mercury, making them safe to handle and to dispose of.
Cons
• Not very energy efficient, only 10% of the energy used goes to creating light. The
rest is lost to heat
• Don’t work well in large areas
• Lifespan has been surpassed by other lighting solutions

LED light bulbs
Without compromising quality, LED light bulbs offer unlimited lighting possibilities. They combine
state-of-the-art technology with familiar design as they are available in the all the same shapes as
classic bulbs.
The most efficient bulbs available, using around 90% less energy than incandescent bulbs,
LEDs (Light-Emitting Diodes) produce light through the use of semi-conductors. Unlike
previous forms of energy saving bulbs, like CFL, they instantly reach full brightness and
are available in dimmable versions.
Maintenance is also minimal - LED’s usually have an average life of anywhere from 35,000
to 200,000 hours. With average usage, LED's will last 15 to 20 years. Imagine not
changing a lamp for over 15 years! Compare this to the measly 1,000 hours that an
incandescent will burn. The upfront cost of purchasing LEDs is high compared with other
less efficient lighting technology but they’ve usually paid for themselves within a few years
thanks to energy savings. For more information on the benefits of LEDs, see our
previous Circuit Shorts here
Pros
• Ultra low running costs (90% energy saving)
• From 35,000 to 200,00 hours lifespan
• Full brightness instantly
• No harmful materials

• Familiar warm light
• Dimmable options available
Cons
• Not all equivalent wattages and shapes are available yet
• Most expensive of the new technologies
Did you know?
Although the LED itself runs at a low temperature, the electronic circuit inside the bulb will
heat up. A heat sink is put in place to keep the LED as cool as possible; the bulb will still
become hot to the touch but not nearly as hot as fluorescent, halogen or incandescent
bulbs.
- Other information -
Dimmable bulbs
It is important to remember that dimmers require dimmable bulbs, so keep this in mind
when you are choosing your bulb. In the past, older types of energy-saving bulb tended not
to be dimmable; however these have now been replaced with a new generation of non-
flicker models that are also dimmable. Halogen bulbs are generally easy to control with a
dimmer switch, however, not all LED lighting is designed to be dimmable, and using a non-
dimmable bulb with a dimmer switch can cause the bulb to not work properly or fail
completely. So if you want to buy a dimmable bulb, make sure you check the product
details to see if it will work with a dimmer. There are many benefits to using dimmable
LED’s over dimmable halogen bulbs. As well as using up to 90% less energy, dimmable
LED’s maintain their colour temperature and luminous efficacy unlike halogens which
perform differently when dimmed.

When using dimmable LED bulbs an LED compatible dimmer switch will also be required.
It may therefore be necessary to replace existing dimmer switches if it is currently used
with halogen or incandescent bulbs.
There are two main types of dimmer switch:
• Trailing Edge Dimmer Switches – Used with LED bulbs.
• Leading Edge Dimmer Switches – Used with halogen and incandescent bulbs.
Note: Dimmable LED bulbs can also be used with a standard on/off light switch if you do
not need to use them in a dimmable application.
Watts and lumens (brightness)
In the past, when nearly everyone filled their homes with incandescent bulbs, brightness
was measured in watts - which is actually a measure of power. Since the introduction of
energy-saving bulbs this is a less useful measure of brightness as new bulbs use a lot less
power to produce the same amount of light. So, instead, light output is measured in
lumens. The higher the number of lumens, the brighter the light.
Use this chart to see equivalent watt and lumen output for old-style incandescent and the
three-types of energy-saving bulbs (LEDs, halogens and CFLs).
As a rough guide, around 400 lumens would be suitable for a bed-sized table lamp,
whereas you might want between 1,500 and 3,000 lumens in total (from more than one
bulb) for a good-sized living room.

This month's light bulb moment is actually about light bulbs! (You couldn't make this stuff
up). As you all know, there are squillions of different bulbs out there and I might be
stating the obvious, but why not take the old light bulb, or even the box it came in, with
you? Even if you want to try something different, at least you will make sure you get the
right cap fitting. Whenever I install new lamps for a client I always leave one of the light
bulb boxes for reference. And if you have the old light bulb or box with you, the shop
assistant may be able to guide you in the right direction without you having to draw them a
diagram.

Please click here for a far more detailed information sheet listing all the available cap
fittings.
If you would like some advice on purchasing light bulbs or if you would like to make an
appointment for a free quotation on any of the services we provide (click here for more
details about the electrical services we can provide for you) then please contact me.
Next month: Our guide to downlights
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more information. To see our previous
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Steve Bishop is a qualified electrician
and a member of NAPIT. To see his
qualifications click here.

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Steve Bishop
Mob: 07866 724718
steve@swbishop.co.uk
www.swbishop.co.uk
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