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Choosing the Right Cap Fitting

Don’t Screw Around, we help you choose the right cap fitting 

Anyone looking to change their light fixtures has to think about more than their bill, or the ambience in a room. Practically, a bulb can’t just have a random stand-in – it needs one of the same size and design, which is dictated by the cap fitting. Buy the wrong replacement set, and you won’t be able to use it; therefore, choosing the right cap fitting is an essential part of your purchasing decision.

If you’re casting blindly for advice, let’s illuminate the paths to follow when an LED switch is waiting for the go-ahead…

Edison Screw (ES)

Thomas Edison is the grandfather of commercial electricity, having first patented the light bulb in the early 1900s. This cap was his preferred fitting method, consisting of a line of top-to-bottom screw grooves. It is used all over the world, primarily for main room fixtures, floor lamps and desk units.

Basically, it’s your standard bulb cap, with a diameter of 27mm. They’re often labelled E27 for the regular sized model, although other Edison Screw sizes exist for multi-headed lamps and large candle bulbs.

Small Edison Screw (SES)

 We just alluded to spins on the Edison mould, and the SES is one of them. At 14mm, it’s almost half the measurement of an ES, making it suitable for less intense light sources. By this, we’re referring to chandeliers, bedside lamps, and decorative bulbs that hang on a wall or furniture piece. Like its bigger relative, the SES screws into place with a steady motion of the hand.

Bayonet (BC)

It’s the easiest fitting solution, and that’s why it’s the most popular cap in the country! Bayonet fittings are distinguished by two pins on either side of the bulb. Once guided into the socket, they’re twisted to fit corresponding holes – a little pressure on the head of the bulb will release it. They hit the 22mm mark, and tend to come with an extra pin for specialised industrial lamps. The lion’s share of UK mains lighting units relies on the BC blueprint.

Capsule (G9)

Halogen bulbs sap a lot of energy from our domestic or commercial power source. They’re a prime target of LEDs, thanks to the latter’s significant reduction of electricity cost for the same lumens count (more of which you can learn about here [LINK to lumens/wattage blog]). When you’re switching from a halogen-intensive space, you’ll likely have to buy a Capsule fitting, which is characterised by a pair of looped pins 9mm apart from the base.

Spotlight (MR16) with GU10 and GX5.3 base

MR16 is the physical envelope size of the lamp, are larger than our previous category, very commonly used and come in a variety of different base fittings. The most common types encountered are GU10 bases, and come in a 2-pin ‘twist/lock’ fitting for direct 240v operation from the mains power supply. GX5.3 base types are physically similar but with thinner ‘push/pull’ pins and are low voltage, 12volts, powered from a companion transformer.

They can be used for domestic interiors too, like the kitchen or lounge, but they are quite intense, so we suggest dimming your LED equivalent when it’s beaming above your guests or family.

When choosing the right cap fitting, there aren’t any ifs or buts surrounding the working feasibility of your LEDs… It’s nice to know that, with our help, you’ll get the exact, relevant bulb caps for any switchover you have in mind! Contact the Well Lit team if you’re still in a muddle, before that next great lighting purchase sparks to life…

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