This is a real conversation I had with a friend earlier this week:

Friend: “I want some of your fancy new LED light bulbs for my kitchen.”

Sarah: “What type of lamp?”

Friend: “Lamp? No, I need a light bulb”

Sarah: “The industry refers to them as lamps. It’s a generic term for a device that emits light, regardless of the technology. Whereas the ‘bulb’ in ‘light bulb’ refers to the partially vacuumed glass housing that contains the filament of an incandescent lamp.”

Friend: “OK…so can you get me 6 ‘lamps’ for my kitchen?” (delivered with a hint of sarcasm)

Sarah: “Sure, but what type of lamp?”

Friend: “I’m not following.”

Sarah: “Do you need a PAR lamp, A lamp, MR lamp, BR lamp? What type of base? And is the beam directional or omni-directional?

Friend: “Forget it.”

After that conversation, it occurred to me that the designations attributed to lamps–or light bulb nomenclature–are not part of the vernacular.

While I can’t possibly cover all lamp designations in today’s post, I’ll examine some of the more popular ones.

In simplistic terms, a lamp designation consists of a letter (or letters) followed by a number. For example, A19 or PAR30. The letter refers to the shape of the lamp, while the number refers to the approximate diameter of the lamp in eighths of an inch.

Figure 1: A-series, MR-series, BR-series, and PAR-series. Source: Isabelle’s Lighting

 

Figure 2: Lamp size reference. Source: Westinghouse Lighting

 

A-series

These lamps are known as the classic light bulb, as this pear-like shape bulb has been used since the early 20^th century. The most common A-series lamp is the A19, which is found wherever omnidirectional (equally in any direction) light up to a maximum of approximately 1000 lumens (ie. 75-Watt incandescent) is required.

MR-series

Multifaceted reflector. These lamps are used for low-light directional lighting up to a maximum of approximately 500 lumens (ie. 65-Watt halogen), and are most commonly used as display lighting in retail stores or in a residential application (track lighting).  The most common MR-series lamp is the MR16 (which is a derivative of the GU10, though they have different bases).

BR-series

Bulged Reflector. These lamps have a bulged reflector with a reflecting material that directs light. The reflector can be frosted, clear, or patterned – all of which transmit a different type of directional light – and tend to produce a more gradual fade at the outer limits of the beam spread than a PAR-series lamp. They come in a wide range of lumen output.

PAR-series

Parabolic Aluminized Reflector. These lamps have a hard glass, hermetically-sealed cover over the reflecting surface and include an optical lens to control the directional beam spread, which can be flood (wide) or spot (narrow). It’s a common lamp across commercial, retail, and residential sectors. They have superior photometric qualities in comparison to a BR-series lamp, including reduced glare, and come in a wide range of lumen output.

Each lamp type has a specific base type as well. The light fixture determines whether your lamp is the correct fit.  Some common base types include the following:

Figure 3: Common lamp bases. Source: Leapfrog Lighting

 

GU5.3

A 2-pin base type also known (quite unsurprisingly) as the bi-pin. The figure “5.3” denotes the pin spread or measurements of the pins center to center (it’s actually 5.33mm).

GU10

Also a 2-pin base type, but larger near the ends in comparison to the GU5.3. It’s known as a “twist lock” base type, as a push-then-twist action is required to install the lamp into the fixture. The figure “10” denotes the pin spread (which is this case is actually 10mm).

E26/27

A screw-in base type also known as the Edison screw fitting, as it’s the same threaded metal base used for the A lamp. In North America, the base is E26, and is for a 110-120V AC. In Europe, the base is E27, and is for 220-240V AC.

All UL-certified lamps include a stamp that lists the lamp type, base type, and wattage, so when replacing your lamps with energy-efficient LEDs, it should be fairly straightforward. However, finding a direct replacement for light output is not as straightforward. LED lamps indicate the brightness of the lamp (light output) in terms of lumens, not in Watts like incandescent and halogens. While this might seem confusing at first, it’s actually a more accurate representation, as Watts refers to the amount of power used, not the amount of light emitted.

Can you see why a light bulb isn’t just a light bulb?