Multifaceted reflector

Left to right: MR16 with GU10 base and with GX5.3 base, MR11 with GU4 or GZ4 base

MR16 and MR11 (sometimes referred to as MR-16 or MR-11, rarely MR8 or MR-8) are standard formats for halogen multifaceted reflector light bulbs made by a variety of manufacturers. MR16-compatible LED lamps are also available. MR16 lamps are regularly used in place of standard incandescent light bulbs for applications including residential lighting and retail lighting, while MR11 ones are used in specialty applications. MR16 lamps were originally designed for use in slide projectors. They are well suited to a variety of applications that require directional lighting of low to medium intensity, such as track lighting, recessed ceiling lights (only if not dichroic^[1][2]), desk lamps, pendant fixtures, landscape lighting, retail display lighting and bicycle headlights.^{[citation needed]}

Designation

MR16 is a coded designation in which MR stands for multifaceted reflector, and 16 is the number of eighths of an inch the front is in diameter. An MR16 is 2 inches (51 mm), an MR11 is 1.375 inches (35 mm).

Halogen MR16 characteristics

Design and construction

Halogen MR16 lamps consist of a halogen capsule (bulb) integrated with a pressed glass reflector. The reflector of an MR16 lamp is 2 inches (51 mm) in diameter. The base conforms to bi-pin GU5.3 standard. The compact size of the MR16 allows for much smaller, more discreet fixtures than the incandescent reflector bulbs that pre-dated MR16s.

The reflector controls the direction and spread of light cast from the lamp. MR16 lamps are available with different beam angles from narrow spot lights of as small as 7° to wide flood lamps of 60°.

"MR" refers to multifaceted reflector, indicating that this reflector is usually shaped with multiple small facets. This multifaceted reflector gives a soft edge to the area illuminated by the lamp. MR16 lamps are also available with smooth reflectors, resulting in a sharper fall-off to the illuminated area. "16" refers to the maximum diameter of the lamp in eighths of an inch, 16/8" or 2 inches (51 mm).

Dichroic reflectors

Some lamps use aluminum coating as a reflector while some lamps use selective pass/block dichroic coating that reflects particular frequencies of the visible spectrum in the direction the lamp is facing, while not reflecting infrared light. By not reflecting infrared light (which produces heat), these lamps reduce the amount of heating of the subject upon which they are focused.

IEC 60598 No Cool Beam symbol

Dichroic lamps, however, must never be used in recessed lighting, as they are a common ignition source for building fires.^[1][2] In some countries, e.g., the EU and Australia, lamps unsuitable for use in recessed lighting can be identified by the IEC 60598 No Cool Beam symbol.

Operation

The brightness of MR16 lamps can be adjusted when used with appropriate light fixtures and dimmers. However, the color temperature changes significantly when the lamp is dimmed.

MR16 lamps produce significant heat, and care must be taken to avoid contact with skin or proximity to flammable materials when the lamp is on or has been on recently.

Low voltage halogen lamps, such as MR16 lamps often has a better efficacy than line voltage incandescent lamps but not nearly as efficient as gas discharge lamps or some LED lamps.

With both types of incandescent bulbs, useful life can be considerably shortened if their filaments experience mechanical shock or vibration. Using an electronic transformer with a "soft start" feature can considerably extend life, as it reduces the characteristically high inrush current that occurs initially when the lamp is cold.

MR16 lamps, like all quartz-halogen lamps, produce some ultraviolet light. Usually, this must be filtered out. Also, the quartz capsule of the lamp sometimes ruptures ("explodes") upon failure of the lamp. For these two reasons, some MR16 lamps include a cover glass that serves as an integrated ultraviolet filter and explosion shield. MR16 lamps lacking this cover require the use of a fixture that incorporates an external piece of glass specifically designed to provide this protection.

MR16 lamps are available in 10–50 W power ratings (150–800 lumens).^[3]

Compatible LED replacements

Main article: LED bulb

LED MR11, 70 lm/W LED MR16

MR16-compatible LED lamps are also available. They are similar in shape to halogen MR16 lamps, and can be used in most fixtures designed for MR16 lamps. The same is true of MR11-compatible LED lamps.

Versions of the led lamps have been patented in the UK.{PATENT NO.GB2397943} Due to the low heat and power consumption, they have been produced from plastic, although this does not affect their efficiency. Their non-polarised AC/DC operation, with current limitation over a wide voltage range (11.5 ~ 18 volts as a standard 12 volt version), allows a wide range of usage.

Average rated life, as quoted by manufacturers, is typically 30,000 to 50,000 hours, depending on the product. This amounts to continuous operation for 1250 to 2080 days, or approximately 24 hours per day for three to six years.

Fixtures designed for halogen MR16 or MR11 lamps that use electronic transformers may need to be retrofitted with LED-compatible transformers. This is because the standard electronic transformers have a minimum power-usage requirement in order to function. Some LED-lamps may be below this usage requirement. Fixtures that use magnetic transformers can generally be used with LED-lamps without modification.

LED-lamps from some manufacturers incorporate full wave rectification circuitry into the lamp, so that either AC or DC can be used, while others require a DC supply and correct polarity.

At this time,^[when?] there are few standards for MR16 and MR11 compatible LED lamps. As such, there is a wide variety of designs, varying significantly with regard to beam width, light colour, efficiency and luminous power.

Unlike halogen MR16s, LED-lamps often do not have the multifaceted reflectors that give MR16s their precise beam width control. Some rely on the optics of the LED(s) to control the beam width. Some designs may have simple cut-off apertures that limit beam width, or even individual reflectors for each LED.

As with other LED lamps available today, the quality and color temperature of the white light produced by such lamps varies. Many tend towards the blue end of the spectrum, being even "cooler"-coloured than fluorescent lighting. Because of this variability, some MR16 and MR11 compatible LED lamps will create significantly more natural looking light than others.

The least efficient of these lamps produce about 26 lumens per watt (lm/W), which is similar to the efficiency of halogen MR16s. The most efficient of these lamps available today produce about 100 lm/W, which exceeds the efficiency of compact fluorescent lamps.

In terms of total luminous power, such lamps range from being significantly less powerful than their halogen counterparts, to being comparable to the lower power halogen MR16s. The brightest available halogen MR16s are still slightly brighter than the brightest available LED versions.

Variations

MR16 lamps most often operate at 12 volts, although they are also available in other voltages. The common 12-volt MR16 lamps, therefore, require a ferromagnetic or electronic transformer — sometimes misnamed as a ballast — to convert the 120 or 230 volt mains voltage to the very low operating voltage required by the lamp. MR16 lamps may also be operated from direct current, but will have a shortened life.

Although halogen incandescent MR16 lamps usually operate on AC voltage, LED devices require direct current and require a rectifier and current driver in the unit. The current driver is commonly a buck–boost converter or buck converter. The rectifier must be able to operate efficiently at the high frequencies produced by electronic transformers and should also incorporate safety devices that operate in the event of component failure.^[4]

Certain MR16 lamps can operate directly on the mains voltage. These lamps typically use a GU10 turn-and-lock base, so they cannot be accidentally interchanged with low-voltage lamps. They are often referred to as GU10, rather than MR16 lamps. Because their filaments are finer, they are much more fragile than those used in low-voltage lamps.

Low-voltage MR16 lamps almost always have ANSI standard GU5.3 two-pin bases. MR16 lamps with an integrated transformer are also available. These lamps have screw bases to fit standard medium-base Edison sockets.

Smaller lamps are also manufactured in the less common MR11 and even less common MR8 formats, which have reflectors that are 1⅜ inch (11/8" or 35 mm) and 1 inch (8/8" or 25 mm) in diameter, respectively. These smaller lamps appear very similar to MR16 lamps, also featuring similar multifaceted reflectors that are available in a variety of beam spreads. Their smaller size makes possible even smaller fixtures, but limits them to lower powers. MR11 and MR8 lamps have pins placed closer together, preventing them from accidentally being interchanged with MR16 lamps.

PQL INC. Produces a wide variety of color temps. in 3W LED MR16's 30K,35K,50K and 65k for precise color applications and specialty installations including landscape lighting. These lamps replace a 35W MR16.

Advantages

MR16 lamps offer several advantages over other lamps with equivalent wattage ratings. They are typically smaller (transformers excepted), provide better beam control and offer a whiter light than ordinary incandescent lamps. The small size of the lamp allows designers more flexibility in placing the lamps and with the option of various beam widths, the light beam can be very specifically placed. The light output properties of the LED lamps provides a whiter light (higher color temp and higher Color Rendering Index) that enhances the color of illuminated objects.

Disadvantages

MR16 lamps have several disadvantages over other types of lighting, most notably their high operating temperature and pressurized bulb. The halogen bulb can reach temperatures over 200°C, increasing the risk of fire should anything flammable come in contact or even be in close proximity to the bulb or fixture. The quartz capsule containing the filament and halogen gas is pressurized and can explode if improperly handled or damaged, and must be handled carefully prior to installation to prevent contamination with oil and salt from fingerprints, which can dramatically shorten the lamp's life.

Mounted clear of roof insulation and with an inbuilt air space around the luminaire fitting, they effectively form small chimneys resulting in heat lost from the room space to the roof space.

In dusty environments, the high temperatures produced contribute to a burnt smell; depending on the type of dust, the smell can be as pleasant as toast or as bad as having a nearby oil refinery.

Compact fluorescent versions that can replace the MR16 exist, run at safe temperatures, and consume only a few watts, but typically scatter the small amount of light produced widely, thus making them suitable only for limited applications.

ANSI designations

A typical MR16 lamp

The following ANSI standard codes are used to designate certain power and beam angle combinations for MR16 lamps. Many manufacturers use these standard codes for lamps matching these specifications:

• ESX: 20 watt, 10 degree beam (20MR16/10°)
• BAB: 20 watt, 35 degree beam (20MR16/35°)
• EXT: 50 watt, 15 degree beam (50MR16/15°)
• EXZ: 50 watt, 25 degree beam (50MR16/25°)
• EXN: 50 watt, 40 degree beam (50MR16/40°)
• FNV: 50 watt, 60 degree beam (50MR16/60°)
• FPA: 65 watt, 15 degree beam (65MR16/15°)
• FPC: 65 watt, 25 degree beam (65MR16/25°)
• FPB: 65 watt, 40 degree beam (65MR16/40°)
• EYF: 75 watt, 15 degree beam (75MR16/15°)
• EYJ: 75 watt, 25 degree beam (75MR16/25°)
• EYC: 75 watt, 40 degree beam (75MR16/40°)

Note that MR16 lamps are available in many other power and beam combinations than those available above. For this reason, MR16 lamps are also often labeled according to beam spread abbreviations. Note that these while these abbreviations are commonly used, the angles associated with these abbreviations vary slightly from manufacturer to manufacturer. These are typical beam angles for these beam spread abbreviations

• VNSP (very narrow spot): less than 8 degrees
• NSP (narrow spot): 8-15 degrees
• SP (spot): 8-20 degrees
• NFL (narrow flood): 24-30 degrees
• FL (flood): 35-40 degrees
• WFL (wide flood): 55-60 degrees
• VWFL (very wide flood): 60 degrees or more

See also

• Luminous flux
• Bipin
• Edison screw
• Bayonet mount

References

1. ^ ^{a b} [1], Cheshire Fire and Rescue Service: Incidents.
2. ^ ^{a b} [2], Electrical Safety Council: Downlighters can they be a fire hazard?
3. ^ "Replace Inefficient MR16 Halogen Lamps with LEDs". Maxim. September 25, 2007. http://www.maxim-ic.com/app-notes/index.mvp/id/4086. 
4. ^ [3], MAXIM: LED driver solution for MR16 and similar retrofit lamps

External links

• MR16 Q&A from Lighting Research Center