Best retro purpose
Metal Hallide lamps are still widely used on commercial, industrial and architectural lighting but in these applications LED lamps are quickly replacing them due to much better performance, lower energy consumption and easy servicing. Light appearance is coll white or daylight, depending on lamp model, with good colour reproduction and low ultraviolet emission. The lamp can be used indoors as well as outdoors, when intense lighting is required as most surrounding look quite pleasing being light with new lamps. With the most common gear, an electromagnetic ballast along with an ignitor, flicker is noticeable.
These type of double-ended lamps were used sometimes for lighting exterior areas, especially for higher powered lamps but the most frequent application was indoor accent lighting with lower wattages. The lamp was relatively affordable (for a metal hallide lamp) and compact, having a successful niche until LED lamps appeared. Since they are very compact light sources it should be noted that heat output is very high, making the lamp unsuitable for open-air operation, seriously limiting flexibility. Another very important limitation is caused by the mandatory operating position and relatively short lamp life. While lamp warm up time is low, with the lamp achieving high output quite quickly, they are slow to restart, 10 minutes pauses not being uncommon. Both high pressure mercury vapour as well as sodium vapour ballasts can be used if provided with a suitable ignitor.
Overall, HQI-E lamps are a mixed success. Some lamps have very good performance, in colour reproduction and service life, others are below average. Most of the product range has widely different specifications which means that a specific lamp has to researched in advance for desirable features. HQI-E lamps that have the internal shroud and are designed for open luminaries should generally be avoided as they have much reduced performance that is significantly below even to standard high pressure mercury vapour lamps, as they have only 6000 hours lifetime and they age quite quickly.
Understanding manufacturer data
Lamp light output is always measured in lumens. This is a way of measuring by averaging light output at a distance of 1 meter in an integrating sphere. This was carried out in lab environments and this information was mentioned in lamp datasheets and catalogues. While this information is accurate it should be considered only across similar lamp types.
Lamp life is presented in thousands of hours. It does not point at a specific moment when an installed lamp will not operate anymore but a statistical point at which some of the lamps may not operate, giving a rough estimate of useful life.
Ra8 colour rendering index, or simply colour rendering index is a way of expressing the typical colour rendering capability of a lamp. While it may be non-intuitive this is a computed average of brightness of certain coloured samples that are light by the lamp. The brighter they are, the more efficient is the lamp in this task. Most lamps do not have a continuous colour spectra so only some specific colours might look very bright and others look very dull. Colour samples are not intense reds, greens and blues but intermediately vivid colours that are focused on human skin colours and some fabrics or surfaces, meaning that a only very high colour rendering indexes are desirable for indoor home lighting. Sun light renders colours almost perfectly, having a value of 100 while typical lamps have a rendering index between 50 and 80, a good value being above 80 and a poor one below 50.
Colour temperature is another important detail. The value is presented in Kelvins and follows a theory that boils down to the fact that light can be produced by heating a metal up to a specific temperature. A camp fire releases light as the flame reaches around 1500-2000 degrees Celsius and a slightly higher value expressed in Kelvin. The designation is warm white for a value of around 2700 Kelvin, natural white with a value of around 3200-3500 Kelvin, cool white for a value of around 4000-4500 Kelvin, daylight for a value between 5000 and 5500 Kelvin, and cool daylight for a value above 6000-6500 Kelvin. There are cultural preferences that make some warm colour temperatures preferred in colder climates and cool colour temperatures in warmer climates. The most popular home lighting worldwide is mostly warm white, due to a comfortable, pleasant atmosphere that is close to the old incandescent lamp.
|Designation||Base||Lamp wattage||Luminous flux||Colour appearance||Colour Temperature||Colour Rendering Index (Ra8)||Life (to 50% failures)|
|HQI-E 70W/WDL clear/ sleeve (730)||E27||70 W||5200 lm||Warm White||3000 K||70||9000 hours|
|HQI-E 70W/WDL coated/ sleeve (729)||E27||70 W||4700 lm||Warm White||2900 K||70||9000 hours|
|HQI-E 70W/NDL clear/ sleeve (742)||E27||70 W||5500 lm||Cool White||4200 K||70||6000 hours|
|HQI-E 70W/NDL coated/ sleeve (740)||E27||70 W||5100 lm||Cool White||4000 K||70||6000 hours|
|HQI-E 100W/WDL clear/ sleeve (830)||E27||100 W||8500 lm||Warm White||3000 K||85||9000 hours|
|HQI-E 100W/WDL coated/ sleeve (829)||E27||100 W||7900 lm||Warm White||2900 K||80||9000 hours|
|HQI-E 100W/NDL clear/ sleeve (742)||E27||100 W||8400 lm||Cool White||4200 K||70||6000 hours|
|HQI-E 100W/NDL coated/ sleeve (740)||E27||100 W||7700 lm||Cool White||4000 K||70||6000 hours|
|HQI-E 150W/WDL clear/ sleeve (730)||E27||150 W||12900 lm||Warm White||3000 K||70||9000 hours|
|HQI-E 150W/WDL coated/ sleeve (729)||E27||150 W||11600 lm||Warm White||2900 K||70||9000 hours|
|HQI-E 150W/NDL clear/ sleeve (842)||E27||150 W||12500 lm||Cool White||4200 K||80||6000 hours|
|HQI-E 150W/NDL coated/ sleeve (840)||E27||150 W||11500 lm||Cool White||4000 K||86||6000 hours|
|HQI-E 250W/D coated/ sleeve (952)||E40||250 W||17000 lm||Daylight||5200 K||90||6000 hours|
|HQI-E 250W/D coated (952)||E40||250 W||19000 lm||Daylight||5200 K||90||12000 hours|
|HQI-E 400W/D coated (953) NAV-VG||E40||400 W||34000 lm||Daylight||5300 K||90||12000 hours|
|HQI-E 400W/D coated (955) HQI-VG||E40||400 W||26000 lm||Daylight||5500 K||90||12000 hours|
|HQI-E 400W/D coated/ sleeve (947) NAV-VG||E40||400 W||31000 lm||Daylight||4700 K||90||12000 hours|
|HQI-E 400W/D coated/ sleeve (952) HQI-VG||E40||400 W||25000 lm||Daylight||5200 K||90||12000 hours|
|HQI-E 400W/N clear (640) NAV-VG *||E40||400 W||34000 lm||Cool White||4000 K||65||12000 hours|
|HQI-E 400W/N clear (646) HQI-VG *||E40||400 W||26000 lm||Cool White||4600 K||60||12000 hours|
|HQI-E 400W/N coated (638) NAV-VG *||E40||400 W||40000 lm||Cool White||3800 K||65||12000 hours|
|HQI-E 400W/N coated (640) HQI-VG *||E40||400 W||34000 lm||Cool White||4000 K||60||12000 hours|
|HQI-E 1000W/N coated (638) *||E40||1000 W||100000 lm||Cool White||3800 K||65||9000 hours|
- "sleeve" indicates an internal sleeve placed that protects against arc tube shattering risk in open luminaires;
- NAV-VG indicates that the 400W lamp is designed for high pressure sodium vapour lamp gear;
- HQI-VG indicates that the 400W lamp is designed for metal hallide lamp gear; lower lumen output due to lower lamp current;
- "*" indicates lamps that are suited for horizontal rather than universal operating position
Durability and Repair-ability
Generally, metal hallide lamps fare quite poorly in terms of reliability but some lamps have an outright poor performance. The aggressiveness of metal hallides and their reliance on a specific pressure and temperature requirement for vaporization and light output with a specific output, means that lamp to lamp colour shifts are quite noticeable. Aging amplifies the colour drift and light output differences. As the lamp is very compact and has high temperature hot-spots means that fixtures are noticeably degraded and especially affects gaskets and the front frame of the reflector housing. This means that waterproofing is frequently degraded and lamps are rarely suited to operate outdoors unless old fixtures are carefully maintained.
The lamps themselves are quite short living, some having only a 6000 hour lifetime while others have double this value. This wide discrepancy makes some lamps useless as they are already quite rare and they may be still expensive to purchase as new. Electronic gears were available but quite rarely used due to their much higher price, although lamps service lamp may be increased and the hot restart or restrike of lapms in case of power outages or starts and stops seriously improves versatility. On the other side, electronic gears are affected much quicker than conventional gears so their useful life may be already halved due to aging components, mandating some future repairs or replacements. Due to large starting voltages special care should be taken for proper insulation and wiring of the lamp and gear.
Greatest features & flaws
|High light output in very compact package||Hot operating fixtures, maintenance intensive|
|High efficiency, sometimes good colour rendering||Some lamps have very short service life|
|Directional light||Sensitive to operating position and unbalanced wearing on some lamps|
|Quick lamp start||Widely different lamps, slow restart, bulky, complex lamp gear|
These metal hallide lamps are suited for both indoor and outdoor aplications but there are some precautions that should be taken. The lamp range is highly diverse. Colour reproduction varies widely between different power ratings and some lamps are available with only a single white light appearance or colour temperature. This means that all attempts at finding an application have to be based on prior analysis of the datasheet as even slight differences in specifications have an impact on applications. While the lamp portfolio covers wattages from 70 to 1000W, there are certain ranges that seem to be highly popular such as 70W as well as the 400W. The lamps themselves fares well in terms of light output but the point light source nature of the lamp relegates it to accent or directional rather than general lighting.
The lamp's performance is mixed. There are some lamps that have colour rendering indexes of 90 but there are others that have only 60 and, generally, better colour reproduction comes with shorter service lives and this is especially unfortunate for lamps that are suited for operation in open fixtures. Also, some lamps should be avoided, as is the case for the ones suited for operation on conventional metal hallide (actually designed for mercury vapour, with an added parallel ignitor). Of course, compared with ceramic metal hallide lamps, HQI lamps are sometimes performing below average or above average quartz lamps, but performance inconsistencies, such as horizontal operating position for certain lamps, seem to be compound limitations.
These lamps are somewhat better suited for frequent switching but starting is still a major stress. They need less than two minutes to reach maximum light output and less than that to restart after being turned off. The light colour and output changes from start-up to normal operation from white to orange. White light at startup and then greenish light midway to warm-up suggests mercury is also used on the lamp. This slightly improves colour rendering but affects slightly reduces lamp life while the ones that do no change colour are either new or do not use mercury at all have a yellower light appearance. Lamps without mercury are more difficult to start but they have longer lifetimes and slightly higher efficiency.
The lamp requires a conventional or electro-magnetic gear of the same power output as the lamp, connected in series with a lamp and an ignitor that must be connected as is required in the circuit. Connecting the lamp directly to mains damages it instantly as there is no current limitation. Improper connection of the ignitor is also dangerous and proper care must be exerted during installation and servicing. A power factor capacitor that has a specific value might be used to correct the power factor and current requirements on the circuit. The lamp itself is not influenced by the presence or absence of this capacitor. When used sparingly in homes or some premises where not a lot of these lamps are located, power factor correction is not important but large industrial or commercial clients were required to maintain a specific power factor due to electricity distribution contracting. Also, special care should be exercised as some 400W and 1000W lamps should be operated only horizontally.
There are lamps that are designed for operation in closed and enclosed fixtures. An added advantage of eliptical lamps compared with tubular lamps, and especially for the Osram HQI range, is that lamps can be used in universal position, opening many interior and exterior operation possibilities. Indoor lighting is mostly limited by requirements of hard to find electronic gear that eliminates flicker and improves lifetime as well as provide quick lamp restart. Conventional gear is available but hum, flicker, wiring complexity are unavoidable.
Coated lamps should be used where lamps are used in open fixtures due to less glare, while uncoated lamps are much more efficient in enclosed fixtures that almost always have reflectors or internal surfaces that help direct light. Operating position limitations for 400W and 1000W lamp types are a nuisance when attempting to achieve certain colour and light output specificity.
Lower rated power output gears can be used, but it is not recommended as colour reproduction and lamp lifetime will be reduced while higher powered ones damage the lamp due to over-stressing and is highly dangerous. Used lamp gears might work but old lamps are never desirable as they degrade much quicker than mercury vapour and sodium lamps. Rusted ballast may still operate but are a potential hazard while old, used lamps, may not have much useful life left and they may already exhibit some colour light emission issues. New old-stock lamps are the best choice, if available.
The lamp technology was an improvement of previously developed mercury vapour lamps. The potential for fluorescent powders was mostly exhausted by early 70s which meant that research concentrated on releasing better lamps that produced light directly from the discharge tube. This research was also carried previously but results were modest, as stable compounds with good colour reproduction were found to be quite aggressive and lead to short service life. Sodium, Scandium, Indium, Thallium were attempted as main elements that can offer a balanced light output but they required a specific balance of temperature and pressure to achieve best results. One major limitation was that certain compounds were costly or difficult to manufacture or mix in specific amounts, which meant that suitable results could not be found for many decades. In the late 70s and early 80s most major manufactures were able to center on specific technologies that reached good enough results for general lighting, with predictable performance.
The HQI-E range was the result of research aimed at creating lower powered metal hallide lamps that had better colour reproduction and energy efficiency compared with high pressure mercury vapour lamps. The most important limiting factor was that the arc tube had to be formed more evenly at the ends and be reasonably well insulated and heat resistant to ensure reasonable performance. More advanced manufacturing tools and processes had to be developed. The arc tube was well built to resist the long term corrosive nature of hallides. It was also important to ensure less variations in arc tube geometry as well as temperature profile. This meant that heat reflecting coatings were mandatory for the arc tube. As soon as all these conditions were met, the lamp was released. Osram had superior manufacturing technology that allowed better performing lamps but the range itself was confusing, as inconsistencies between different lamp types are hard to undestand.
Products were quite successful on the market until the advent of the much improved ceramic tube metal hallide lamps, around mid 1990s. Although ceramic hallide lamps were much more expensive, their better colour reproduction, lamp life and efficiency meant that there were few reason to choose HQI-E lamps. However, the higher wattage and white appearance choices made this lamp range more appreciated on the market than the Philips HPI lamps, especially on markets where variety was valued. Although less affected than Philips due to market stability in many countries, Osram HQI-E lamp installations were experiencing a slow demise. While LED light sources were taking over the market in late 2000s, Osram did not heavily promote LED lamps as much as Philips did.
Most manufacturers have been releasing lamps for many decades and constantly improved technology so that lamps had a stabler, predictable lifetime and slightly improved colour stability due to manufacturing progress.
Compared with Philips HPI lamps, the HQI-E range is much more diverse, offering a wider selection of wattages as well as more white colour choices. However, service lifetime and white light appearance varies much more than on Philips lamps, being less predictable based on some widely used assumptions in general lighting.