I am now aware of many combinations of mismatched ballasts and lamps that will run just fine. I know that most MV lamps have a matching MH ballast of a lower wattage, but I am wondering what YOU know. What strange combinations of United States ballasts and lamps are you aware of that will work just fine (or just "good enough")?

Don't correct other people's comments if you think they are wrong, this is a widely disputed topic that has many caveats, nothing is absolute but try and provide evidence for your claims if you have any.

Thanks!

Edit: Not super interested in fluorescent, mainly HID. Sorry forgot to put that in the post.

Most electronic T12 ballasts will run T8s. I see this all the time, as people are used to buying the "normal" T12 tubes instead of the "thin" T8s.

An F20T12 ballast will run a F17T8 lamp well enough, but it tends to flicker a bit.

I use MV and MH lamps interchangeably on my probe start metal halide 400W fixture.

Electronic F20T12 ballast should run European 18W T8 without problems, if its OCV is sufficiently high.

Most older HID lamps (pre-2000) work remarkably well on a ballast type that may be very different than specified.  Both the lamps as well as older magnetic ballasts were over-engineered and can deliver very good performance over a wide range of powers.  In that respect they are considerably more robust than incandescent, halogen and fluorescent lamps whose performance varies drastically with only small power fluctuations.

Mercury and sodium lamps still deliver excellent performance when quite significantly over-run, with only very limited life reduction.  Conversely, under running does not usually reduce life very much and can reduce power consumption along with light output - although with a rather greater drop in efficacy.   Since the customer must also buy the electricity required to run the lamp, and that typically costs far more than the lamp itself, the biggest drawback of not using the correct ballast is often a drop in efficacy and rise in operating costs.  If lower light output is desired, it is always more efficient to use a lower power lamp with its matching ballast.  Conversely for higher light output, using the correct match will reduce the nuisance and cost of too frequent maintenance cycles.

The USA however became somewhat obsessed with matching lamps and ballasts exactly - to the extent that it established a unique system of lamp and ballast codes that are unknown elsewhere.  It even went so far as to intentionally hide lamp and ballast electrical parameters so that customers could not make their own educated assessments of how to run their lamps.  As a result, lamp:ballast mismatches are rare but in other global regions much more common.  For instance in Europe metal halide lamps designed for sodium ballasts are very often run on mercury gear and vice-versa.  Although non-optimal, I am certain that most customers are never aware of the slight loss of performance.  Over the years this even inspired manufacturers to make dual-rated lamps that operate with excellent performance on ballasts that might drive the lamps on ballasts rated for up to 40% different currents.  For brief periods, operation at doubled or halved power is easily possible.

The situation is however very different for modern metal halide lamps, especially the more recently developed ceramic types.  Those were typically optimised for very high efficacy and/or colour rendering quality, and push their raw materials to the absolute limits in terms of thermal loading, corrosion resistance, and chemical rejuvenation cycles that ensure excellent lumen maintenance.  Some of these effects are also true for white-light HPS lamps.  Small power changes can tip any one or more of these features over the limits, with disastrous consequences on efficacy, colour quality or life.  They may well even explode or fail catatrophically. The power requirements are often so precise that only electronic ballasts are possible, to avoid the small power differences that can be caused by mains voltage fluctuations.

It’s also worth remembering that unmatched combinations can damage the ballasts as well as the lamps.  A low voltage sodium or metal halide lamp on a mercury ballast designed for a higher voltage lamp can cause overheating and reduced life/efficacy.  Similarly, lamps having internal starters that produce a higher voltage pulse may break down the insulation on older ballasts.

Conclusion, for anything other than cost-optimised commercial lighting applications, do not be afraid to run HID lamps on ballasts that may be very different than intended.  For collectors and lighting enthusiasts it would be rare to create any really undesirable situations.  But always wear a pair of safety glasses if you intend to severely overrun any lamp!

@James oooh, I was wondering about those lamp codes (s66 for example). That's really cleared it up!

Most older HID lamps (pre-2000) work remarkably well on a ballast type that may be very different than specified.  Both the lamps as well as older magnetic ballasts were over-engineered and can deliver very good performance over a wide range of powers.  In that respect they are considerably more robust than incandescent, halogen and fluorescent lamps whose performance varies drastically with only small power fluctuations.

Mercury and sodium lamps still deliver excellent performance when quite significantly over-run, with only very limited life reduction.  Conversely, under running does not usually reduce life very much and can reduce power consumption along with light output - although with a rather greater drop in efficacy.   Since the customer must also buy the electricity required to run the lamp, and that typically costs far more than the lamp itself, the biggest drawback of not using the correct ballast is often a drop in efficacy and rise in operating costs.  If lower light output is desired, it is always more efficient to use a lower power lamp with its matching ballast.  Conversely for higher light output, using the correct match will reduce the nuisance and cost of too frequent maintenance cycles.

The USA however became somewhat obsessed with matching lamps and ballasts exactly - to the extent that it established a unique system of lamp and ballast codes that are unknown elsewhere.  It even went so far as to intentionally hide lamp and ballast electrical parameters so that customers could not make their own educated assessments of how to run their lamps.  As a result, lamp:ballast mismatches are rare but in other global regions much more common.  For instance in Europe metal halide lamps designed for sodium ballasts are very often run on mercury gear and vice-versa.  Although non-optimal, I am certain that most customers are never aware of the slight loss of performance.  Over the years this even inspired manufacturers to make dual-rated lamps that operate with excellent performance on ballasts that might drive the lamps on ballasts rated for up to 40% different currents.  For brief periods, operation at doubled or halved power is easily possible.

The situation is however very different for modern metal halide lamps, especially the more recently developed ceramic types.  Those were typically optimised for very high efficacy and/or colour rendering quality, and push their raw materials to the absolute limits in terms of thermal loading, corrosion resistance, and chemical rejuvenation cycles that ensure excellent lumen maintenance.  Some of these effects are also true for white-light HPS lamps.  Small power changes can tip any one or more of these features over the limits, with disastrous consequences on efficacy, colour quality or life.  They may well even explode or fail catatrophically. The power requirements are often so precise that only electronic ballasts are possible, to avoid the small power differences that can be caused by mains voltage fluctuations.

It’s also worth remembering that unmatched combinations can damage the ballasts as well as the lamps.  A low voltage sodium or metal halide lamp on a mercury ballast designed for a higher voltage lamp can cause overheating and reduced life/efficacy.  Similarly, lamps having internal starters that produce a higher voltage pulse may break down the insulation on older ballasts.

Conclusion, for anything other than cost-optimised commercial lighting applications, do not be afraid to run HID lamps on ballasts that may be very different than intended.  For collectors and lighting enthusiasts it would be rare to create any really undesirable situations.  But always wear a pair of safety glasses if you intend to severely overrun any lamp!

It was very common here to run probe-start MH lamps like Osram HQI-T 400W/N/SI on a HPS gear with HV ignitor or a MV gear with HV igntior instead of MV gear and LV parallel ignitor or an autoregulator ballasts. Also: I've seen Osram HQI-BT 400W/D and Chinese clones operating on Chinese MV ballasts that glowing greenish white instead of 6000K white light.

Most older HID lamps (pre-2000) work remarkably well on a ballast type that may be very different than specified.  Both the lamps as well as older magnetic ballasts were over-engineered and can deliver very good performance over a wide range of powers.  In that respect they are considerably more robust than incandescent, halogen and fluorescent lamps whose performance varies drastically with only small power fluctuations.

Mercury and sodium lamps still deliver excellent performance when quite significantly over-run, with only very limited life reduction.  Conversely, under running does not usually reduce life very much and can reduce power consumption along with light output - although with a rather greater drop in efficacy.   Since the customer must also buy the electricity required to run the lamp, and that typically costs far more than the lamp itself, the biggest drawback of not using the correct ballast is often a drop in efficacy and rise in operating costs.  If lower light output is desired, it is always more efficient to use a lower power lamp with its matching ballast.  Conversely for higher light output, using the correct match will reduce the nuisance and cost of too frequent maintenance cycles.

The USA however became somewhat obsessed with matching lamps and ballasts exactly - to the extent that it established a unique system of lamp and ballast codes that are unknown elsewhere.  It even went so far as to intentionally hide lamp and ballast electrical parameters so that customers could not make their own educated assessments of how to run their lamps.  As a result, lamp:ballast mismatches are rare but in other global regions much more common.  For instance in Europe metal halide lamps designed for sodium ballasts are very often run on mercury gear and vice-versa.  Although non-optimal, I am certain that most customers are never aware of the slight loss of performance.  Over the years this even inspired manufacturers to make dual-rated lamps that operate with excellent performance on ballasts that might drive the lamps on ballasts rated for up to 40% different currents.  For brief periods, operation at doubled or halved power is easily possible.

The situation is however very different for modern metal halide lamps, especially the more recently developed ceramic types.  Those were typically optimised for very high efficacy and/or colour rendering quality, and push their raw materials to the absolute limits in terms of thermal loading, corrosion resistance, and chemical rejuvenation cycles that ensure excellent lumen maintenance.  Some of these effects are also true for white-light HPS lamps.  Small power changes can tip any one or more of these features over the limits, with disastrous consequences on efficacy, colour quality or life.  They may well even explode or fail catatrophically. The power requirements are often so precise that only electronic ballasts are possible, to avoid the small power differences that can be caused by mains voltage fluctuations.

It’s also worth remembering that unmatched combinations can damage the ballasts as well as the lamps.  A low voltage sodium or metal halide lamp on a mercury ballast designed for a higher voltage lamp can cause overheating and reduced life/efficacy.  Similarly, lamps having internal starters that produce a higher voltage pulse may break down the insulation on older ballasts.

Conclusion, for anything other than cost-optimised commercial lighting applications, do not be afraid to run HID lamps on ballasts that may be very different than intended.  For collectors and lighting enthusiasts it would be rare to create any really undesirable situations.  But always wear a pair of safety glasses if you intend to severely overrun any lamp!

Well yeah you can put any lamp in any ballast, but I was more so wondering about the combinations that will work long-term. I know that if you just want to test a lamp you can do whatever you want, but I want them to last a long time.

Interestingly, unlike in Europe and North America, I have seen that Japan in particular has marketed most of its medium and high wattage high pressure sodium lamps and metal halide lamps as direct retrofit lamps for mercury vapor ballasts, which certainly helps reduce the likelihood of mismatching between lamps and ballasts as long as the wattage matches or is close enough such as 400W quartz metal halide retrofit lamps being designed for 400W mercury vapor ballasts or 360W high pressure sodium retrofit lamps designed for 400W mercury vapor ballasts.

Even though the information I explained above is largely true for many Japanese HID lamps, I am also aware of some Japanese high pressure sodium lamps and metal halide lamps being designed for dedicated ballasts. Dedicated ballast high pressure sodium and metal halide lamps tend to be more of a thing for low wattage lamps and sometimes for high wattage quartz metal halide lamps sold there. I have read about dedicated ballast medium wattage high pressure sodium and metal halide lamps being sold in Japan, but they tend to be less common.

Another thing to keep in mind when ensuring that HID lamps last for as long as possible is that if you are using HX and reactor ballasts, you generally want to ensure that the ballast is running as close to its correct line voltage and frequency as much as possible since a higher line voltage could easily overdrive the lamp and a lower line voltage could easily underdrive the lamp.

If you do have concerns about severe line voltage fluctuations, a CWA ballast or CWI ballast would be more optimal as they tend to run lamps relatively close to the correct current even if the line voltage fluctuations are significant.