Hi,

I'm new here. I always had an interest in mercury vapor lamps since I was a kid, but never really got deeply into lighting.

I've got two outdoor lights on the side of my workshop building that are incandescent. Instead of putting an LED to upgrade them, I decided I want to put mercury vapor instead. I thought I should go with 100W cause that comes in a medium base that should fit the existing socket. The ballast will be indoors on the wall feeding out a tube to the light. Are there any high voltages created that would make this standard light fixture not work?

I'd prefer to use an enclosed ballast for safety, but I can't find any mercury vapor ballast that isn't some old honker. My question is: can I use this F-can metal halide ballast: https://ballastshop.com/11210-239c-tc-universal-metal-halide-fcan-ballast-100w-m90/
It says only M90, but annoyingly the 175W model says H39, so maybe it would work anyway?

If not, can I get some traditional mercury vapor ballast that is installed in an enclosure? I almost found one, but the site is broken. I could do it myself I guess, but this is not my primary project and I've got other stuff I want to focus on.

One side question: Can I run for example, two 50W mercury with a 100W ballast?

Appreciate any help. Thanks

Maybe this guy would sell a couple ballast boxes separately?  https://www.ebay.com/itm/Box-of-Greenlee-Lighting-Transformer-Ballasts-and-other-components/202164608590

1.For lower wattage ballasts I believe you need to disconnect the high voltage igniter and use the next size smaller ballast, i.e. a 100w lamp on a 70w ballast.

2.No, I think a 50w mv lamp runs at ~100v 0.6a and a 100w one is 130v 0.8a?  Operating discharge lamps in parallel doesn't work because whichever one strikes first hogs all the current.

OK. I think I might go with a 50W and a T12 ballast instead of trying to find a merc vape one.

Do you think this would work: https://www.ebay.com/itm/SYLVANIA-QT2X40-120-DL-FLUORESCENT-BALLAST-2-LAMP-FT40DL-40W-DL40-120V/333814211397

Or would I need an actual T12 ballast such as this: https://www.ebay.com/itm/Sylvania-MB2x40-120-RS-120V-Magnetic-Ballast-for-two-4-ft-F34-F40-T12-FLUR-bulbs/253950155415

And with one of these, I'm thinking I might be able to run both lights off it because it's meant for 2 T12s.

Found another: https://ballastshop.com/806-slh-tc-p-magnetek-magnetic-fluorescent-ballast/

This one says F72T12, F84T12, F96T12, F96T12ES
These are a bit higher power bulbs. Maybe it could run a 75W or 100W mercury?

Those Greenlee Lighting boxes would be perfect for your application, if you're looking to run 100w MV. The 70w MH ballasts would also run 100w MV but you need to have access to the ignitor to wire it out of the circuit.

I would personally just buy a loose core and coil style ballast and then install it in a metal pull box from Home Depot or something. 35w magnetic MH will run 50w MV, 50w MH will run 75w MV close to the original specs. Don't use a fluorescent ballast though as most have a different voltage and current profile compared to MV lamps, even if the wattage is the same.

The easier would be to buy the corect ANSI rated ballast but due to energy regulations, all the major manufacturers stopped making MV ballasts after 2008.

If you want to operate a high intensity discharge lamp properly, what you need to do is to run it at its proper arc voltage and current. If a high intensity discharge lamp is drawing too much current from a ballast, the lamp is overdriven and burns more brightly than it should and will not last as long as it should. When a high intensity discharge lamp is being driven with not enough current, the lamp will suffer sputtering from the electrodes and operate dimmer than it should. When a high intensity discharge lamp is operated on a ballast that has too low of an open circuit voltage (OCV), the lamp will cycle, meaning that the lamp’s arc is not receiving enough voltage to remain stabilized. If a high intensity discharge lamp is operated with too high of an arc voltage, the ballast will be overheated. In addition, you are totally welcome to experiment with high intensity discharge lamps with incompatible ballasts if you know what you are doing. If you are just new to high intensity discharge lighting (assuming you live in North America), you should be able to operate high intensity discharge lamps properly by matching the correct ANSI ballast for your lamps. If you are interested in collecting high intensity discharge lamps outside of North America and want to operate them properly and experiment with alternative ballasts for your lamps, the most important thing is to run your lamps at the proper arc voltage and current as long as you are able to start it correctly using an appropriate ignitor if the ignition voltage is too low.

If you want to operate a high intensity discharge lamp properly, what you need to do is to run it at its proper arc voltage and current. If a high intensity discharge lamp is drawing too much current from a ballast, the lamp is overdriven and burns more brightly than it should and will not last as long as it should. When a high intensity discharge lamp is being driven with not enough current, the lamp will suffer sputtering from the electrodes and operate dimmer than it should. When a high intensity discharge lamp is operated on a ballast that has too low of an open circuit voltage (OCV), the lamp will cycle...

OK. Thanks for getting back to me. Yes, I'm in USA. I like experimenting with things and have a fair amount of electronics knowledge, just not in the area of lighting. I found three good potential options:
https://www.ebay.com/itm/SYLVANIA-MB2X96-VHO-120-RS-NEW/333559047792
https://www.ebay.com/itm/SYLVANIA-MAGNETIC-BALLAST-MB2X96-HO-120-RS-120V-60HZ-2-05A/362496187458
https://www.ebay.com/itm/NEW-PHILIPS-ADVANCE-Core-Coil-Ballast-71A2571-001D-100W-H38-H44-Mercury-120-277V/154303647148

The first two are fluorescent ballasts that should make 100W. Not sure which ones better for a 100W mercury though (VHO or HO).
The last one is an ACTUAL mercury vapor ballast. Not super cheap cause I'd need two of them. The main thing though is that it'll be even more expensive because I will need enclosures. The first two are pretty much plug and play.

Can anyone comment if they have tried a high output T12 ballast on 100W mercury?

Funkybulb and joseph_125 have ran North American 100w H38 mercury vapor lamps on F84T12/F96T12 HO magnetic fluorescent tube ballasts without any issues. They simply used one red and one blue output wire to drive the lamp.

I didn't realize you can run a mercury vapor bulb on a fluorescent ballast

I didn't realize you can run a mercury vapor bulb on a fluorescent ballast

In the UK, it was actually common to run high wattage fluorescent tubes off low wattage mercury vapor ballasts and low wattage mercury vapor lamps off high wattage fluorescent tube ballasts.

Very interesting. I wonder if I could turn a 400w mh ballast into a step up transformer for 277v

In the UK, it was actually common to run high wattage fluorescent tubes off low wattage mercury vapor ballasts and low wattage mercury vapor lamps off high wattage fluorescent tube ballasts.

Actually, what happened was this. After World War 2 there was not much money available to develop fluorescent lamps in the UK, so tubes were designed specifically with the same electrical characteristics to run from 80W and 125W MV ballasts, which  already existed. This was also the reason that BC bayonet caps were used on these early tubes, as it was cheaper than modifying equipment to make bi-pin caps.

Very interesting

Actually, what happened was this. After World War 2 there was not much money available to develop fluorescent lamps in the UK, so tubes were designed specifically with the same electrical characteristics to run from 80W and 125W MV ballasts, which  already existed. This was also the reason that BC bayonet caps were used on these early tubes, as it was cheaper than modifying equipment to make bi-pin caps.

I heard it was mainly during the war (and not after), when this way mainly the engineering resources (what would be needed for all the retooling) were saved to work on the war projects instead...
And the fluorescents with their efficacy and light character were needed mainly in the industry, where the higher wattage was just matching the need...

@Medved - You're probably right, I suppose. I wasn't around at the time