How can I run my 480 volt streetlights? I don't want to change out the ballasts, and I also don't have a transformer.

You could use the 480V tap on another multi tap ballast. Not very efficient, but would get the job done. I believe the multi tap "step up" ballast must be equal or of greater wattage than your street light.

What wattage are you trying to run ? and is it just to see them work or are you going to run them long term ?

You could use the 480V tap on another multi tap ballast. Not very efficient, but would get the job done. I believe the multi tap "step up" ballast must be equal or of greater wattage than your street light.

I don't have any other streetlights with 480v taps, and I also don't have any with higher wattage ballasts.

What wattage are you trying to run ? and is it just to see them work or are you going to run them long term ?

They're 400 watts, and I just want to maybe install them outside, once I find out a good way to connect them to a photocell.

Anything long term your going to need a step-up transformer and I would just remote mount the photo cell and run them as a group of lights, keep in mind 480 is lethal, but honestly getting that size transformer your better off getting a 120 ballast, I don't want to sound like a wet blanket but it's a cheaper more efficient and safer 480 is for roadways and large parking lots where you need to go the distance and keep the copper costs low.. But if your going to do it make sure the wire you use is rated for at least 600 volts ( most big box stores only sell 300 volt stuff )

And you could more then likely rewind a microwave transformer to output enough to run a single lamp at a time..   

Keep in mind 120V is LETHAL as well-more people are killed from it than 480V.I also have the same problem-a streetlamp fixture that has a 150W HPS S55 ballast that needs to run from 480V only.I am still looking for a transformer.That is the best way.

120 is lethal but 480 is whole different kettle of fish, you can't safely use big box hardware so things like light switches, contacts, circuit breakers or wire that would otherwise be considered safe with 120/240/277..

And the only reason more people are killed or injured by 120 is because you can't get 480 in a residential application, and commercial places hire trained electricians...    

For the voltage to be lethal you have to touch it. Dont do it and 480V will be as safe as 120V or any other voltage

In the 1900s Edison had an argument against Tesla/Westinghouse of how AC is more dangerous. Except that the problem was not the AC, but the way how Edison designed his appliances :

https://www.terapeak.com/worth/antique-ge-edison-electric-co-hotpoint-art-deco-toaster-early-1900-039-s-working/172246349782/



We occasionally use "125V 15A" rated components of stuff imported from the US (power cables, plugs, switches, ....) at 230V, and i have never seen any problem with that

It really depends only on the clearance between current carrying conductors, and for something like a switch, the current they break (so size of arc). If the switch controls a light load it will handle 230V just fine, as the arc when opening the light load is small. If the clearance is too small to handle 230V safely, then it is too small for 120V as well (consider that every 120V installation can normally have surges well exceeding 230V)

The clearance between conductors and the outside of the device is normally very good (as in an 120V switch with only the Plastic handle coming out). This sort of clearance would hold well over a kV



Get 480V by using 2 120V/240V step up autotransformers (as used for for foreign appliances) - Plug them into 2 opposite legs of the supply, then each one puts out 240V, between them there will be 480V

For the voltage to be lethal you have to touch it. Dont do it and 480V will be as safe as 120V or any other voltage

In the 1900s Edison had an argument against Tesla/Westinghouse of how AC is more dangerous. Except that the problem was not the AC, but the way how Edison designed his appliances :

https://www.terapeak.com/worth/antique-ge-edison-electric-co-hotpoint-art-deco-toaster-early-1900-039-s-working/172246349782/



We occasionally use "125V 15A" rated components of stuff imported from the US (power cables, plugs, switches, ....) at 230V, and i have never seen any problem with that

It really depends only on the clearance between current carrying conductors, and for something like a switch, the current they break (so size of arc). If the switch controls a light load it will handle 230V just fine, as the arc when opening the light load is small. If the clearance is too small to handle 230V safely, then it is too small for 120V as well (consider that every 120V installation can normally have surges well exceeding 230V)

The clearance between conductors and the outside of the device is normally very good (as in an 120V switch with only the Plastic handle coming out). This sort of clearance would hold well over a kV



Get 480V by using 2 120V/240V step up autotransformers (as used for for foreign appliances) - Plug them into 2 opposite legs of the supply, then each one puts out 240V, between them there will be 480V

Actually you can touch it, I've grabbed a 600 volt line and there was no ill effect, you actually have to complete the circuit, And we are not going from AC to DC we are going from a low potential to a much higher potential now going from 120 to 480 are you willing to bet your life on a piece of plastic not rated for it ? then lets add wet or damp hands into the mix, and get ready to pay for a 480 volt GFCI/RCD (might as well buy brand new lights it will be cheaper) still willing to bet your life on it, just because something works for now doesn't make it safe if your installing a 480 volt circuit you need to be safe and do it right, this is why you can't get 480 in a residential setting, even if your in a multi-unit high rise between the phases you can't get it, in the USA it's 277 and Canada its 347 and the UK is what 400... 

And pretty much all the US stuff is generally rated to 277 things like light switches, plugs and cords, even the cheap NMD wire is 300 volt so they are safe to use on 240..

And please don't take it the wrong way, I get it they are new ballasts and I know they are like me and want to fire them up, I would, and use them and I'm sure they will last way longer then a used ballast of unknown origins, but even just the cost of getting a 120 to 480 or two 120 to 240 transformers is at least double what you can get a good used 400 watt ballast if not more, and with a 120 volt ballast they are free to use a nice photocell and easier to source parts so it's a win they get a beautiful new light and know it safe at the same time, even it it has a used ballast in.. 

But on a side note you can get 480/240 to 120 Control transformers used fairly cheap just make sure the VA rating is high enough..
 

Voltage is between 2 points, so "touching voltage" means touching the 2 points..

Its not a matter of AC vs DC, but of why we consider some voltage dangerous. It is dangerous if you get connected across it

Edison was bragging about how DC is safer, as his appliance designs were as dangerous as 1890s/1900's appliances get. Its only later that "electrical safety" became about preventing contact with live conductors, instead of about having less lethal voltage on them



And preventing contact with live parts is done differently in different cases..

This is a ballast testbench setup. Safety on the test bench is based on not poking hands into exposed live parts

In everyday use setups, we want something that is safe even when we are not as cautious with it. Safety there is based on suitable enclosures, IP levels, double isolation, RCDs and so on



A few mm (or much bigger !) Plastic part is good isolator unless made for special purpose of conductive materials. You can absolutely trust it for low voltages like 120, 240 and even 480V

In this case, the switch handle is definitely made of isolating material, and by itself would hold up to much higher voltages than rated between the switch contacts inside and your hand outside

With switch / plugs ect, the limiting factor is the arc between the open contacts or from them to the switch frame, not breakdown through the Plastic of the handle. The arcing depends on the load current as well as on voltage. 120V 15A rated switch will work just fine switching a tiny resistive load at 480V, and fine with most loads at 230V. Yet it will weld in a single operation (and possibly even with arc reaching out through the hole around the handle...) when closed into a short circuit at 120V....

Honestly, there is nothing wrong with 480 volts if done correctly. 

Also to clear up some misconceptions:


"But if your going to do it make sure the wire you use is rated for at least 600 volts ( most big box stores only sell 300 volt stuff )"

Most big box stores carry THHN/THWN which is rated 600 volts. 


 "you can't safely use big box hardware so things like light switches, contacts, circuit breakers or wire that would otherwise be considered safe with 120/240/277"


Most of those aren't technically rated 240 and 277 volts either. Most 99 cent switches are 120 volts only and residential circuit breakers are only rated 120 volts across their poles. But that should not matter because you should only be switching the 120 volt supply to your step up.


"And the only reason more people are killed or injured by 120 is because you can't get 480 in a residential application, and commercial places hire trained electricians..."

A lot of places use in house maintenance. In fact its the reason why the NEC is being "dumbed down" (ie ballast disconnects) to protect these unqualified people.


"In the 1900s Edison had an argument against Tesla/Westinghouse of how AC is more dangerous. Except that the problem was not the AC, but the way how Edison designed his appliances :

https://www.terapeak.com/worth/antique-ge-edison-electric-co-hotpoint-art-deco-toaster-early-1900-039-s-working/172246349782/ "

My reply to this is somewhat off topic, but it wasn't just Edison. Up into the 70s you could still buy metal framed 2 prong appliances like drills which leads to electrocutions. Which leads me to my point: ground the fixture and and don't contact any internal parts and it will be as safe as 120 volts.       
 

Cables that have visually thick isolation can handle at least few 100's V regardless of their ratings

For the record, a double isolated smoke alarm cable (not rated for any voltages at all, intended for 12V) handles 230V and output of electronic Fluorescent ballasts (up to 400V) just fine. "600V" rated cable handles HID ignitor output (multiple kV) intermittently, though it may noy hold it continuously for very long

This may not be suitable for permanent installation, but fair enough to use on the testbench



The problem with that toaster is the fact that when you open the side walls (to get the bread in or out) the heating element is right there fully exposed for accidental touching. Its not like modern toaster where you have to poke your hands much deeper inside

The concern for dangers that only appear in case of isolation fault towards the metal body, and the introduction of Protective Earth, came much later

All true and well said Ash 

These lights are going outside so it's considered a permanent installation, or at least that is what the insurance adjuster will consider it to be and the local authorities, so it should be done to code, and yes anything will work on the test bench even CAT 5 will handle 480 but the test bench is not permanent, and you could use a 120 to 30 volt transformer and simply apply 120 to the 30 volt side, it would work on the test bench but its not for a permanent or semi-permanent install, so what I'm getting at it do it correctly and personally I'd rather talk to Wattmaster, then talk about him because he didn't do it correctly, things like fires and electric shocks aren't fun and games, so what is about the easiest, safest and cheapest solution is to get a used 480/240 to 120 control transformer in a 500 VA or higher and mount it in the light fixture if there is room or an outdoor rated box close to the light and do everything in either 120 or 240 upto the control transformer and the 480 is only going from the transformer to the light so it's safely out of reach and yes you can use THWN but not THHN as THHN is for dry locations only..   

Personally I'd just change the ballast.... And I've been shocked a plethora of times by both 120 and 240v... Nothing wrong with me as far as I can tell well, maybe a few memory issues.. But then again always had those, I might add two of those incidents were circuit completions between both hands, those were only 120v the 240v was once because I was drinking a bottle of water and spilt it around unplugging a dryer, I'm younger and lucky, been smarter since then, when I'm older I'm sure that will knock me on my arse dead.

Don't be picky man, just change the ballast, don't get killed or waste money because your being picky about what ballast you never see anyway is powering the lamp, don't mean to be blunt about it but yeah...