Parking lot 220v no neutral

[petroc]

Put up a lamp post and didn't realize standard base sockets and 120v , have only 208v no neutral and cant pull new one wire. new fangled LED bulbs advertise they work on 120v-277v. Will they work when its two live conductors and no neutral return path? Cant find a real answer. I guess i could get a 1 kva transformr that could fit in the hand-hole but I'd rather use these bulbs if they will actually work. Any buddy care to teach an older electricain about this new tech. I dont trust the sales people who say they will work.

 

[LarryFine]

Will they work when its two live conductors and no neutral return path?

Absolutely, yes. Just be sure the socket shell conductor (white) is fully insulated.

 

[petroc]

Absolutely, yes. Just be sure the socket shell conductor (white) is fully insulated.

Thank you Larry gonna give it a shot. Easier then squeezing a transformer into the vault.
And i get it make sure the old neutral is in good shape

 

[LarryFine]

And i get it make sure the old neutral is in good shape

Exactly. Intact insulation, nothing more. Any disconnect should be 2-pole, of course.

 

[infinity]

So the supply voltage is 208 volts? Your thread title mentioned 220.

 

[LarryFine]

 

[kwired]

I don't fully understand how they work but what I have figured out is the front end of the circuitry is a rectifier that can take the rated input voltage range so anything between 120 and 277 VAC is acceptable. They then use similar methods a VFD uses to convert the DC bus voltage to the output voltage needed for the load. If you have a driver with 0-10V dimming ability - this is sort of no different than giving a VFD a signal to change the output characteristics.

 

[SceneryDriver]

I don't fully understand how they work but what I have figured out is the front end of the circuitry is a rectifier that can take the rated input voltage range so anything between 120 and 277 VAC is acceptable. They then use similar methods a VFD uses to convert the DC bus voltage to the output voltage needed for the load. If you have a driver with 0-10V dimming ability - this is sort of no different than giving a VFD a signal to change the output characteristics.

LED "bulbs" are constant current. They typically have a full wave rectifier and filter cap ahead of a purpose-designed constant current regulator chip. That chip sets the current through the series connected LED chips.

As long as you have sufficient voltage present to overcome the forward voltage drop of the series-ed LED chips, they will operate on almost any voltage (up to a limit of course).

Phase Control dimming still gives you the needed peak voltage to overcome the forward voltage drop of the LED strings, but delivers less total power, so it appears dimmer. Some of the driver chips can't deal with the dimmed power, and don't behave well.



SceneryDriver

 

[zbang]

Will they work when its two live conductors and no neutral return path?

As long as there are two conductors that can form a complete circuit with the appropriate voltage, it doesn't matter whether one is a neutral or not.

 

[oregon]

I ran across some retrofitted MH cobras where they left the MH ballast in place, but removed the caps. Somehow that old ballast was dropping the voltage to a perfect 120V

 

[LarryFine]

I ran across some retrofitted MH cobras where they left the MH ballast in place, but removed the caps. Somehow that old ballast was dropping the voltage to a perfect 120V

Most HID ballasts are simple multi-tapped auto-transformers without the caps.

 

[Flicker Index]

I ran across some retrofitted MH cobras where they left the MH ballast in place, but removed the caps. Somehow that old ballast was dropping the voltage to a perfect 120V

Mercury vapor and non instant-strike MH go dark for some 10 minutes if there's a power blip. Aside from 120v operation, that 120v is used to power an incandescent backup for such occasions to avoid total darkness.