Why 277 volt lighting

[kwired]

Anyways, can you give me a scenario regarding 480 volt arc flash and linemen?

Many POCO's safety practices sort of eliminate those from happening.

They usually kill the transformer before doing any work on secondary, or if a self contained meter they may require a line side disconnect to be opened before working in the meter socket. Beyond those activities that they don't encounter 480 volts as often as 250 and below.

250 and below they will have a transformer supplying multiple customers quite often and if they can won't interrupt one while working on something that supplies another customer.

480 volt services is often supplying one service. If you are going to have to do a task that interrupts any conductor chances are you at least want to turn off the main regardless. If only supplying one customer then if you are killing their main, why not kill the entire secondary before working on it? reduces the risk of injury.

 

[kwired]

Good point. UK is 230V/400V.

do you have lighting that operates 400V or is it all 230V?

 

[mbrooke]

Many POCO's safety practices sort of eliminate those from happening.

They usually kill the transformer before doing any work on secondary, or if a self contained meter they may require a line side disconnect to be opened before working in the meter socket. Beyond those activities that they don't encounter 480 volts as often as 250 and below.

250 and below they will have a transformer supplying multiple customers quite often and if they can won't interrupt one while working on something that supplies another customer.

480 volt services is often supplying one service. If you are going to have to do a task that interrupts any conductor chances are you at least want to turn off the main regardless. If only supplying one customer then if you are killing their main, why not kill the entire secondary before working on it? reduces the risk of injury.

Agree. Though under 150 volts to ground you typically get a smaller bank, over 150 your bank is such that shoart circuit amps exceed what you typically get at 120/208Y.

 

[mbrooke]

And I just want to clarify that my statement above speaks in terms of median probability. On average there are more 100,000AFC 480 volt services than 120/208 volt services.

 

[Besoeker3]

do you have lighting that operates 400V or is it all 230V?

All 230V as far as I'm aware.

 

[mbrooke]

All 230V as far as I'm aware.

No 400 volt lighting for ball fields and stadiums?

 

[kwired]

All 230V as far as I'm aware.

I think 480 volt lighting was nearly non existent here other than for some HID lighting. But now I believe you are finding LED coming that way probably so it can replace those existing 480 units more so than they otherwise would have designed them for 480 if there were none to replace.

 

[kwired]

No 400 volt lighting for ball fields and stadiums?

Run "full boat" to top of pole. Yes you have one more conductor, still have same max kVA.

 

[Electricmo]

Thanks for proving me right.

Anyways, can you give me a scenario regarding 480 volt arc flash and linemen?

First off arc rated fire retardant clothing required. Rubber gloves and PPE required.
All equipment deenergized and grounded if working on 480. All meters here have potential transformers reducing voltage in socket. All 480 volt meters that I know of are bolt in requiring disconnecting power before pulling/ connecting. We never work on energized panels as clearence tolerances to close. Testing voltage with rubber gloves is extent of what we do hot. 480 volt arc flashes are nasty and damaging. I don’t think I would want it in a light fixture unless it is clearly marked as such and it should NEVER be worked on energized and I don’t care who you are.

 

[Electricmo]

Check this out.

 

[Besoeker3]

No 400 volt lighting for ball fields and stadiums?

HID - I forgot about that. Silly me.

 

[mbrooke]

First off arc rated fire retardant clothing required. Rubber gloves and PPE required.
All equipment deenergized and grounded if working on 480. All meters here have potential transformers reducing voltage in socket. All 480 volt meters that I know of are bolt in requiring disconnecting power before pulling/ connecting. We never work on energized panels as clearence tolerances to close. Testing voltage with rubber gloves is extent of what we do hot. 480 volt arc flashes are nasty and damaging. I don’t think I would want it in a light fixture unless it is clearly marked as such and it should NEVER be worked on energized and I don’t care who you are.

Right- so what difference would 480 volts make at a light fixture?

 

[kwired]

First off arc rated fire retardant clothing required. Rubber gloves and PPE required.
All equipment deenergized and grounded if working on 480. All meters here have potential transformers reducing voltage in socket. All 480 volt meters that I know of are bolt in requiring disconnecting power before pulling/ connecting. We never work on energized panels as clearence tolerances to close. Testing voltage with rubber gloves is extent of what we do hot. 480 volt arc flashes are nasty and damaging. I don’t think I would want it in a light fixture unless it is clearly marked as such and it should NEVER be worked on energized and I don’t care who you are.

But keep in mind you are typically working on/near the source where there is more available fault current.

A 14 or 12 AWG conductor at the luminaire doesn't have the same available fault current. Bigger issue with luminaires and 277/480 seems to be electrocutions NEC helped this by requiring luminaire disconnects a while back.

 

[mbrooke]

Check this out.

Yup, that can happen at any voltage. At certain fault levels a bear suit simply provides the option of an open casket funeral.

But again I'm having trouble seeing how this applies to lighting branch circuits.

 

[Electricmo]

I would think that possibly there is a added expense to produce 480 volt fixtures that doesn’t generally give a good return on your investment. Maybe it’s cost effectiveness doesnt warrant the expense of producing it. The only place it would be used is in buildings or businesses that have it available.

 

[mbrooke]

I would think that possibly there is a added expense to produce 480 volt fixtures that doesn’t generally give a good return on your investment. Maybe it’s cost effectiveness doesnt warrant the expense of producing it. The only place it would be used is in buildings or businesses that have it available.

That could be it.

Does the NEC restrict 480 volt lightning in buildings?

 

[ActionDave]

That could be it.

Does the NEC restrict 480 volt lightning in buildings?

What difference does it make? They're wrong about everything.

 

[kwired]

I would think that possibly there is a added expense to produce 480 volt fixtures that doesn’t generally give a good return on your investment. Maybe it’s cost effectiveness doesnt warrant the expense of producing it. The only place it would be used is in buildings or businesses that have it available.

Well if 277 is available most the time so is 480.

I once did connect some HID's that the guy purchased used (probably real cheap) but come to find the ballasts only configured with 277 leads only, I used buck/boost to get him ~277 from 240.

 

[kwired]

That could be it.

Does the NEC restrict 480 volt lightning in buildings?

NEC doesn't restrict lightning

 

[mbrooke]

NEC doesn't restrict lightning

I mean lighting.