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Why 277 volt, single phase on commercial fluorescent lighting?

Why 277 volt, single phase on commercial fluorescent lighting?

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  #1  
Old 11-10-05, 12:53 PM
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Why 277 volt, single phase on commercial fluorescent lighting?

I work on such lights, yet have never understood this. The bulbs used can be run on various voltages. The ones at this center I maintain use the T8 (1 inch) x 48 inch 32w bulb, with 3 or 4 bulbs per fixture.

There must be an advantage to this voltage...but what?
 
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  #2  
Old 11-10-05, 01:12 PM
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Originally Posted by Bonehead
There must be an advantage to this voltage...but what?
MANY more fixtures on the same 20 amp circuit as compared to a 120v circuit.
 
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Old 11-10-05, 02:01 PM
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Originally Posted by Speedy Petey
MANY more fixtures on the same 20 amp circuit as compared to a 120v circuit.
Ahhhhh.

I suppose that they don't use this for househod due to the danger, I presume? I know an electrician who got zapped with the 277 once while working with the fluorescent lights, and he said some chice words. His head was up above the drop ceiling and I think he arced something across the ceiling grid off that fixture.
 
  #4  
Old 11-10-05, 05:40 PM
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They don't use it at home because it not available at home. 277 volts is the voltage to neutral of 480 volt three phase system.

I Canada we use 347 volt ballasts which is derived from 600 volt three phase.
 
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Old 11-10-05, 06:35 PM
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Man! How many three light 32 watt lay-ins do you guys put on a 20 amp circuit?
 
  #6  
Old 11-10-05, 08:15 PM
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The 277 is a component of their 3-phase power, and as mentioned you can put more lights on smaller wire compared to 120. Fluorescent bulbs do not take line voltage directly, so it doesn't require "different" bulbs; the ballast has to be designated for 277 volts. Some will be so-called universal, where you can wire it for 120 or 277.
 
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Old 11-11-05, 05:16 AM
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I believe Boneheads title asked WHY they did this. I managed a Private Club with an attached rental hall. One of our members worked for the electric company and installed a step-down transformer (think thats what he called it) and did the hook-up. Our electric bill dropped. He DID advise me to inform anyone doing work on this electrical system about the 277.
 
  #8  
Old 11-11-05, 07:33 AM
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I thought the answer was clear as to WHY. In general, it is always more efficient to use a higher voltage for any application. The operation of any device, from a light to a motor, uses energy measured in watts. Watts = volts X amps. So a higher voltage, same watts requires less amps. This is where the efficiency comes in. Any system, including wire, has internal resistance. So of all the current (amps) flowing in the system, most is used by the device to produce light, motion, etc. but some of the amps are "wasted" producing watts in the form of heat, in the internal resistance. This is referred to as "IR losses".

This is the reason that the energy transmission lines on your street may be anywhere from 240 to 480 on up to the thousands of volts, and the big regional lines are in the millions of volts. Otherwise, the wires would have to be huge to handle the current.


SO, higher voltage is always better from that standpoint, but then from safety, insulation, etc standpoint compromises are made. In this country, it has been settled that 120 volts is that highest safe voltage for general residential use. 240 is available in your house for stove, etc. using much large connectors and receptacles. Other contries do use 240 for the general residential applications.

Since many commercial buildings have 3 phase power available for many reasons which we will skip over, someone figured out that Why not use that available 277 single phase for the lighting? We get the efficiencies discussed above, and because it's lighting in the ceiling, the average John Doe will never be involved with messing with the fixtures.
 
  #9  
Old 11-11-05, 09:13 AM
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You will not use less energy with higher voltage. You may get some slight savings due to efficiency, but not much.
You pay for watts, and a watt is a watt.
Yes, amperge is lower at higher voltage, but the lamps are still 32 watts each. This is what you pay for. This is why electric meters are called watthour meters.

The main savings is during construction. More fixtures on a circuit. Less wiring, less homeruns, less circuits, etc.
 
  #10  
Old 11-11-05, 09:26 AM
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Commercial and industrial customers who have 480Y/277 volt service have to install their own transformers (most often dry type units) to step the voltage down to 120 volts for regular receptacles for power tools and office equipment.
 
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Old 11-11-05, 04:47 PM
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Thi is quite interesting and informative.

Why is it that the MORE powerful the current in volts, the LESS wire size one needs? It sounds backwards. Yet, I know that from DC voltage...look at the size of the 12 volt cable at the battery compared to the spark plug cable (the actual wire IN the rubber insulation is quite skinny and may not even be wire at all, but rather some fiber material,) and high performance ignition systems may be up to 50,000 volts DC.
 
  #12  
Old 11-11-05, 05:06 PM
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Because the more volts the less amps (current) you need to make the same power (watts).
Watts = volts times amps Increase the volts and the amps decrease for the same watts. Wire size is rated to carry the amps. The insulation on the wire is rated for volts to prevent shorting between the wires.
 
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Old 11-11-05, 09:10 PM
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In your car: The important factor in the spark system is the VOLTS. You need lots of volts to get a spark to jump. Current requirement, and watts, is miniscule.

Now, the starter: this is a workhorse. You are talking lots of WATTS, so you will need big AMPS, especiall since the battery is only 12 volts.


I stand by my comment about efficiency of higher voltage, based on the IR losses. But I agree that in dollar terms this is minor, and it is the material savings and just convenience of smaller wires that is in play.
 
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