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10-04-2012, 10:00 PM   #1
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## 208 voltage

how can you tell what is 208 voltage 120 voltage is a black hot wire and a white neutral wire and 240 voltage is two hot wire black and red or black and white as hot what is 208 voltage

10-04-2012, 10:10 PM   #2
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208 volts is 120x1.732. In a wye transformer Line voltage(208) = phase voltage(120) x 1.732. Generally Red, Black, Blue are the colours. You get 208 volts when you go accross any 2 phases in a 120/208V system.

In a 3 wire system, you typically have 2 lines (red and black with 240V across them) with a centre tapped neutral from a 3 phase delta source.

Last edited by AltaSparky; 10-04-2012 at 10:19 PM.

10-04-2012, 10:18 PM   #3

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Quote:
 Originally Posted by astovall7 how can you tell what is 208 voltage 120 voltage is a black hot wire and a white neutral wire and 240 voltage is two hot wire black and red or black and white as hot what is 208 voltage
Is there a question in this confusing series of words?
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 10-04-2012, 11:31 PM #4 Member     Join Date: Apr 2011 Location: Almost Arkansas Posts: 2,764 Rewards Points: 2,000 how can you tell when a sentence begins or ends without punctuation and capital letters this may be a sign of apathy or ignorance is there a way to function properly without these in a structured forum i do not have the answer............. __________________ Do you want it your way or the right way?
 10-05-2012, 06:01 AM #5 Member     Join Date: Jan 2008 Location: Long Island Posts: 3,630 Rewards Points: 2,000 120V can range from 115V thru 125V and the Single phase as it is called can be 200V thru 240V depending on the "gods generators".see those transformers up on the poles they are being supplied 12,000V whick is split up around the neighborhood.colors are standard you mentioed but never take it for granted always check to ground all wires and between each other...especially when your up on a ladder.... __________________ http://www.youtube.com/watch?v=U1qEZHhJubY
 10-05-2012, 06:11 AM #6 Licensed Electrician     Join Date: Mar 2012 Location: SE Wisconsin Posts: 4,352 Rewards Points: 2,006 There is no NEC mandated color scheme for any system, however, most 208V systems are black, red, blue. __________________ __________________________________________________ ______________ Answers based on the National Electric Code. Always check local amendments.
10-05-2012, 05:10 PM   #7

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Quote:
 Originally Posted by Speedy Petey Is there a question in this confusing series of words?
I think he's young and just a few months or so out of an HVAC trade school. And doesn't know how to ask what he wants to know in an easy phrased question.

10-05-2012, 08:52 PM   #8
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Quote:
 Originally Posted by astovall7 how can you tell what is 208 voltage 120 voltage is a black hot wire and a white neutral wire and 240 voltage is two hot wire black and red or black and white as hot what is 208 voltage
Sometimes you cannot tell just by looking at it. You tell for sure by measuring it using a voltmeter.

A 120/208 system may look the same as a 120/240 volt system, wire colors and all. The 120/208 volt system is not common in homes but may be found in apartment complexes with mixed commercial use such as stores and restaurants ont he first floor and dwelling units upstairs.

In a 120/208 volt system you find only 208 volts where you would expect to find 240 volts (hot to hot such as black to red), and the 120 volts is found in its normal places (hot to neutral)

Now you may wonder how you can have exactly three wires, red, white, and black, in your power feed cable and you get 120 volts from red to white, 120 volts from black to white, and 208 volts from red to black. Shouldn't the last one be the sum of the first two? The answer requires understanding of what is means to be out of phase but not diametrically (180 degrees) out of phase. That mathematical discussion is too complex for me to include here. Superficially a 120/208 volt service has two of the phases of a 208 volt 3 phase system with a symmetric neutral aka a 208 volt Y (wye or star) 3 phase system.
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Last edited by AllanJ; 10-05-2012 at 09:05 PM.

10-05-2012, 08:55 PM   #9
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Quote:
 Originally Posted by AllanJ Sometimes you cannot tell just by looking at it.

Sometimes???? How about it's impossible to tell by looking at it.
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 The Following User Says Thank You to Missouri Bound For This Useful Post: jbfan (10-05-2012)
10-05-2012, 09:00 PM   #10

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Quote:
 Originally Posted by Missouri Bound Sometimes???? How about it's impossible to tell by looking at it.
When it says 120/208 on the panel box.

10-05-2012, 09:16 PM   #11
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Quote:
 Originally Posted by beenthere When it says 120/208 on the panel box.
You can't believe everything you read!
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10-05-2012, 09:28 PM   #12

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Quote:
 Originally Posted by jbfan You can't believe everything you read!
LOL, that is true.

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