# Thread: Difference between 120V & 208V?

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## Difference between 120V & 208V?

As stated on the title. I'm confused about power..

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120 = 1 120 v hot leg + neutral leg + ground leg
208 = 2 120 v hot legs + ground leg

when you put a volt meter between the 2 hot legs you get 208 volts total out of the 2 120 volt legs.

Its more efficient.

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So in other words, 1amp at 208V is equivalent to 2amps at 120V?

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P = IV

Simple physics

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Originally Posted by LaptopFreak
So in other words, 1amp at 208V is equivalent to 2amps at 120V?
almost - its very close - its 87% of 2 120 v circuits but you pick up some efficiencies etc - so I usually count it as doubling it.

plus your power supplies will last longer and you dont use as much copper to deliver the higher power.

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Also, most of your equipment will run 208v with the exception of some old legacy systems or old dial up modems. So you should not have any problems with 208v, it's just a lot more efficient system.

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Originally Posted by ServOnDemand
Also, most of your equipment will run 208v with the exception of some old legacy systems or old dial up modems. So you should not have any problems with 208v, it's just a lot more efficient system.
brings up a thought - some equipment will require you to change a manual selector switch on the psu - others will be autoranging.

just make sure you have the right power cords.

<<snipped>>
Last edited by Chris_M; 08-31-2009 at 11:49 AM. Reason: removed fluff

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Note the following distinction:

240v - 2 hots on same phase (120*2)
208v - 2 hots on separate phases (120*2*1.73)

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Originally Posted by Jay Suds
Note the following distinction:

240v - 2 hots on same phase (120*2)
208v - 2 hots on separate phases (120*2*1.73)
Great point
Just to clarify the point Jay made, 1.73 is the square root of 3, the full formula is 120v*2*sqr3)

Great chatting with you at the show Jay!

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Originally Posted by Jay Suds
Note the following distinction:

240v - 2 hots on same phase (120*2)
208v - 2 hots on separate phases (120*2*1.73)
So in other words, 2 x 240V is equivalent to 4 x 120V both at the same ampere right?

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What is 3 phase power?

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Originally Posted by skullbox
What is 3 phase power?