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#128251 - 12/18/02 05:30 PM voltage to ground
Cindy Offline
Member

Registered: 06/23/01
Posts: 196
Loc: PDX, OR, US
sorry another dumb question guys
voltage to ground in 110.26 table
208 is only between phases, right?
240 is only between phases, right?
480 is where I get lost, delta, Y, ungrounded and grounded

i figured out that i was still having trouble with this when i looked at 2 AH units on a roof that were about 2 feet apart. there are doors between them with controls inside and i dont remember if it was 208 or higher, but it bothered me that i didn't know which column applied in the 110.26 table, over 150v or not

so here i am, any help? diagrams on-line or simple explanations wanted, thanks

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#128252 - 12/18/02 05:42 PM Re: voltage to ground
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
208Y/120V is <150V-to-ground.

240∆ is considered >150V-to-ground, as is 480Y or ∆.




[This message has been edited by Bjarney (edited 12-18-2002).]

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#128253 - 12/18/02 05:46 PM Re: voltage to ground
Cindy Offline
Member

Registered: 06/23/01
Posts: 196
Loc: PDX, OR, US
thanks Bjarney, so what they mean by 'volts to ground' is not phase to ground?

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#128254 - 12/18/02 05:53 PM Re: voltage to ground
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
AFAIK, they are considered the same with respect to this Code section.

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#128255 - 12/19/02 06:20 AM Re: voltage to ground
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
See the definition in Article 100.
 Quote:
Voltage to Ground. For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit.
_________________________
Don(resqcapt19)

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#128256 - 01/05/03 04:21 AM Re: voltage to ground
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Cindy,

Not a "Dumb Question" at all!

Simple answers:

For Grounded Systems; The highest Voltage between an Ungrounded Conductor and the System's Grounded Conductor equals the "Potential To Ground" (Voltage To Ground)
Example Systems:

120/240 VAC 1 Phase 3 Wire - grounded center tap: Voltage to ground = 120 VAC (< 150 VAC),

208Y/120 VAC 3 phase 4 Wire Wye: Voltage to ground = 120 VAC (< 150 VAC),

120/240 VAC 3 phase 4 Wire Delta: Voltage to ground = 120 VAC (on 1 phase 3 wire circuits), 208 VAC for L-L / 3 phase circuits (> 150 VAC),

240 VAC 3 Phase 3 Wire Corner Grounded Delta: Voltage to ground = 240 VAC (> 150 VAC),

480Y/277 VAC 3 Phase 4 Wire Wye: Voltage to ground = 277 VAC (> 150 VAC),

480 VAC 3 Phase 3 Wire Corner Grounded Delta: Voltage to ground = 480 VAC (> 150 VAC),

600 VAC 3 Phase 3 Wire Corner grounded Delta: Voltage to ground = 600 VAC (> 150 VAC).

For Ungrounded Systems:
"At Least" the L-L Voltage would be considered the Voltage to Ground.
Actual Voltage to Ground - as applied across an unintentional connection (AKA Personnel), is what Potential Difference is required to push a current across an Impedance (resistance of the unlucky person + the reactance between the circuit and the transformer) via the Capacitively Coupled Circuit.

As you know, many long winded threads have been posted here discussing this, so no need for me to blow out more baloney!

Scott s.e.t.
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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