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Joined: Jan 2005
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Cat Servant
Scott, here in Nevada the state limits us to "work within our classification."

Local towns have their own understanding on this issue. While Reno will accept an EC'c calculations to 400 amps, neighboring Sparks lets us go to 800.
It has been speculated that these levels are based upon:
-400 amps is the largest service we can have without requiring CT's for metering; and,
-800 amps is the PoCo limit for single phase services.

Which brings us to the ultimate AHJ- the PoCo. All new services, and service upgrades, ned to be reviewed, and inspected, by them. Chances are, anything the PoCo has signed off on will be approved by the locality.

Oh, and Iwire... you're right, my attitude is influenced by local conditions. 480 is pretty rare here, and the PoCo has a strong "you don't need 480" bias. Indeed, getting real three-phase can be a challenge!
To give an illustration.... the vast majority of sparkies I've met have no idea what a "delta" system is, or a "corner grounded," - though there are quite a few in the area. These guys have never noticed a service where the voltage to ground was different for different legs- all their measurements have been leg-to-leg!

In an even worse manner, maintenance folks are seriously under-trained and inexperienced. This is what you get when your town lacks any serious industry.

[This message has been edited by renosteinke (edited 07-08-2006).]

Joined: Jul 2004
Posts: 625
Reno, what do they supply to the big casinos/hotels? Surely it's not 208/120 at a bazillion amps?

Joined: Jan 2005
Posts: 5,362
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Cat Servant
Actually, they do something like that, at most of them....

The PoCo will deliver high voltage to transformers within the casino, where it will be stepped down to 208.

One twist on this is that, to discourage unqualified servicing of the equipment, several casinos have "Danger 480" stickers on the 208 equipment!

The problem has another, uglier, face. Supply houses don't stock all that much in the way of 480 gear (and they charge dearly for it).... so I HAVE found 480 installed using 250-rated disconnects.

[This message has been edited by renosteinke (edited 07-09-2006).]

Joined: Aug 2001
Posts: 599
The big casino's in Vegas have large central plants where they receive the standard distribution voltage (12-13KV)from the utility. The huge casino's receive transmission level voltage (69KV) at their central plants where it is stepped down to 12KV. At any rate the power company meters at the 12KV or 69KV in the CP substation then the casino's distribute their own, load side of the meter, 12KV class system. Usually 12,470V, to many unit substations around the casino. Some are 12.47KV-480/277 some are 12.47KV-208/120V.

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