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#115174 - 08/23/03 01:09 AM "Tech Power"  
Admin  Offline

Joined: Oct 2000
Posts: 3,443
From the 'EMail' Bag:

[Linked Image]
Here's an interesting installation. This is a homeowner installed (he's an EE) balanced power system. It's based on a used 480v to 240vct dry transformer. It's running with a 240v primary to get a 120vct secondary. The center tap of the secondary is grounded yielding a 60-0-60v volt system. Of course this 10kva transformer is only good for 5kva in this configuration.

So the "neutral" although it's really no longer a neutral is at 60v above ground as is the hot. The secondary is protected through double pole breakers and there is a 60a SPA GFCI on the transformer secondary. As long as GFCI is used as well as double pole breakers, this system is apparently OK under a little referenced section of NEC??? Not sure if that applies to residential use however and this was not a permitted job. There are a few other requirements such as the outlets must only be in technical equipment areas and somehow labeled as non-standard power.

The owner here is using it to run his rather elaborate home theater system. He even has a computer floor in his equipment room! All those Ell's are poking into the rear of the main house panel on the other side of the wall.

OK, pick it apart!

Tools for Electricians:

#115175 - 08/23/03 07:17 AM Re: "Tech Power"  
electure  Offline

Joined: Dec 2000
Posts: 4,259
Fullerton, CA USA
This looks like a clean job, my guess is that it's here in So CA., (due to the garage vent and an all-in-one service).
Article 647, though, which is a new one from the '02 Code, provides a limitation.
647.3(1) "The system is installed only in commercial or industrial occupancies".

#115176 - 08/23/03 12:34 PM Re: "Tech Power"  
Ryan_J  Offline
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
110.26 for the transformer encroaching into the working space of the disconnect.

Ryan Jackson,
Salt Lake City

#115177 - 08/23/03 04:07 PM Re: "Tech Power"  
Electricmanscott  Offline
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
I wonder what the cost difference is between this and a ready made unit like an Equitech?

#115178 - 08/24/03 01:03 AM Re: "Tech Power"  
frank  Offline
Joined: May 2001
Posts: 376
windsor ontario canada
I have to ask why install this in a house?Sort of looks like a LIM system at.21ma

[This message has been edited by frank (edited 08-24-2003).]

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