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#115174 - 08/22/03 10:09 PM "Tech Power"
Admin Offline


Registered: 10/07/00
Posts: 3184
Loc: NY, USA
From the 'EMail' Bag:

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!

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#115175 - 08/23/03 04:17 AM Re: "Tech Power"
electure Offline


Registered: 12/24/00
Posts: 4229
Loc: 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 09:34 AM Re: "Tech Power"
Ryan_J Offline

Registered: 08/19/03
Posts: 1355
Loc: 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 01:07 PM Re: "Tech Power"
Electricmanscott Offline

Registered: 01/12/02
Posts: 1478
Loc: Holden, MA USA
I wonder what the cost difference is between this and a ready made unit like an Equitech?

#115178 - 08/23/03 10:03 PM Re: "Tech Power"
frank Offline

Registered: 05/29/01
Posts: 373
Loc: 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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