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#184299 - 02/06/09 01:46 PM CT cabinet with only 2 CT's in it
trekkie76 Offline
Member

Registered: 06/19/04
Posts: 219
Loc: baileyville, maine, usa


I found this photo on the internet and am wondering why 2 things.

1. Why is there only 2 CT's, with the B phase unmetered?
2. If the color code is right, this is a 208Y/120V 4 wire system. Where is the grounded(neutral) conductor? Isn't this a violation of 250.24(C)?
I have never seen a CT cabinet that didnt have a CT for each phase. Maybe someone could steer me in the right direction.
Thanks,
Gary
Edited to add code section


Edited by trekkie76 (02/06/09 01:51 PM)

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#184301 - 02/06/09 02:53 PM Re: CT cabinet with only 2 CT's in it [Re: trekkie76]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Disregarding the 'color code'.....600 volt fuses in disco, looks like 3 phase, 3 wire (delta) 480 volt service.

I only came accross this twice, a long time ago; industrial
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#184302 - 02/06/09 03:24 PM Re: CT cabinet with only 2 CT's in it [Re: trekkie76]
Happy Birthday LarryC Offline
Member

Registered: 07/05/04
Posts: 776
Loc: Winchester, NH, US
Corner grounded Delta system?

Larry C

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#184306 - 02/06/09 04:45 PM Re: CT cabinet with only 2 CT's in it [Re: LarryC]
Trumpy Offline

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Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Shouldn't that CT enclosure and the meter base enclosure also have a ground wire attached to them and run back to that ground wire in the Disconnect?
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#184307 - 02/06/09 05:25 PM Re: CT cabinet with only 2 CT's in it [Re: Trumpy]
JoeTestingEngr Offline
Member

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
Whether corner grounded or not, don't 2 CTs give you all you need on a delta??? Not true with a wye.
Joe

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#184309 - 02/06/09 05:59 PM Re: CT cabinet with only 2 CT's in it [Re: JoeTestingEngr]
ameterguy Offline
Member

Registered: 05/17/02
Posts: 33
Loc: Mass
A Delta service is metered with two CTs. The service being either corner grounded or not, does not change the metering setup.
The picture also shows a three phase, four wire meter socket. I think either the CT configuration is wrong or the socket is wrong.

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#184326 - 02/07/09 03:34 AM Re: CT cabinet with only 2 CT's in it [Re: ameterguy]
frenchelectrican Offline

Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
The only other possiblty when you see two CT's there it possbilty that is used for electric motor load only { I did see it in few place like that however POCO don't like it much }

Merci,Marc

P.S. look like 60 a 240 or 208 volt otherwise 480 v 30 amp due the conductor size looks pretty small.


Edited by frenchelectrican (02/07/09 03:37 AM)
Edit Reason: add more info
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#184328 - 02/07/09 09:52 AM Re: CT cabinet with only 2 CT's in it [Re: frenchelectrican]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Looks like max 30 amp fused disco at 480/600 volt as I look again.

POCO here supplies CT's and meter pan, and installs wiring from CT's to pan.
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John

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#184340 - 02/07/09 01:08 PM Re: CT cabinet with only 2 CT's in it [Re: HotLine1]
RODALCO Offline
Member

Registered: 12/08/05
Posts: 863
Loc: Titirangi, Akld, New Zealand
It looks like an overkill to me for CT metering.
That size cable looks like 16 or 25 mm˛ and the power usage could have been metered directly with a whole current meter.

This CT set up adds hugely to the overall installation costs.
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