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#215025 02/22/15 06:59 PM
IMG_1237.JPG
Joined: Apr 2002
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What's behind the door???

Found doing a walk-thru on a complaint
Have to check this out further next week.
13 Comments
Joined: Apr 2002
Posts: 7,288
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OK, it's back to the sideways pics!!!


(Fixed - Admin)

Last edited by Admin; 01/24/17 08:00 PM.
Joined: Jul 2004
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G
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I haven't got to OMG yet. How was the 250 stuff?


Greg Fretwell
Joined: Oct 2000
Posts: 2,722
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John,

Is this supplied by a 1 Phase 3 Wire System, or a 3 Phase 3 Wire Corner-Grounded System?

BTW, Notice that most of the Grounded Conductors for the Branch Circuits are Fused.
The only one that is not Fused is at the bottom of the Bus Kit.

Nevertheless, quite a find!!! thumbs clap

--Scott (EE)


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Apr 2002
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I have to look at this in more detail.
It looked like the neutrals are all fused, except the tap off of the top buss.

It's in an old school bldg. More to come.


John
Joined: Jun 2004
Posts: 1,273
T
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I seriously doubt that the 'neutral bus' is fused -- it's a corner grounded delta -- hence the fusing to the 'neutral' it's a grounded 'hot.'

I absolutely HATE to sling around the term 'neutral' in such schemes. While a corner grounded delta certainly has been pulled over to ground potential, it absolutely has circulating current pumping in and out of it -- at a tempo far beyond the residual imbalances typical of a center tapped residential service.

[ Unlike a center tapped Service drop, one dares not ever break the bonding to the ground while power is applied. What's bad for a center tapped ground is horrific for a lifted corner on a delta. ]

[ EUSERC hates this old time scheme so much that you'd need a Presidential Executive Order to have a new one hooked up. Emergency responders will always mistake the grounded corner -- from the layout of the panel -- to be that of a single phase, center-tapped scheme. Not good. ]

Off hand, it smells like a distribution panel for site lighting.

Which is exactly the kind of system that would run on and on for years without an upgrade/ overhaul.

I'd expect that the service was some ancient 240 delta.

That far back 480 was just not done for such facilities.


Last edited by Tesla; 02/23/15 10:33 AM.
Joined: Jun 2004
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Since EUSERC hates corner grounded delta Services, I've never run across a single one.

I'd be interested to hear if a voltage tick reads 'hot' around such grounded legs of the power flow.

Let us know.


Tesla
Joined: Jul 2004
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I used to see corner delta on sewer lift pumps. As soon as I figured out what it was, I never saw anything unusual about it. It seems to have a certain elegance to it. A grounded conductor is a grounded conductor. It is simply an arbitrary decision at which point we ground the transformer secondary. I would be a lot more concerned with the center of a wye when you have reactive loads than a corner delta. It will only draw nominal circuit current. The main code/listing issue is that there is 240v to ground so the 2 pole breakers need to be "delta" rated.


Greg Fretwell
Joined: Jul 2004
Posts: 783
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Does it look to anyone else that many of the fuses have been replaced over the years? The labels on the fuses look too clean to be original. Why have they been replaced?

Joined: Jul 2004
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G
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They look like they are FRNs so they may have been instant blow before and someone decided a delay fuse was a better option.


Greg Fretwell
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