Illegal to wire double 20A subpanel to meter?


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Old 10-03-10, 11:57 AM
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Illegal to wire double 20A subpanel to meter?

Guess what happend to me a couple days ago? I almost got fried. My screwdriver sure did! One laps in my thinking and BZHHHHHHHHHHHH! I was temporarily blinded, while the full available transformer amps sparked at a subpanel lug, like maybe you have never seen in your life!

My screwdriver turned into a molten glob at the end. And the shaft almost melted in half. After the episode, I tested across the 240 lugs, and to my dismay, I still had 240! Holy smokes.

So I went and traced to see where that old fashion flat cloth sheathed 6 ga. wire went to - and it went not into a main panel box in the next room, but directly to an empty round meter box outside!

This was in a duplex. So for the fun of it, I checked the other duplex. Same thing. This whole thing seems , if you ask me. I might have been seeing 60 - 200A sparks flying, for all I know.

Here I was real careful on the right lug, but on the left lug, my mind wandered somehow and I hit the outside of the 20A fused throwswitch box, with the shank of the screwdriver, while the tip was turning the left main lug screw. That is when the 4th of July occured. It looked like one of those fountain fireworks! For real.

And here is something else: There are (fresh looking)black arcing marks between a crossover metal electrical pipe, that joins the empty meter box, with the digital meter's box, to the metal siding. What made the current jump into the siding, rather than follow the path to ground? So I stared up at the wires overhead and saw no problem as to why the current leaped there the way it did. Maybe the ground wire inside was touching the metal pipe?
 
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Old 10-03-10, 12:56 PM
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The first question I would ask is why did you not lock out/tag out the power and check for voltage before doing work? Consider yourself lucky.
 
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Old 10-03-10, 01:01 PM
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I suggest the purchase of a non-contact voltage tester. They are about $10.

Can't say for sure why the current took that path to ground other then it must have been the path of least resistance.
 
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Old 10-04-10, 12:37 AM
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Ecman.,

I think it will be wise to call in a electrician to help you to investage the system due hevey short circuit and that is alot more than just 200 amp flowing thru espcally with bolted fault like your situation and you are D#mmed lucky on this one.

The bolted fault current can go more than just couple thousand amps { it can go up anywhere from 4 to 22K or more amps depending on set up }{ commercal is worst they can go 100K+ amp very easy.}

Most case it useally not a good sight to see a bolted fault do the damage to the stuff so a electrician able help you determed how much damage it got and with some of empty socket really somecase they are jumper on it due it was reconferaged to single meter { I have dealt alot like that and it kinda spooky if not carefull }


I noticed in your profile you live in EauClaire area and I used to live there for quite a while so I am famuair with the metro.

Anyway most 15Kw pig or box { pole or pad } the bolted fault current is typically about 6500 amp while 25Kw Pig can go pretty close to 8000 amps the larger one will varies a bit depending on type of transfomer and the way it serves the customer and service drop etc etc so the numbers may drop a bit.

{I have dealt with few bolted faults before so I know how it react with it }

Merci.
Marc
 
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Old 10-04-10, 05:00 PM
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Originally Posted by HotinOKC View Post
The first question I would ask is why did you not lock out/tag out the power and check for voltage before doing work? Consider yourself lucky.
I knew I had 240 volts. I simply wanted to make sure all electrical connections were tight since one of the two WH fuses blew for some reason. It was a 30 amp in there, which should not have blown. Someone put that 30 in there because obviously a 20 has blown before. The other fuse was a 20 and it did not blow. Nor was the 20A fuse lens discolored or bulged.

I ohms tested each element and each were the same. Neither showed a short to ground, either.

I have seen loose fuse sockets in these old fashioned fuse boxes get loose and cause heat, causing the fuse to blow. So that is what started me on the ride heading towards the fireworks.

With the fuse sockets both dead, with the throwswitch off, I tried to tighten each socket base. Then while I was at it I figured I'd check the main terminals. I knew they were live. I tightened the right one. Then when I tightened the hinged side one, I caught the door at the same time, because the door could only open about 70 degrees - and that screw was on that hinge side.

For the life of me, I do not know why I did not take more seriously the fact what would happen if I hit that door at the same time. Lucky for me. Unlucky for Mr. Screwdriver.
 
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Old 10-04-10, 05:06 PM
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Originally Posted by Tolyn Ironhand View Post
I suggest the purchase of a non-contact voltage tester. They are about $10.

Can't say for sure why the current took that path to ground other then it must have been the path of least resistance.
I have one - along with everything else you can imagine. I knew I had power. There was no issue there.

That is what I figured - the path of least resistance thing. But what was wrong with the main ground that this was the path of least resistance, I wonder.
 
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Old 10-05-10, 12:38 AM
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Originally Posted by Tolyn Ironhand View Post
Can't say for sure why the current took that path to ground other then it must have been the path of least resistance.
Electricity does NOT follow the path of least resistance to ground, it follows ALL paths back to the source. A path with a higher impedance will have less current (amperage) flow then will a path with lower impedance but when you are talking of a bolted short circuit the difference in amperage between a higher impedance and lower impedance short circuit is still going to be several hundred amperes.

Now whether or not the original installation was done in a code-approved manner (code as of the date of original installation) is a separate item. It could very well have been legitimate under the "tap" rules if the size and the lengths of the "unprotected" conductors (from the meter secondary to the switch) were not longer than the allowable length and of the proper size for the code cycle in effect at the time of installation.
 
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Old 10-05-10, 07:19 AM
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Originally Posted by french277V View Post
Ecman.,

I think it will be wise to call in a electrician to help you to investage the system due hevey short circuit and that is alot more than just 200 amp flowing thru espcally with bolted fault like your situation and you are D#mmed lucky on this one.

The bolted fault current can go more than just couple thousand amps { it can go up anywhere from 4 to 22K or more amps depending on set up }{ commercal is worst they can go 100K+ amp very easy.}

Most case it useally not a good sight to see a bolted fault do the damage to the stuff so a electrician able help you determed how much damage it got and with some of empty socket really somecase they are jumper on it due it was reconferaged to single meter { I have dealt alot like that and it kinda spooky if not carefull }


I noticed in your profile you live in EauClaire area and I used to live there for quite a while so I am famuair with the metro.

Anyway most 15Kw pig or box { pole or pad } the bolted fault current is typically about 6500 amp while 25Kw Pig can go pretty close to 8000 amps the larger one will varies a bit depending on type of transfomer and the way it serves the customer and service drop etc etc so the numbers may drop a bit.

{I have dealt with few bolted faults before so I know how it react with it }

Merci.
Marc
Marc, Eau Claire must be famous. I think Mitch, a mod here at DIY, lives here or in the area, and others like Concretemasonry are familiar with it. Nice clean town and it nice here right now. Beautiful fall weather. Excellent roofing weather.

Anyway, wouldn't such high amps that flew threw this line, have caused the #6 wire to melt in half?

Yes, I was lucky - and do not know for the life of me why I stopped thinking, when I told myself to be carefull on the right lug, but then my brainstopped working on the left lug. Strange.
 
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Old 10-05-10, 07:23 AM
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furd,

Does that make "the path of least resistance" expression a fallacy or wives tale? If so, how did that one start?

What you are saying is that if there is a grounding fork in the road, it will go down both roads in some sort of proportion to their impedence?
 
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Old 10-05-10, 08:59 AM
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Originally Posted by ecman51` View Post
Does that make "the path of least resistance" expression a fallacy or wives tale? If so, how did that one start?
I'd say it's an oversimplification. The majority of the current does take the path of least resistance, but that's not the only path it follows.

What you are saying is that if there is a grounding fork in the road, it will go down both roads in some sort of proportion to their impedence?
Correct, even if it's a 4-way or 10-way fork.
 
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Old 10-05-10, 03:42 PM
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Originally Posted by furd View Post
Electricity does NOT follow the path of least resistance to ground, it follows ALL paths back to the source. A path with a higher impedance will have less current (amperage) flow then will a path with lower impedance but when you are talking of a bolted short circuit the difference in amperage between a higher impedance and lower impedance short circuit is still going to be several hundred amperes.
That is a great point. I never thought of it that way but it makes perfect sence!
 
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Old 10-05-10, 06:32 PM
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Furd have good explaination with this situation.

I know any fault it will find anyway of means.

By the way ECman the Eau Claire mean Clear Water in French.

Merci.
Marc
 
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Old 10-06-10, 07:06 PM
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Originally Posted by french277V View Post
By the way ECman the Eau Claire mean Clear Water in French.

Merci.
Marc
Achtung! This German knows.
 
 

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