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Old 12-20-2011, 05:46 PM   #1
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Why did my breaker not trip? Need some assistance on this one.


My scenario, I'll try and describe as best as I can.

I have a stand alone workshop fed from the main located on the house going on 8 years now

I have a GE main panel feeding a small 4 breaker Gould sub panel located in my workshop with two separate 30 Amp Breakers using amp rated 10/3 solid copper One 30amp is feeding one side of the sub panel buss bar and the other 30amp feeding the other side. In between the circuit located inside the wall of my shop, I have a junction box where I have the wires separated then tied back together with wire nuts. red to red, black to black white to white and ground to ground. one day back October/11 while out in my shop, I saw a flash and heard a pop, I opened the sub panel up and noticed that the black wire where it ties into the buss at via crimp screw had melted through the insulation and welded to the panel, everything in the shop was still on and working but the 30 amp breaker feeding the black wire to the sub panel didn't trip, I opened both 30amp breakers at the main panel not knowing which one fed the black, later found which one was which, went back to the sub pulled the wire from the screw and inspected it put it back in then went and closed both 30amp breakers this time it arched through the insulation at the clamp where it goes into the sub panel again the 30amp breaker did not trip so I once again opened both breakers, pulled that section of wire from the sub panel to the junction box, completely out, when unscrewing the nuts, I did notice that I might not of had a good nutting on the black, inspected that section of wire cut the bad areas out and replaced it and made sure I had a good wire nut on the wires inside the junction box, so my question is why didn't the breaker trip when hot went to ground? So far everything is holding but I am still a bit concerned, Is the 30 amp breaker bad? Should I replace the 30amp breaker?

What occurrence that took place when this all happened, I had just turned on a small space heater inside the shop but the heater checks out good as I have it connected inside the house now. Could it of been a matter of time and the heater was enough to generate enough heat inside the wiring and the loose connection gave? I just don't know. So far everything is still holding after I replaced the wire and got tighter connections and have not yet replaced any breakers.
I worked in high voltage substations many years back and have a somewhat understanding of electricity but when it comes to residential things are a bit different, but I'm scratching my head on this one.

Thanks much
Randy

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Old 12-20-2011, 06:24 PM   #2
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Why did my breaker not trip? Need some assistance on this one.


At least two things must happen for a breaker to trip out !
The current must exceed a certain level ,
And it must do so for a certain time before it tripps out.

So why didnt yours trip out ?
It could be one or the other,
or a combination of the two.

The flash did not use 30a or more !
Or if it did so,
it was only for a breif period !
that was not long enough for a trip out.

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Old 12-20-2011, 06:28 PM   #3
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Why did my breaker not trip? Need some assistance on this one.


Sometimes the short will burn itself clear before the breaker trips. That appears to be what happened. The metal at the point of contact vaporized and opened the circuit faster than the circuit breaker. This doesn't necessarily mean the breaker is bad. However, your subpanel needs to be fed by a single double-pole breaker, not two separate single-pole breakers. You really should get a 30A 2-pole breaker and install that for your feeder.
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Old 12-20-2011, 07:14 PM   #4
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Why did my breaker not trip? Need some assistance on this one.


Ok so now I'm thinking that maybe I should drop those 30amp breakers to 20 amps?, Sub Panel has 4 20 amp breakers in it right now. Mpoulton by swapping out the two single poles to a single double pole would that make a difference other then added saftey by tripping out both sides? I'm also concerned about what caused the short (flash) it in the first place?

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Old 12-20-2011, 07:46 PM   #5
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Why did my breaker not trip? Need some assistance on this one.


How many wires are in the feeder to your workshop sub-panel ?? Include the ground if there is one.

You will either have 4 wires or 3 wires, which is it ? You said 10/3 which would most likely be 4 wires including ground.

How did you connect the ground of the feeder at your sub-panel ?? Same place as the white neutral or to a separate ground bar from the neutral bar?

Also you would have had a main bonding means ... a green screw or metal copper ground strap did you install that screw or strap?
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Old 12-20-2011, 08:00 PM   #6
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Why did my breaker not trip? Need some assistance on this one.


Next thing you need to do is replace those single breakers with a dbl. pole breaker. In the event of a short or overload, the whole panel must shut down, not just one leg.
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Old 12-20-2011, 08:01 PM   #7
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Why did my breaker not trip? Need some assistance on this one.


HI Stubbie

As mentioned in my original post 10/3 solid (not trying to be ugly) "red to red, black to black white to white and ground to ground" so 4 wires total Red, black, White and ground. This reminds me of when I went to pick up a 5' section of 10/3 at Homedepot they didn't carry solid on a spool so the guy says he has it in stranded, I said as long as I have two hots we are good so I get home only to find 10/3 stranded is not the same as solid it only has one hot, lucky it was their mistake and I got a refund.
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Old 12-20-2011, 08:06 PM   #8
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Why did my breaker not trip? Need some assistance on this one.


Quote:
Originally Posted by Missouri Bound View Post
Next thing you need to do is replace those single breakers with a dbl. pole breaker. In the event of a short or overload, the whole panel must shut down, not just one leg.

yes Missouri I'm going to replace those two single pole with a DBL Pole and reducing the 30 amps to 20 amps, that's what I'm thinking anyway. Noting I use in the shop is pulling over 20 amps, though I do have a DC (Dust Collection) 1HP motor that claims to be 20 amps and has yet to trip a 20 amp breaker that's with 14" BandSaw 1HP motor running at the same time.
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Old 12-20-2011, 08:08 PM   #9
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Why did my breaker not trip? Need some assistance on this one.


Can you rewire that DC to 240v?
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Old 12-20-2011, 08:10 PM   #10
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Why did my breaker not trip? Need some assistance on this one.


Yes it can be wired for 240, why do you ask?
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Old 12-20-2011, 08:20 PM   #11
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Why did my breaker not trip? Need some assistance on this one.


Just to balance the load a bit. Anything you can run on 240 would help that issue.
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Old 12-20-2011, 08:21 PM   #12
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Why did my breaker not trip? Need some assistance on this one.


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Originally Posted by Stubbie View Post
How many wires are in the feeder to your workshop sub-panel ?? Include the ground if there is one.

You will either have 4 wires or 3 wires, which is it ? You said 10/3 which would most likely be 4 wires including ground.

How did you connect the ground of the feeder at your sub-panel ?? Same place as the white neutral or to a separate ground bar from the neutral bar?

Also you would have had a main bonding means ... a green screw or metal copper ground strap did you install that screw or strap?
Both the ground and the neutral have separate bars.

Before the short inside the juntion box I had installed between the circuit I only had the grounds nutted together, After the short when I rewired them I twisted the grounds together real good with many wraps and no nuts this time as I didn't need it and grounded the metal juntion box as well via green screw.

If I understand your last question correctly? Both Panels already had separate bars, grounding and neutral.
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Old 12-20-2011, 08:23 PM   #13
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Why did my breaker not trip? Need some assistance on this one.


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Originally Posted by Missouri Bound View Post
Just to balance the load a bit. Anything you can run on 240 would help that issue.

I believe the bandsaw can be wired 240 as well but not sure if that's necessary?

Wait I misunderstood, 240 for 220, it can be wired for 220 as can the saw I think.

Well I stand corrected once again, I just checked my dryer receptacle and got 240 so 110/220 must be old standard now 220/240.

Last edited by Blackie_; 12-20-2011 at 08:39 PM.
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Old 12-20-2011, 08:40 PM   #14
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Why did my breaker not trip? Need some assistance on this one.


I would not downsize the breaker to 20 amps if you have #10 to the shed.
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Old 12-20-2011, 08:48 PM   #15
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Why did my breaker not trip? Need some assistance on this one.


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I would not downsize the breaker to 20 amps if you have #10 to the shed.

Jbfan

I thought that wire can be to small but not to big?

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