Intentionally creating branch circuit fault

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chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I know of guys that take a single pole switch and wire it between ungrounded conductor and grounded or grounding conductors to open and locate branch circuit breakers. What are the dangers to the electrical system from this practice?

Please keep the FPE/Zinsco comments out of this discussion.

Thanks
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
In theory there is no real hazard...in the real world the supply system is not perfect and you could have arcs and sparks where you don't want them. In the case of the grounding conductor, if it is not a complete path back to the main bonding jumper you would be energizing everything connected to that EGC.
 

LEO2854

Esteemed Member
Location
Ma
I know of guys that take a single pole switch and wire it between ungrounded conductor and grounded or grounding conductors to open and locate branch circuit breakers. What are the dangers to the electrical system from this practice?

Please keep the FPE/Zinsco comments out of this discussion.

Thanks
You could dump the whole building if the main is set too sensitive..:lol:
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I don't know why anyone would use that method. How do you know what will go out when you flip the switch? I agree with Leo also. I have worked in a building with the main set to light and the main tripped off when I accidently touched some 277 light wires together. And wouldn't you know it, it was right at 4:55, all the cashiers were trying to close out. No one was happy with me that day.

On a residential service, it would be just as easy to turn off the individual breakers and check voltage.
 

Cow

Senior Member
Location
Eastern Oregon
There was an article a few years ago about an electrician who caused a power outage at the federal reserve using the "switch" method to find a breaker. I think the link was posted here....

I can't think of a better excuse to own a circuit tracer.....
 

bobbymari

Senior Member
Location
los angeles ca
there are circuit locaters on the market. if this is residential just take the extra half hour to flip some breakers bro . helper and a walkie talkie works just as well this brought to you by No Shorts Electric:thumbsup:
 

templdl

Senior Member
Location
Wisconsin
This is a very tempting way to trip the branch breaker instead of taking the time to identify it and turning it off manually. On the surface it makes sense.
But three things come to mind:
1) Does the switch have a withstand rating? Closing a switch intentionally in to a bolted fault is not such a good idea. The intent of switches is to open and close lighting loads or items that are plugged into outlets if that is how it is applied not to close into a fault. Can the switch close into 10,000a? It should be a well known practice that you should never close even a breaker into a known fault. And someone does this with a light switch???
2) Remember there is no assurance as to how high that fault current will rise and every breaker that is in series with the fault will see it. If that fault current is high enough to fall within the instantaneous pickup of more than one of the devices it will be pot luck as to which one will trip, maybe the main?
3) I have always been of the belief that one should never intentionally rely of a breaker for over current or short circuit protection that is you should never intentionally tell yourself that I?ll just keep plugging things in to a circuit relying that the breaker will trip on overload nor I intentionally cause a bolted fault.
It?s the same with a GFCI. Even when protected by a GFCI I always treat electric tools as if there was not protection. Would you run the risk of working in a flooded area with and electric tool and rely of a GFCI to protect you from being electrocuted?
 

edward

Senior Member
Location
CA
Occupation
Electronologist
I have made myself a load bank with (4) small 1650watt hair dryers. Plug that puppy in and a 15Amp breaker trips in no time. I can only turn on (2) of the loads and do an amp measurement at the panel, verify which breaker it is then turn it OFF.

Besides the above test i can do other tests with it as well.
 

kwired

Electron manager
Location
NE Nebraska
I may be missing something, but isn't the first thing wrong, that you are wiring the switch hot?
Darn, someone got it before I did. I was thinking along the same lines when I read the first post. In order to comply with 70E wouldn't you need to turn the power off before wiring in the switch? If you still need to find the source after turning it off ....:eek:hmy:
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
After reading this, I have been trying to come up with a good analogy, how's this?

That's like testing the brakes on your car by driving 100mph towards a brick wall and hitting them at the exact calculated stopping distance. Technically, it should work but if anything goes wrong, not good.

I once had a boss who, when I asked him how I was supposed to make a test circuit for a GF trip on a 1000A main, told me to wire up a contactor to the load side of the breaker and short all 3 output leads to ground, then use a push button to energize the coil. I was fresh out of school and not real confident at standing up to the new boss, but that was stupid enough that I couldn't do it. I didn't get fired and the senior EE told him off about being an idiot, but the boss didn't like me for the rest of my time there.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
After reading this, I have been trying to come up with a good analogy, how's this?

That's like testing the brakes on your car by driving 100mph towards a brick wall and hitting them at the exact calculated stopping distance. Technically, it should work but if anything goes wrong, not good.

I once had a boss who, when I asked him how I was supposed to make a test circuit for a GF trip on a 1000A main, told me to wire up a contactor to the load side of the breaker and short all 3 output leads to ground, then use a push button to energize the coil. I was fresh out of school and not real confident at standing up to the new boss, but that was stupid enough that I couldn't do it. I didn't get fired and the senior EE told him off about being an idiot, but the boss didn't like me for the rest of my time there.
Not that I would have thought about it back when, but it doesn't quite sound like the way to check for a GF. Do we have pictures other than the one burned into your memory? Ground Bar or Earth?
 
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