Meltdown

[pridelion]

A buddy of mine tells me the following story.....that he knew of an electrician that went on a call of loss of power to a house. When he arrived,themain breaker was tripped. He reached over without any further checking, flipped the main back on and poof! It bursts into flames and begins to burn up the s.e. feeders as well. Does this sound plausible? What would cause this? How could I avoid the same type of blunder?
Thanks! John

 

[bphgravity]

Re: Meltdown

A malfunctioning breaker that results in a fault line to line can certainly be explosive, especially if the AIC rating is exceeded. Or perhaps the fault is downstream on the bus or feeder circuits, same result.

You already know the answer to your last question. Don't go throwing main breakers closed without first correcting why it tripped in the first place.

 

[George Stolz]

Re: Meltdown

Originally posted by bphgravity:
Don't go throwing main breakers closed without first correcting why it tripped in the first place.

What would you do? Ohm it out on the load side of the breaker? If it zeroed, I would keep hunting. Otherwise, I would probably turn it on to throw a clamp on it. The same thing would have happened to me.

 

[bphgravity]

Re: Meltdown

I'm not saying that this can't happen even if all precautions are made to prevent it. A bad breaker is a bad breaker. However, the original poster indicates the electrician did nothing before trying to reset the main.

1. Did he first open all breakers and downstream loads?

2. Did he first make a visual inspection of the bus and components iside the panelboard?

3. Did he first ohm out circuits to identfy ground-faults or short-circuits?

All I'm syaing is that IF the fault is with other than with the main itself, that fault may have been identifiable and corrected before just simply trying to reenergize the system.

 

[pierre]

Re: Meltdown

I agree with Bryan. I will add that there is very little if any training that teaches an electrician the proper way to handle this type of situation. How many times has a circuit breaker tripped and someone just tries to reset it? Probably BILLIONS OF TIMES!!!!!

There can be many reasons of which most probably are not life/equipment threatening. But there have also been many times (not quite billions ) that life and equipment has been affected by just resetting a breaker.

We are always in such a hurry, that sometimes we do not stop to think. But the proper procedure could be a way to add to the bottom line for your business as well as keeping you and the equipment safe.

 

[charlie tuna]

Re: Meltdown

i was once called to a residence where the homeowner upgraded his own service from one hundred amps to two hundred amps. a freind helped him out that had some electrrical knowledge!

the only thing the homeowner needed to do to complete the job was install the panel cover. his electrical friend was gone. the last cover screw went into the panel and into a phase conductor and it was on the line side of the service ahead of the main. it caused the service wires to melt together -- that started a phase to phase fault -- directly from the power company's transformer. it finally blew the primary fuse after melting his overhead service drop half way back to the pole!!!

 

[augie47]

Re: Meltdown

EVERY electrician should see one of the SHORT CIRCUIT/FAULT CURRENT films put out by Bussmann and other OEM's.
IMHO, it places a lasting memory in your mind thats makes you a bit more cautious.

Last week I was using the phone at a supply house when a plant electrician came by to pick up a half-dozen 200 amp fuses (Class K5) because "they keep blowing", and a box or two of 30 amp renewable link fuses.

I'm attempting to convince management of this facility to hold a class in fault current.

[ September 12, 2005, 09:30 AM: Message edited by: augie47 ]

 

[charlie tuna]

Re: Meltdown

i have a copy of the bussmann film and loan it out to building engineering departments to show their crews. it is a very good film!!! i ordered it through my local supplyhouse ---no charge.

 

[catchtwentytwo]

Re: Meltdown

Pierre's post in the "duplicate" is worth mentioning. WWW.bussmann.com

This website has an incredible amount of FREE information that will help any electrician. One of the items there is about Arc Faults and Arc Blasts. You should visit this site and spend some time there with this info, as it will only make you better at what you do.

--------------------
Pierre Belarge
Inspector, Instructor &
Industry Advocate

 

[pierre]

Re: Meltdown

"i was once called to a residence where the homeowner upgraded his own service from one hundred amps to two hundred amps. a freind helped him out that had some electrrical knowledge!"


WARNING...WARNING WILL... DANGER, DANGER!!!!

That is what I usually say to people who tell me their friend knows electrical.

Does anyone remember what TV show that is from?

 

[petersonra]

Re: Meltdown

a little knowledge is a dangerous thing.

most people are knowledgeable enough about electricity not to touch a bare wire. but, there are electricians who think it is a good idea to test for a hot wire with a damp finger.

 

[ed downey]

Re: Meltdown

"Lost In Space"

Danger Will Robinson Danger!

 

[26member]

Re: Meltdown

yes ,just enough knowledge to burn the house down and not enough to prevent loss of life

 

[don_resqcapt19]

Re: Meltdown

1910.334(b)(2), Reclosing circuits after protective device operation. After a circuit is de-energized by a circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized.

 

[petersonra]

Re: Meltdown

how many HO's have ever read osha rules?

the bottom line is that if a CB trips in a house, the vast majority of the time the HO will reset it.

the vast majority of time in an industrial setting if a CB trips, the elctrician will come out and reset it. I have NEVER run across a case where I have seen an electrician do anything other then reset the CB in such a case.

to me, it makes sense to do some checking if it is a main breaker, or maybe a bigger circuit, but typical 120V circuits do not present a serious hazard merely by resetting them.

 

[charlie b]

Re: Meltdown

I recall from my Navy days that it is acceptable to attempt to close a breaker one time, after it has tripped. If it trips a second time, then you must tag it out and find the problem. I do not recall having to do any troubleshooting before that first attempt to reclose.

Perhaps there are some ex-Navy members of this Forum who were in active service more recently than I, and who can confirm or refute that this is the current Navy practice. Things may have changed since the days of my service with Admiral Lord Nelson at the Battle of the Nile.

 

[Leitmotif]

Re: Meltdown

I recall from my Navy days that it is acceptable to attempt to close a breaker one time, after it has tripped. If it trips a second time, then you must tag it out and find the problem. I do not recall having to do any troubleshooting before that first attempt to reclose.

Perhaps there are some ex-Navy members of this Forum who were in active service more recently than I, and who can confirm or refute that this is the current Navy practice. Things may have changed since the days of my service with Admiral Lord Nelson at the Battle of the Nile.

Charlie
Amazing how that training the Navy beat into our heads sticks. I remember that also.

You have senorioty on me I am just a young pup from the Nimitz days.

I also remember ABC 123 Black White Red for phasing. Wish I did not it screws me up when I do Black Red Blue - or is it Black Blue Red - that dang white.

 

[charlie b]

Re: Meltdown

OK. I really wasn't in the Battle of the Nile. But I did serve on the Nimitz (1976-79).

Of course, now that you have reminded of the "ABC 123 Black White Red" pattern, I'll probably never get it right again.

 

[Leitmotif]

Re: Meltdown

OK. I really wasn't in the Battle of the Nile. But I did serve on the Nimitz (1976-79).

Of course, now that you have reminded of the "ABC 123 Black White Red" pattern, I'll probably never get it right again.

Charlie

Well I did not serve with Nimitz either. I was on a Thresher class sub Barb SSN 596 from 69 - 73.

I guess I have now caused confusion with you on Black White Red. There is an upside and a downside.
UPSIDE I don't feel so stupid anymore.
DOWNSIDE I made life more difficult for you. Sorry about that

 

[WesWalker]

You are quoting the robot from Lost in Space

"Danger! Danger, Will Robinson! Dr. Smith is approaching."