General question about arc flashes

hoof print · Nov 18, 2021

I was on YouTube and ended up watching some arc flash videos. Those videos will certainly get your attention and make you think about how you reset a tripped breaker.

How common are arc flashes in a household setting with typical 200 amp service? I have a healthy respect for electricity, but never considered an arc flash happening at my home panel.

phil25 · Nov 18, 2021

Can it happen in a household panel??? sure anything is possible, given the possible following details, age of panel, number of overload circuits, environment around panel, moisture, dust,
workmanship when the panel was installed, quality control of panel company, quality of new or used breakers, owners knowledge in general doing connections/changes, rodent,etc etc as others may add. In short I assume that the potential is there, respect that potential, reduce the potential,
potentially you will never experience it.
hope I answered your question somewhat.

1948CaseVAI · Nov 18, 2021

Most things are possible. The question is whether or not it is common and likely. Since you rarely hear about it I presume it is uncommon and therefore unlikely.

Philip d · Nov 18, 2021

We had a few cases we had to use used 60&100a federal pioneer breakers to get people going as new ones werent available. A couple of those times you could hear them sizzle ,luckily they didnt cause an arc flash before we turned them back off.

dr sportster · Nov 18, 2021

If you watched the one where the guy is racking a big breaker back in a high voltage panel and it explodes Then someone says the guy was not hurt .When I watched the same movie at the power company they said it was a fatality. Always turn your head and reset with left hand pinky. Don't worry to much about this.

johndeere720GA · Nov 18, 2021

I would not be too quick to sacrifice the pinky finger (5th finger). You may be surprised to know that that humble little digit supplies (differing opinions) 20 to 50 percent of your grip strength?

Tony in SD · Nov 18, 2021

It has been a long time since I attended a continuing education seminar that talked about arc flashes among other topics. If my memory serves me correctly, arc flash is not much of a concern under 240 volts served by a transformer under 125 kva. Arc flash is dependent on the amount of current supplied by the utility company. Most household are feed by transformers well below 125 kva.

Phil-mar Farms · Nov 18, 2021

X2. The pinky finger on my left hand is numb because of a severe cut. I miss the function of it

Steve@Advance · Nov 18, 2021

Few years ago I ran a 200A service for our big lather here at the shop.

Bought a used Square D breaker, even used it was not cheap! It looked great, used but not abused.

I went to stab it in, as soon as it touched something hissed, sounded like striking an old kitchen match, and a tiny whiff of smoke came out the front.

My first inclination was to drop it and run, but didn't want it to hit the floor, and decided I couldn't outrun it anyway, so I just shoved it on in.

And that was the end of it, nothing blew up, the breaker worked fine, it's still in there doing it's job.

I did turn it on with a stick the first time though!

37 chief · Nov 18, 2021

At first I thought you were talking about arc welding. I have had a lot of flashes from welding.I had a arc flash one time. I went to another plant to unhook some machines to move to our plant. I didn't have a meter to check for voltage. The other maintenance dept. said all power was shutoff. I carefully unwrapped on leg of 3ph 440v, and grounded it to make sure it was off. Well it wasn't. I did see an arc flash, and ruined a good screw driver. I should have requested a meter, but I was in a hurry to get back. Stan

David Snipes · Nov 18, 2021

I know a guy who was arc flashed by 50,000 volts. He looked like a barbecued lobster but he survived and spent much time in a burn center.

Dennis Minn · Nov 18, 2021

hoof print,

I spent many hours collecting data for teams of folks to properly calculate arc flash incident energy.

I promise to get back to you. Your life is dependent on proper evaluation and protection, be it ppe gear or a complete de-energization.

We have some generic placards for 240vac household services. There is a lot of assumptions in the calculations, and they favor worst case.

D,

farmallboy15 · Nov 18, 2021

From the training I had, arc flash is nearly non-existent in single phase panels (like most homes). You can get electrocuted or shocked by your homes panel, but typically it takes 3 phase to get the arc flash /explosion going. Risk for arc flash goes up the older and dirtier the panel gets. Metal dust in the air, exponentially higher.

Janicholson · Nov 18, 2021

Real approved safety glasses are UV blocking. Arc flash can toast your exposed skin, and worse if longer than milliseconds. People have had their soft contact lenses welded to their cornea! Real protection is lockout tag out and metering where exposed contacts are seen. I fight the wear your safety glasses on your eyes battle every day because 19 to 30 year old humans are indestructible (right) Jim

Philip d · Nov 18, 2021

Haha I can imagine,I wonder if some of them just have enough moisture in them to act up at first and if they hold will dry out and be fine once they warm up under load?

4520BW · Nov 18, 2021

Your correct! I have to take a class on arc flash every 3 year. We finally got fast blow fuses installed at work that cut down on wearing the big heavy suite.

RJKeith · Nov 18, 2021

Generally arc flash is not a problem in residential services. Utility companies typically use a 10KVA transformer, which limits the amount of energy available. In addition, your service feeder is probably 4/0 or less aluminum and 50 to 150 feet long, which further knocks down the energy. Arc flash is more of a problem for large services (2000 amps or more), 480 volt services, and especially medium voltage equipment. The typical rural house just doesn't have enough energy available for significant danger.

M-MAN · Nov 19, 2021

I remember when all the new regs were supposed to go into effect. Our safety coordinator brought in these high dollar consultants and we had training after training. The plant got rid of all our meters except for the electricians. Said we were no longer allowed to open any of the hv panel boxes. Problem was there was only one electrician for each plant and they worked first shift. Every machine had two hv panels and we had to open up a few every shift. Had to buy our own meters then just so we could do our job.

They never did buy a suit for the electrician.

Determined · Nov 19, 2021

(quoted from post at 11:30:32 11/18/21) I would not be too quick to sacrifice the pinky finger (5th finger). You may be surprised to know that that humble little digit supplies (differing opinions) 20 to 50 percent of your grip strength?

I lost a pinky in July, the surgeon who patched me up managed to save about 1/4 inch of the bone forward of the bottom joint.

He said it would help considerably with grip strength once the hand has healed.

That little nub can't actually touch or hold anything but overall it does seem to add to holding power.

When you pick up something round for example and the other finger tips are touching it your mind is saying it wants to feel the pinky touching it as well, this almost involuntarily causes the grip of the lower part of the hand to tighten.

KMCL0610 · Jan 28, 2022

While experiencing a 20A or even 60A wire come free when lifting a dead-front could be ""exciting,"" it's nothing compared to having anything fall on the main supply.

Taking the dead front off a 240V-200A board isn't the same as operating on high-voltage switchgear, where arcs may be large, objects that may not transmit do, and opening or shutting a button are momentous occurrences. However, seeing a homeowner's mains break free when you're 12"" distant from the board in a closet makes me reconsider my position on Arc Flash safety

General question about arc flashes

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