TOPIC: Why have arc fault circuits

If this works there will be a picture of a outlet, a night light and whats left of a penny
One of my granddaughters slipped this penny behind the night light and the penny made contact with both prongs and the night light became a welder and cut the penny down to the size it is now
Tomorrow I will be installing arc fault breakers

Wow! That's incredible. I had to think about what happened for a second. So she dropped the penny from the top of the nighlight and it came down contact the prongs which created the arc, slicing the penny and the little bit fell through. Are there any pieces of the penny left or did it melt down and that's what I see attached to the prongs?

Definitely dangerous!

Wow! That's incredible. I had to think about what happened for a second. So she dropped the penny from the top of the nighlight and it came down contact the prongs which created the arc, slicing the penny and the little bit fell through. Are there any pieces of the penny left or did it melt down and that's what I see attached to the prongs?

Definitely dangerous!

You are correct, the penny melted and it is on the prongs.
The night light and the outlet still work

I wonder why the circuit breaker did not blow?
Will AFCI's address shorts, or just loose wiring/connections?
What type of panel is in the house? Would it be a Federal Pacific?

I wonder why the circuit breaker did not blow?
Will AFCI's address shorts, or just loose wiring/connections?
What type of panel is in the house? Would it be a Federal Pacific?

This is how a welder works, there is no dead short, the arc faults do protect from this situation, or when pets or children chew through extension cords,
This from a arc fault fact sheet

HOW THE AFCI WORKS
Conventional circuit breakers only respond to overloads and short circuits; so they do not
protect against arcing conditions that produce erratic current flow. An AFCI is selective
so that normal arcs do not cause it to trip.

"This is how a welder works,"
I agree.

"there is no dead short,"
I don't agree.

"the arc faults do protect from this situation, or when pets or children chew through extension cords,"

When a pet chews through an extension cord, the current passes through it's body.

When bringing a Hot or Neutral together, under controlled conditions, you can run a welding machine... the same spark that can light up steel can light up the inside of your walls.

Why do you think you need a larger breaker for a welding machine? If a breaker is not going to trip, why do you need a larger one? The breaker does what it does to protect the wires.

Like you said, it was "like a welding machine." You drew enough power to have a welding machine, but on a 15 or 20 amp fuse. How many amps does a welding machine draw?

I believe it should have blown

Try cutting a live extension cord. See if you blow a circuit.

AFCIs are new... until recently they were unreliable. The AFCI, protects againt arcing.

It you have a bad connection the electricty still wants to travel, and if possible will jump across the loose connection. (like a spark plug) This creates heat. This is what the AFCI is for.

AFCI's are a pretty new thing. It is just recently that they seem to have been perfected.

"HOW THE AFCI WORKS
Conventional circuit breakers only respond to overloads and short circuits;"

Yes, and a penny across a neutral and hot is a short.


"so they do not protect against arcing conditions that produce erratic current flow. "

That's right. Conventional circuit breakers do not protect against arcing, they protect against shorts.

"An AFCI is selective so that normal arcs do not cause it to trip."

Okay.