OT: Electrical Fire

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I went to turn the pool pump on today and noticed the outlet the timer plugged in to was charred and black. I'm not 100% sure of the cause, but the important thing is the electrical box contained the fire and prevented it from spreading.
I'm not sure of the exact cause (I suspect it was a combination of things), but the outlet shows the most char (the fire happened in the box) while the pump power cord was melted to the timer.
I suppose I'll have to have an electrician come out on Monday. Anything I should ask them before accepting them?
Puckdropper
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Never teach your apprentice everything you know.

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My suspect is a loose wire (due to heat of the day or vibration) and arcing did the rest.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net "Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
On 7/3/2010 8:44 PM, Puckdropper wrote:

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I took the timer apart, and think I've found a contributer. The timer outlet connected via 6" long wires with 16 gauge wire. The hot wire shows a significant amount of melting (plastic completely removed) while the nuetral and ground wires are fine.
Once I get some daylight, I'll take the outlet apart and look around there.
Puckdropper
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"Puckdropper" <puckdropper(at)yahoo(dot)com> wrote in message

Any lightning in the area? Not a direct hit, mind you, but a jolt to the ground that found its way to the pool circuit.
I had a similar situation a couple of weeks ago. I'm not sure where the hit was, but an X-1- module in the garage was burned, as was the receptacle it was plugged into. Repaired that and found that the outside light fixture it control was out. One bulb had the base welded into the socket so I replaced the fixture. Doing so, If found a 3/16" hole in the downspout where there was an arc from the lamp holder that was nearly touching it. Travelled back to the main panel where it took out a breaker, AV receiver, and TV on that circuit.
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No lightning anywhere around for the last several days. Not even a drop of rain (pardon my use of that 4-letter word).
Puckdropper
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"Puckdropper" wrote:

------------------------ Classic description of an arcing ground fault.
The fault current was less than the rating of the protective device which allowed it to continue until it reached open circuit which was probably a conductor that melted thru.
Consider yourself lucky.
During my career, had a customer who lost a 1,200 amp, 480V switchboard the same way when a rat touched a hot bus bar and case ground at the same time, on a cold winter's evening.
The plant was down almost a month while a replacement switchboard was built, then installed and fire repairs were made.
Lew
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That does make sense. I could see a partial short arcing and snapping for quite some time until something burns.
Isn't the GFCI supposed to detect and trip when this occurs? The outlet was an older GFCI (at least 3 years old, it was here when we moved in) and might have failed on. OTOH, if the arcing was occuring before the outlet it would have done no good to trip.

I do, but want to point out that the outlet box was responsible for stopping the spread of fire.
We've got space to mount the electrical box on its own post 6-18" away from the deck, so if something happens again a fire would have to travel that far to catch the deck. *snip*

Puckdropper
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"Puckdropper" wrote:

You have answered your own question.
One of the advantages of having a GFCI c'bkr as opposed to a GFCI receptacle.
Lew
Lew
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On 04 Jul 2010 07:53:23 GMT, Puckdropper <puckdropper(at)yahoo(dot)com> wrote:

A GFCI only trips on a fault to ground. This may have been a high resistance or intermittent connection, like a loose screw, which an AFCI would catch but a GFCI would not.

That's why they're required. ;-)

If it makes you feel better. An electrical fire isn't likely to get out of a weatherproof box before the breaker trips.
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Not always the case , I have a GFCI in my bathroom, it covers my 2 boathrooms, out door outlets, kitchen, and garage outlets. It is not unusual for that thing to trip under a load form a power tool.
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Your tool has a leak to ground.
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Apparently all of them do, and it only happens on hot days when I have the radio, fan, dust collector, air compressor and what ever tool pushes the 15 amp circuit past it's limit on at the same time. Typically it only happens when the compressor decides to cycle with all this other stuff running. Have fewer of them on in any combination and it does not happen at all. It use to be that cutting a thick board on my smaller TS would do the trick. So it is certainly a load thing.
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On 7/5/2010 9:31 AM, Leon wrote:

Is it the GFCI or the breaker that is tripping?
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On 7/5/2010 8:31 AM, Leon wrote:

There's a good chance that if it's done that as much as this one has it is no longer providing ground fault protection at all.
When you replace it look for one with "smartlock" which won't allow a reset if the receptacle is not functioning as designed. Hospital grade all have that now, IIRC ... spendy, but worth the price for those areas where you really need gfci protection.
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It happens probably once each summer if I am not careful with the loads and if the day is HOT enough. More heat, more fans running. ;~)
The test button still makes it trip instantly.
I'll look into the smartlock one if I have any pressing problems.
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wrote:

with a leading or lagging current the device can detect the difference between legs.
Mike M
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I believe the compressor coming on indeed is when the GFCI trips. Typically I try to turn the compressor off if I am going to be running much at the same time.
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Sorry but a GFCI breaker only detects differences between current in the hot and neutral.
Phase angle and waveform distortion cannot and donnot cause a GFI or GFCI breaker to detect faults to ground. What is detected in one leg is the same detection circuit in the other leg of the wiring because it is the same sensing mechanism.
Inductive (motors and coil) loads starting or stopping can give high voltage kicks (high voltage spikes) and one side is tied to ground via the street transformer and other loads to neutral in different locations / circuits in your house. The other line (neutral usually) of the device acting up gets a high voltage spike that can punch through insulation weak spots and trip the GFI detection circuit. Drywaller's routers nick the insulation on wiring inside metal boxes and dust (where would that be in a woodshop?) combined with moisture (humid weather lately?) bring out the best in our wiring integrity.

.
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That's still leakage but if so, replace the GFCI. Older ones had this issue but it's been fixed with more recent units.
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If that's the case it's not the GFCI tripping, rather the OC device tripping (may be the same).

Sounds like an over-current trip.

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