# Tight staples



## Switched (Dec 23, 2012)

I have seen fires, that burnt a house down, from staples that damaged the nm cables.

It may take years to happen though.


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## backstay (Feb 3, 2011)

Switched said:


> I have seen fires, that burnt a house down, from staples that damaged the nm cables.
> 
> It may take years to happen though.


Really, you seen this. I've heard it once, but like all unknown fires"it was electrical".


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## Toto (Jul 27, 2011)

Yes, but the staples did not penetrate the insulation. They only dented it. They actually dented the white and black insulation too, but never created a short. Would the deformity create this much heat build up? Oh, and the melted romex was between staples and not touching one.


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## Toto (Jul 27, 2011)

I've seen tight staples create shorts. Usually trips a breaker immediately.


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## Deep Cover (Dec 8, 2012)

Tight staples will not cause a fault or cause insulation to melt between staples. There is something else going on.


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## Switched (Dec 23, 2012)

backstay said:


> Really, you seen this. I've heard it once, but like all unknown fires"it was electrical".


Yes, only once. I was there at the same time as the fire inspector. He knew it was an electrical fire, and asked for my help. We were able to locate the fault to a tightly stapled nm wire. It fed a bathroom exhaust fan. 

The home was built in the 60's, ungrounded 2-wire circuits. It had a SQD QO panel and breakers, nothing ever tripped. With the exception of the panel, no electrical work had been performed since the original construction. The home caught fire in the early 2000's, so were talking 40 plus years for it to happen.


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## Switched (Dec 23, 2012)

This was clearly not just a tight staple. It severely damaged the conductors.


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## Spark Master (Jul 3, 2012)

I watched a house burn down from an engine fire of a car in the garage.

The fire marshal said it was electrical from the garage door opener. They write anything they want to close the case and walk away.


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## Toto (Jul 27, 2011)

Actually it looks like every staple in the house is way too tight. Never seen that before. They had another electrician out for same problem before. He just replaced burnt wire and called it good. But I have to have a cause before I can leave it. I replaced all wire under house. Could be a tight staple in wall shorting out periodically or a short in the fixtures. I've always heard Zinscos don't work. Here is obvious proof. Thanks for input.


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## Deep Cover (Dec 8, 2012)

Were they metal or plastic staples?


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## Toto (Jul 27, 2011)

Metal


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## HARRY304E (Sep 15, 2010)

Toto said:


> Metal


Some people go way overboard with the 32oz hammer./...:laughing:


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## Deep Cover (Dec 8, 2012)

But then the cable would fail at the staple. I can't understand the use of metal staples on NM and I still think you have something else going on...my first thought was space heater or an animal chewing combined with Zinsco breakers.


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## Toto (Jul 27, 2011)

Yep. Doubt animals unless they're only in the walls--no signs of them anywhere else. But maybe a tight staple in the wall or a short at one of the fixtures. I'm inspecting them next. I just hate not being able to find the cause. I don't want to tear the walls apart and come up empty. I guess I should replace all the romex that's been exposed to that much heat anyway, though.


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## chicken steve (Mar 22, 2011)

wood _'breathes' _with the seasons , especially true for those cellars that assume some dampness in spring, then dry out toward fall

the phenomenon can also be witnessed in fasteners one uses to construct say, a barn , out of recently (not kiln dried) lumber 

that continuos cycle tends to displace fasteners, some having a sucked in appearance 

~CS~


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## wcord (Jan 23, 2011)

Switched said:


> I have seen fires, that burnt a house down, from staples that damaged the nm cables.
> 
> It may take years to happen though.


Same here. Didn't help that the homeowner had increased the breaker size because the 15 kept tripping. I was there checking out why the circuit was out and caught the fire just after it started. 20 minutes later and the house would have burned to the ground.


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## nolabama (Oct 3, 2007)

switched said:


> i have seen fires, that burnt a house down, from staples that damaged the nm cables.
> 
> It may take years to happen though.


x2 ''


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## chicken steve (Mar 22, 2011)

wcord said:


> Same here. Didn't help that the homeowner had increased the breaker size because the 15 kept tripping. I was there checking out why the circuit was out and caught the fire just after it started. 20 minutes later and the house would have burned to the ground.


Methinks you saved our trade one notch on the electrical bad rap meter WC:thumbsup:

~CS~


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## Big John (May 23, 2010)

I've seen tight staples trip ground-fault interrupters, but if your insulation is intact you won't have enough current flow to generate that much heat. 

So either you have an actual short at the staples or there's another cause. This is the type of thing meggers were invented for.


Switched said:


> Yes, only once. I was there at the same time as the fire inspector. He knew it was an electrical fire, and asked for my help. We were able to locate the fault to a tightly stapled nm wire....


 So he'd made up his mind it was an electrical fire and only needed to find the cause? :lol:


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## backstay (Feb 3, 2011)

So the staple is causing a increase in resistance of the wire? I call BS. You would have to smash the conductors, flatting them a lot to get this to happen. Sounds like a overloaded circuit, period.


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## Toto (Jul 27, 2011)

circuit is not overloaded. It only uses 3 or 4 amps when the lights are on. But my hunch is that the staples smashing the wires is just coincidental with the heated wire. Two possibilities then:
1)An intermittent short that has not been fixed and may show up again--this leaves the house in serious danger.
2)A past issue that has been resolved or removed and no one remembers or noticed.

I won't gamble a house on #2


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## HARRY304E (Sep 15, 2010)

Toto said:


> Yep. Doubt animals unless they're only in the walls--no signs of them anywhere else. But maybe a tight staple in the wall or a short at one of the fixtures. I'm inspecting them next. I just hate not being able to find the cause. I don't want to tear the walls apart and come up empty. I guess I should replace all the romex that's been exposed to that much heat anyway, though.


I would not spend too much time on it when you get to the point where you've got to open walls!,Then it's time to pull in a new circuit.


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## Mshea (Jan 17, 2011)

Switched said:


> This was clearly not just a tight staple. It severely damaged the conductors.


 My first fire investigation the cause was due to too tight a staple. NM cables must be able to move under the staple.
By driving the staple too tight the insulation gets crushed or at least very squeezed. It's dielectric stenght is reduced and often low enough that the 120 volts can break down the insulation. This can result as a carbon trace from hot to ground or neutral and eventually the carbon trace gets to be a carbon track then an high resistance short circuit often with lees than 5 amps flowing from the hot to the return path. eventually the carbon tracks light the wood the stapels are driven into and we get the invitaion from the Fire Department to figure out the cause.

So you are wondering how we extablish it was the staple and not a fault in the wire. We found carbon arcing evidence at several other staples in the area of the fire. The fire left a lot of evidence behind as it was put out fairly early. Insuarance company paid for a complete rewire as we condemed the installed wiring. I think it took over 30 years to start the fire.
Too tight of a staple can start a fire and I am not the only person to make this observation as I have read other fire reports that attributed the cause to damage to the wire from stapling.


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## Auselect (Dec 2, 2011)

Mshea said:


> My first fire investigation the cause was due to too tight a staple. NM cables must be able to move under the staple.
> By driving the staple too tight the insulation gets crushed or at least very squeezed. It's dielectric stenght is reduced and often low enough that the 120 volts can break down the insulation. This can result as a carbon trace from hot to ground or neutral and eventually the carbon trace gets to be a carbon track then an high resistance short circuit often with lees than 5 amps flowing from the hot to the return path. eventually the carbon tracks light the wood the stapels are driven into and we get the invitaion from the Fire Department to figure out the cause.
> 
> So you are wondering how we extablish it was the staple and not a fault in the wire. We found carbon arcing evidence at several other staples in the area of the fire. The fire left a lot of evidence behind as it was put out fairly early. Insuarance company paid for a complete rewire as we condemed the installed wiring. I think it took over 30 years to start the fire.
> Too tight of a staple can start a fire and I am not the only person to make this observation as I have read other fire reports that attributed the cause to damage to the wire from stapling.


So why are metal staples allowed by code? Of all the billions of staples that have been installed just last year, I'm sure many were hammered too far....what, not enough fires to ban metal staples or is it really not a concern? Because the NEC is purely to prevent fires you think that might of been high on their list if it was a problem???

I personally hate metal staples, Im used to using the plastic "c" shaped strap with 1 nail attached, they hold to the wire so you don't need to hammer through my fat fingers holding the staple, leaves your hand free to hold the wire neatly....I just haven't found reasonably priced ones here yet....


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## Toto (Jul 27, 2011)

Mshea: How tight were the staples you saw that started fires? This whole house (wired in the 70's or so) has over hammered staples. Copper is actually slightly deformed in a lot of the romex. I think the only reason the romex wasn't punctured is because the staples have that wide surface on the cross section that is designed to distribute the force out.
I hardly ever see over tight staples in the field. I think almost every electrician has a natural fear of pushing a metal conductor down across the hot and the neutral.
Thanks for the info guys.


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## Spark Master (Jul 3, 2012)

When I redid my house, every staple was smashed into the cloth romex. (1950 build date) 
Nothing was burnt, and I physically removed every inch of original wire from my house.

I would say you really need to breach the sheathing and insulation to have a small amount of current flowing.


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## macmikeman (Jan 23, 2007)

This conversation should not even be going on. Since arc fault breakers are now mandatory in just about everywhere in the house, and the authorities love them so so so very much, you should be able to drive ten nails thru each cable run just for the love of it and pass an inspection. Cause we all know the arc fault breaker will take care of everything, and certainly it will prevent any more fires...


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## Switched (Dec 23, 2012)

Spark Master said:


> When I redid my house, every staple was smashed into the cloth romex. (1950 build date)
> Nothing was burnt, and I physically removed every inch of original wire from my house.
> 
> I would say you really need to breach the sheathing and insulation to have a small amount of current flowing.


Yeah, you have to smash the crap out of it. But remember, the staples we have now, they are much different. A lot of the older staples were very thick, without a tapered or rounded edge. They are not the same product we use today.

These type of things are an exception, not the rule. Just because you have never seen it, doesn't mean it doesn't happen.


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## chicken steve (Mar 22, 2011)

Mshea said:


> By driving the staple too tight the insulation gets crushed or at least very squeezed. It's dielectric stenght is reduced and often low enough that the 120 volts can break down the insulation. This can result as a carbon trace from hot to ground or neutral and eventually the carbon trace gets to be a carbon track then an high resistance short circuit often with lees than 5 amps flowing from the hot to the return path. eventually the carbon tracks light the wood the stapels are driven into and we get the invitaion from the Fire Department to figure out the cause.
> 
> So you are wondering how we extablish it was the staple and not a fault in the wire. We found carbon arcing evidence at several other staples in the area of the fire. The fire left a lot of evidence behind as it was put out fairly early. Insuarance company paid for a complete rewire as we condemed the installed wiring. I think it took over 30 years to start the fire.
> Too tight of a staple can start a fire and I am not the only person to make this observation as I have read other fire reports that attributed the cause to damage to the wire from stapling.



I have rewried many an older install where removing the embeded staple revealed insulation damage

but rarely have read an explanation as eloquent as this

Do any periodicals or editorials out there exist on this phenomenon Mshea?

~CS~


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