Wednesday, February 23, 2011

The wiring in your walls


We all have heard or scene at fires were the wire inside the wall gets blamed for the cause of the fire. The Usual cause it damage by a nail or staple coming into contact
With the wire were it goes thru a wood joist and some one hanging a picture or a carpenter putting up paneling or drywall gets blamed for causing the wire puncture.
But some times the lines are blurry when it comes to a piece of wire failing in a wall when it is between the wall studs hanging freely in the air
Can a wire fail for no apparent reason and can it be told it was before or after the fire it all depends who you talk to.
Many Electrical Engineers will tell you absolutely there is no positive way to tell pre or post damage to a wire like you might see on TV show like CSI
And claim that any engineer no matter what test he runs to prove it is no better at it than some one with an Ouija Board. (Pronounced We-ge)
While if you ask other professionals they will tell you positively that it can be established Pre or Post fire.
What it comes down to is science and whom the jury believes.
Recently while helping with an investigation of a fire I had just such a case were it appears that there was damage to a piece of wire in the air between studs. And it could possibly be from defective wire manufacturing and or rough handling of the wire.
But there is a problem how to prove it. One problem is was they a chair or other item along the wall were the wire supposedly failed. Could the chair have caught fire and then caught the wall on fire which would cause the wire to fail this scenario is very possible and is often over looked by investigators who would instantly say see it was electrical wire failure when in fact what was in front of the wall that caused the fire.
According to the homeowner there was nothing along the wall were this wire was located. And there was no charring or pattern on the floor to suggest any thing was in front of the wall. Next question was there any type of Electrical activity in the house. Yes home owner reports lights dimming and flashing occasionally and turning on and off and before they left for the day they smelled smoke in the room in question but attributed it to the belt on the vacuum cleaner they had run. In fact the homeowner was in process of getting an electrician to come over and check the wiring. Ok could a nail or other item have penetrated the wire and caused the problem. With as low as the wire was in the wall highly unlikely. Plus since the firefighter’s responding to the call turned off all of the breakers in the breaker box instead of just the main we have no way to know if the circuit in question tripped during the fire which could have been another clue.
So it does appear to be an electrical failure in the wire it self.
Now many engineers will argue how can a wire just fail in the middle you have a Romex wire were the ground, covered with paper the hot (Black) and neutral {white) are separated and white and black are both insulated how can there be any way for these wires to fail.
But lets look at some other factors what if the wire is defective from the factory right at this spot cases have been proven in court were defects in a roll of wire have occurred.
I recently had an Engineer show me pictures of a failure case involving defective MC type cable he had won. With all the miles of wire I have run in my lifetime it is rare but I have seen defects in a roll of wire and had to eliminate them. Especially in low voltage wiring.
Also (Romex) wire type NM is solid and solid wire tends to break easier than stranded.
At this point it will be up to the scientists and Engineers to argue out what happened but everything points to the wire failing. I will keep you informed as to what happens in the future.


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