Energized Neutral Problem

[txaggie84]

I investigated a house fire yesterday that appears to have originated in the breaker panel. When the occupants went outside after being awakened by their smoke alarm they noticed sparks in the nearby trees that their service feed was routed through. When I looked at the feed I saw that a hot leg and the neutral leg were severed in two seperate locations, 27' and 90' from the transformer. The breaker panel was heavily damaged leaving the main breaker in such a condition that I cannot determine its final position. One of the load side connectors on the meter base was also heavily damaged. Now for the $50 question - could a problem in the meter base or service panel overload the line enough to melt the insulation or did a fault occur in the trees shorting a hot leg to neutral and creating an energized neutral in the breaker panel?

The money's on the latter scenario

Thank you

 

[K8MHZ]

I investigated a house fire yesterday that appears to have originated in the breaker panel. When the occupants went outside after being awakened by their smoke alarm they noticed sparks in the nearby trees that their service feed was routed through. When I looked at the feed I saw that a hot leg and the neutral leg were severed in two seperate locations, 27' and 90' from the transformer. The breaker panel was heavily damaged leaving the main breaker in such a condition that I cannot determine its final position. One of the load side connectors on the meter base was also heavily damaged. Now for the $50 question - could a problem in the meter base or service panel overload the line enough to melt the insulation or did a fault occur in the trees shorting a hot leg to neutral and creating an energized neutral in the breaker panel?

The money's on the latter scenario

Thank you

You are asking us to decide (guess) whether or not something could have happened or if something did happen.

What does the evidence show?

 

[480sparky]

About txaggie84
Location Chattanooga, TN
Interests Radio Control Airplanes, Fishing
Occupation Forensic Engineer
How are you related to the electrical industry? Perform electrical investigations at loss sites (fire, water, etc)

Strange. Very strange.

Is that what you do for a living, or are you just being asked 'to look at it'?

 

[don_resqcapt19]

With heavy damage to the main breaker, based on the very limited information you provided, I would guess the problem originated on the load side of the main.

 

[infinity]

Some photo's might be helpful.

Welcome to the forum.

 

[txaggie84]

Here are some pictures. We are going to recover the breaker panel and meter base on Monday (11/23). We did not want to remove the cover "in the field" as all the breakers are very fragile. The cover is also welded to the box so it is going to take some effort to get it off. Only two of the branch circuits fed from the panel showed signs of damage (beyond melted insulation) and their damage appears to be from heat impingement and not electrical arcing.

Feeder break #1

Feeder Break #2

Service Panel

Conductor arcing to service panel

More conductor arcing

Load side receptacle on meter base (the other side was undamaged)


We investigate a lot of fires caused by bad wiring, high resistance connections and appliance malfunctions but don't see many feeder faults or service panel faults of this magnitude.

Thank you
Aggie

 

[LarryFine]

I can't help but wonder whether there was a primary-to-secondary contact which overstressed the insulation.

That just doesn't look like 120v-to-ground damage.

 

[marti smith]

aggie, please post your findings- thanks!