House fire

[Chad Fabry]

As a fire marshal, I enter just-put-out burned homes. Often, it's clear what caused the fire- oily rags in the garage, bad wiring etc.

The fire today was clearly caused by the large TV-giant hole in the floor below the TV and a burned out stair case behind the TV. The service panel also burned but the fire was contained inside the panel.

Just before the fire, a car struck a pole with a pole mounted transformer and the lineman who was repairing the transformer noticed smoke coming from the home. The transformer served this house and three other homes on the street.

Luckily, the owners were not at home. The four cats were not so lucky.

What could have happened that sent a surge powerful enough to smoke the service panel and start the TV on fire?

Tomorrow, I'm buying and installing a whole house surge protector.

[kurt]

What make and model?

[Scottpat]

Wow, some things you just never think about. Who would have imagined that something like that would happen.

[Ben H]

I was looking at this one last week, but I really don't have a clue what makes a good one. http://www.amazon.com/Leviton-51120-1-P ... B00081K55Q

[Bill Kibbel]

What could have happened that sent a surge powerful enough to smoke the service panel and start the TV on fire?

When the pole was hit, the higher voltage line made contact with the lower voltage distribution line below. 120 V can become 300 V.

Tomorrow, I'm buying and installing a whole house surge protector.

If the overvoltage occurs for any significant duration, it can fry surge protection varistors.

[John Kogel]

A surge hit the panel and then the circuits a millisecond later.

The TV was left on. The other appliances were off or robust enough to take the surge.

What age of TV? Did it have a picture tube that may have exploded? If a new one, it was full of combustible plastics and thin filament wiring in plastic strips.

This is why I tell people missing knockouts in the panel can be a fire hazard. I have seen electricians repair their wiring mistakes and ignore the missing knockouts, like they are no big deal.

[Marc]

I'm with Bill except that 120V to ground can become 8,000 volts to ground (for 13.8KV distribution schemes) for several seconds until some breaker further upstream opens up and then there are inductive currents that are generated when high currents are interrupted that can exceed 8K easily (that's how old CRT picture tubes got the high voltages needed for the picture tube).

The xformer primary leads aren't so far away from the secondary lines on those pole mounted transformers.

Also, the 8KV could have made it's way into the home via any of the three conductors. You might not get as much on the neutral because of it's better connection to the earth but there'll still be plenty enough juice to cause trouble.

If the tv was turned on at the time of the event, the path for the distribution-level voltage was there, not that its needed.

As Bill opined, this type of failure would toast any surge protector instantly, in fact, it'll toast anything in its path, EGC, etc

You should consider the integrity of all four electrical installations suspect now. All circuits in those 4 houses should be megger tested before they are returned to service.

Marc

[Rob Amaral]

Our friends had a 30 yr vintage pole transformer 'go south' in their neighborhood to their dismay (and their neighbors)..

Surge protector was installed later..

I have one on my house ... I can't abide me old Fender amp getting fried due to this..

[plummen]

Power surge and an open neutral.

[John Kogel]

Surge protector was installed later..

I have one on my house ... I can't abide me old Fender amp getting fried due to this..

Rob, you should pull the plug when you are not using it.