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Joined: Oct 2004
Posts: 806
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jdadamo:

Generally speaking, an overloaded circuit would tend to have excessive voltage drop which is enough to cause a motor to fail. Most motors will not start or draw excessive current if the voltage is much below 85% of nameplate (>15% voltage drop).

And since a motor starting can create a voltage drop, the freezer's motor in this case would be making a bad situation worse.

This type of tragedy is one I've read of too many times. Family smells smoke, fire dept. comes, finds nothing, leaves, hours later a blaze starts. Many times cause was later found to be electrical.

I have a friend who is a firefighter, I will ask him if the fire dept's. training covers detection/recognition of the unique nature of fire started by overloaded electrical circuits/equipment.

My hunch here is that without tearing open walls, etc. the fire dept. really has no way of verifying possible ignition sources. IF the dept. happens to have an IR camera device (I saw one in use at a smoke call in a $75 mil. mansion I was working in) they might have found the potential hazard. Otherwise it would be a matter of the firefighters seeing visible signs of smoke/fire or being in the right place at the right time as it were.

In the mansion call, it was determined that an air handler motor burned out. Even though the caause was found, the fire chief reccomended that the staff maintain "observational" status for at least the next six hours and immediately call in anything out of the ordinary.


Stupid should be painful.
Joined: May 2003
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e57 Offline
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Partially un-related story:

I walked out of a job-site one day to find the whole street crawling in Fire-fighters, on ladders, on roofs, wandering in and out of buildings. I'm talking 10+ trucks, and nearly 50 guys. After a few minutes, I had to ask, "wheres the fire?" One of the guys just says, "Well we dont know, we got a call for smoke, and when we drove up here, there was smoke, lots of it, not sure where it came from, and we get here, NO SMOKE!" After an hour they figured it was a resturaunt hood duct, that had self extinquished. I guess they found soot instead of grease in it, and warned the resteraunt manager to get it looked at. Next day at lunch time the thing went up like a charcoal starter. I guess the guy didn't listen.

Back to thread though, I have seen 20A FPE's hold almost 40A, and not trip on dead shorts either. Then again I have seen this with other breakers too. A lost neutral can do some wierd things too. 220v on the freezer motor, or anything else could ignite it as well.

And just because the Fire Dept. was there, and didn't find anything first time around, because they didn't tear the house apart, these people knew something was wrong. Dare I say it, although it is tragic, putting blame on the fire dept. for something like this is just more of the American disease of 'find someone to sue'. As I am sure if they knew where the smoke had come from on the first call, they would have done something about it.


Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Nov 2004
Posts: 37
J
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mxslick thanks for the explanation. I forgot about the role voltage drop might play in this scenario.

Joined: Jan 2005
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Cat Servant
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Even assuming that the fire was started by the appliance....and it may very well have been, with the smoke dissapating until the next refrigeration cycle, when the insulation ignited, etc....I can only note one thing:

SMOKE DETECTORS HAVE BEEN AVAILABLE FROM THE MID SEVENTIES! Now, tell me which is cheaper (and more likely to be useful)- an $8 battery powered smoke detector, or an attorney's retainer?

Even small amounts of electricity can start a fire...my toaster is a good example of this. Breakers respond slowly to small overloads. You can weld, for heavens' sake, with what comes out of a 20 amp receptacle.

Perfection is something found only in the next world.

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Quote
Fire officials who investigated and dismissed a smoke call at a New Jersey home that later erupted in an inferno, killing four children, fear the family will hold them responsible for the tragedy.

"I'm sure there'll be litigation," one official said.
I find it rather strange that a Fire Department could be held responsible for an overloaded circuit.
Heat imaging equipment or not, just how far do you have to go?.

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