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Old 21-11-2014, 20:59   #1
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Fire if improper electrical connection?

Could it cause a fire if the wind generator wire has only a quarter of it's positive electrical connector attached to the battery?

Could it cause a fire if any electrical connection simply didn't have enough contact in a 12-volt system? I'm not talking about sparks near gasoline fumes or propane in the bilge, but something causing the wires to get hot, or the batteries to melt or the wire insulators to melt... I'm not talking aboug shorting the battery wires. That seems obvious to me, but, what about the less obvious stuff. Perhaps there's possible fire hazards w/ batteries I'm not familiar with. Wouldn't most poorly connected devices simply draw less overall power and not heat something up, or is that wishful thinking?
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Old 21-11-2014, 21:17   #2
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Re: Fire if improper electrical connection?

You bet. Crappy insulation will start smoking and then combust.
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Old 21-11-2014, 21:37   #3
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Re: Fire if improper electrical connection?

Umm...., insulation is specifically designed not to catch fire, but with some of the cheap stuff around theses days it could be a crap shoot now. An issue would be an appropriately named "hot joint" causing the insulation to heat up enough that it melts away, exposing a hot wire or joint to a combustible material. I've never seen a hot joint set fire to anything (and I used to work everyday with high output DC welding machines for many years). It either takes a wire glowing red with heat or sparks to start a fire. Having said that, it is very possible that a bad connection could emit sparks in the right set of conditions though it would be unlikely to glow red unless there is a short circuit, which I guess could happen if an exposed wire were to fall across another circuit creating a short.

One odd thing that happens when a wire melts it's way out of insulation is that it falls out of the cable, which can be dangerous, obviously, but it would still take a gross overload of the conductor for this to happen.
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Old 21-11-2014, 22:13   #4
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Re: Fire if improper electrical connection?

yes here is some pics from 1-2 months ago. bad connection at electrical device caught boat on fire. luckily person was on board and put out with fire extinguisher. wire was on a breaker which did not trip.

red was cut by owner. neg is melted away


you need something near by to burn. I doubt anything is close to a battery terminal to burn. but elsewhere in the boat for sure.
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Old 21-11-2014, 23:27   #5
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Re: Fire if improper electrical connection?

I would go as far as to say that the vast majority of electrical fires is caused by poor connections!
This is not limited to DC circuits.
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Old 21-11-2014, 23:55   #6
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Re: Fire if improper electrical connection?

You are correct in assuming that with a voltage source and a high resistance series connection the current flowing will go down, but the high resistance connection will get hot. The load resistance is also part of the equation. Question is which condition wins out and plenty of high resistance connections have started fires.

In a current source situation (battery bulk voltage charging phase) then the source voltage will rise in an attempt to keep the current at a certain level. Obviously this type of set up can also cause a fire.
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Old 22-11-2014, 00:55   #7
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Re: Fire if improper electrical connection?

Quote:
Originally Posted by liveaboardL View Post
....... Wouldn't most poorly connected devices simply draw less overall power and not heat something up, or is that wishful thinking?
What Frankly said +1

It is wishful thinking!

A poorly connected device often draws less current but creates a lot of heat. Heat is a function of power which is a function of volts and amps. A good connection has a low resistance so has a low voltage (or PD - potential difference) across the connection so has low power dissipated in the connection. A bad connection (due to say corrosion) has a higher resistance so has a higher voltage (PD) across the connection thus has a higher power dissipated in the connection. This is bad as the connection is never designed to have high power loads developed in them.

The first symptom of heat build up is usually a "burning smell", the second is smoke and the third is flames.

Often smoke is enough to cause problems and it doesn't take much heat in the wrong spot to create a shipload of smoke.

A couple of weeks back, a flight crew made an unscheduled landing due to a significant amount of smoke generated in the cockpit from a bad connection in an instrument light. So only a small light and one bad connection generated enough heat to cause the paint to smoke and fill the cockpit. In the end analysis, there was never enough heat to start a fire or cause serious issue but they didn't know that at the time.
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Old 22-11-2014, 01:03   #8
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Re: Fire if improper electrical connection?

I don't want to sound mysterious, but I'll vouch for Wottie knowing what he's writing about, FWIW.

Ann
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Old 22-11-2014, 01:30   #9
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Re: Fire if improper electrical connection?

Quote:
Originally Posted by Ann T. Cate View Post
I don't want to sound mysterious, but I'll vouch for Wottie knowing what he's writing about, FWIW.

Ann
FWIW - I luv it when Ann sounds mysterious
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Old 22-11-2014, 16:07   #10
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Re: Fire if improper electrical connection?

CLEAN AND TIGHT CONNECTIONS ALWAYS...
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Old 22-11-2014, 16:26   #11
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Re: Fire if improper electrical connection?

smac999 photos are a perfect example of how important it is to treat the Neg wiring with the same respect as the Pos.The same current flows in both Pos & Neg.
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Old 22-11-2014, 19:09   #12
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Re: Fire if improper electrical connection?

Definitely 12 volt shorts can cause problems. I was helping an engineer change out a Gel battery on a 47, managed to cross the terminals with his thumb wrench and it actually deformed the crescent wrench along with a lot of sparks, cursing and a little smoke.
A/C wise, I've cooked a few shore power cables with bad connections. One, cooked on the boat connector side. I was out, cabin filled with smoke. Wife called my neighbour who unplugged at the other end.
All these threads about the risks of CO poisoning from various types of burner heaters, but, I've had my share of scares from electric heat.
Remember when cars had cigarette lighters instead of Bluetooth?
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Old 22-11-2014, 20:00   #13
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Re: Fire if improper electrical connection?

Quote:
Originally Posted by Wotname View Post
What Frankly said +1

It is wishful thinking!

A poorly connected device often draws less current but creates a lot of heat. Heat is a function of power which is a function of volts and amps. A good connection has a low resistance so has a low voltage (or PD - potential difference) across the connection so has low power dissipated in the connection. A bad connection (due to say corrosion) has a higher resistance so has a higher voltage (PD) across the connection thus has a higher power dissipated in the connection. This is bad as the connection is never designed to have high power loads developed in them.

The first symptom of heat build up is usually a "burning smell", the second is smoke and the third is flames.

Often smoke is enough to cause problems and it doesn't take much heat in the wrong spot to create a shipload of smoke.

A couple of weeks back, a flight crew made an unscheduled landing due to a significant amount of smoke generated in the cockpit from a bad connection in an instrument light. So only a small light and one bad connection generated enough heat to cause the paint to smoke and fill the cockpit. In the end analysis, there was never enough heat to start a fire or cause serious issue but they didn't know that at the time.
Here's a perfect example, Swissair Flight 111, 2 September 1998, an MD-11, 229 dead, downed near the entrance to St. Margarets Bay, Nova Scotia:
Swissair Flight 111 - Wikipedia, the free encyclopedia

Fire quite probably began in a likely low voltage circuit (doubt that any higher voltage leads are routed between system components) near the cockpit:

"Investigators identified evidence of arcing in wiring of the in-flight entertainment system network, but this did not trip the circuit breakers. The investigation was unable to confirm if this arc was the "lead event" that ignited the flammable covering on MPET insulation blankets that quickly spread across other flammable materials.[1] The crew did not recognize that a fire had started and were not warned by instruments. Once they became aware of the fire, the uncertainty of the problem made it difficult to address. The rapid spread of the fire led to the failure of key display systems, and the crew were soon rendered unable to control the aircraft. Because he had no light by which to see his controls after the displays failed, the pilot was forced to steer the plane blindly; intentionally or not, the plane swerved off course and headed back out into the Atlantic. Recovered fragments of the plane show that the heat inside the cockpit became so great that the ceiling started to melt."

We've all seen electrical connections that have gone bad, sometimes just looking a bit 'overheated/discolored', sometimes outright fried.

I've only had one incident where the item went up in smoke, and it was spectacular (I can say this now). It was one of those Cadillacs somebody was complaining about, one of the best vehicles I ever had, but I had gotten over 400K miles from it and it must of had enough ;] .
Going down the interstate, smoke started coming through the A/C vents and from the hood, ruh-oh, note to self: this is like one of those WWII air war movies. Pulled over ASAP and quickly decided that I had better get my stuff out of there pronto. Made a number of trips emptying my luggage, etc., as I watched the progress of the blaze from the engine backwards (a port quarter crosswind kept the smoke away from me, I bailed when it got closer to the almost full fuel tank :] ).
Never knew what the root cause was, but the starter had been changed some time before.
This vehicle had also caught fire once (minor) when a mechanic checked the TBI fuel pressure by cracking/bleeding a fuel line access port-- next to the distributor while it was running...
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Old 24-11-2014, 10:48   #14
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Re: Fire if improper electrical connection?

Quote:
Originally Posted by smac999 View Post
yes here is some pics from 1-2 months ago. bad connection at electrical device caught boat on fire. luckily person was on board and put out with fire extinguisher. wire was on a breaker which did not trip.

red was cut by owner. neg is melted away


you need something near by to burn. I doubt anything is close to a battery terminal to burn. but elsewhere in the boat for sure.


Wow thats a bad burn. Looks like an E-plex module if you need any help with that let me know.
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