Hello Friends.
This past weekend we had a mobile home fire, caused by a "comedy of errors" both electrical and human. HO had been having trouble with the power switch on a small window unit air conditioner. He shorted the switch, thus allowing the unit to run continuously. More problems followed, with the breaker for the AC circuit starting to trip periodically. HO's solution to this was to tape the CB in the ON position. At some point after this, HO woke up to the smell of smoke, and investigating, discovered a small cabinet beneath the AC unit on fire, having been ignited by the nearby wall receptacle. When our first engine company arrived, we found the wiring in the wall in a state of meltdown. Not being able to immediately located the breaker box inside the mobile home, a firefighter disconnected power at the main switch under the POCO meter. The breaker panel was eventually found (hidden behind a closet door), and one of the breakers was indeed taped in the ON position - the firefighter who located it also told me that it was very warm as well.

Regrettably, I did not get to see first-hand what brand the breaker panel was (I was chauffer/engineer for the company). I always thought that circuit breakers would trip internally, no matter what was done to the exterior operating handle, and it might be that this breaker suffered some form of damage from repeatedly tripping and resetting, and eventually "welded" itself in the ON position.

Are any of y'all familiar with any brands of circuit breakers that will NOT trip if the handle is physically restrained, as in this case?

Mike (mamills)

PS. I thought this might be an FPE-type incident, and to that end, I showed the captain of our crew an old FPE breaker I had laying around in the trunk of my car. He denied that the breakers in the panel looked like the FPE.

The requires breakers to be "trip free". That means they will trip when held in the on position. We demonstrate this by placing a breaker lock on a breaker and slamming it on the table ... it trips. This ends up costing us a breaker about every 3rd slam but it makes the point. Of course there's no telling if the breaker in question was either defective or old (I don't know how long the trip free requirement has been in the code).

Nearly all "Commonly Used Basic" Circuit Breakers for use on 240 VAC Max. systems, with frame sizes of 100 Amps - maybe as large as 225 Amps, these are "By Default" Trip-Free design.

Trip-Hold devices are special order items, but that does not mean it will not be used by "Joe Jackleg" in an incorrect application!
(Read:"I found this breaker _______, so I will use it for this Mobile Home Install")

***NOTE*** fill in the above blank with one or more of the following:
"at work" / "at some demolished Industrial location" / "in the dumpster" / "on the shelves of the local distribution center" / "in some EC's truck" / "in some panelboard"



Could have been a Trip-Hold (Non Trip-Free) breaker, but chances are more likely the Breaker either was:
Closed too many times with a fault on the circuit (fusing the contacts closed),
The breaker had been reset so many times the latching spring came loose; preventing a trip,
The Breaker was replaced with a higher rating type (60 amp instead of the original "nuiscance" 20 amp) + for redundancy, tape was applied to the handle to "eliminate those pesky trips",
or lastly,
The Cord/Receptacle connection was just too warn out and generated so much heat, it finally caught something on Fire.

Scott35

Source of ignition was at the receptacle.
Breaker with tape on handle may have been defective and contributed. However it was tripping earlier, and the failure at the receptacle may not have been enough to trip it again. Tapeing a handle should not prevent a breaker from tripping.

Why did smell of smoke and not smoke detectors sounding wake the occupant ?

NOTE; HUD allows Mfg. Housing to have the panels located in closets if two feet above the floor and accessable, not behind the hanging clothes.
Alan--

Alan:
The engine crew that entered the mobile home said that there was a smoke detector, but that it was not functional. Judging from the outside appearance of this home, the HO was not real big on maintaining the property.
The captain told me that the breaker panel was located in a bedroom (actually within the bedroom space), hidden behind an open closet door, with a couple of boxes against the door.
The HO told us that the breaker had tripped "several times", which led to the tape. I do not know how long the circuit held closed each time (except the last, of course), but I tend to go along with Scott that something mechanically went wrong with the breaker from reclosing it into whatever kind of fault condition was imposed by the air conditioner. Since the origin of the fire was the wall receptacle, and it (along with a decent portion of the wall around it) was consumed by the fire, I could only guess that this became the "weak spot" in the circuit, instead of the breaker. When the breaker panel was located during overhaul, the handle of the breaker was still taped in the ON position (and was still warm to the touch). I'm assuming that a fault of much lower impedance occurred when the insulating material in the wiring and receptacle melted away, but the breaker was still on (due to the sparking and flaming that was still occuring on our arrival). The fault did not clear until the firefighter disconnected the service at the main circuit breaker outside.

I have seen many breakers taped in the ON position. I have also seen devices (Square D comes to mind) which can be attached to a breaker handle in either ON or OFF position to prevent the HANDLE from being operated.

Mike (mamills)

Sounds like the breaker may have failed. However I don't think the tape had any bearing on the failure, except to indicate which breaker was at fault.
One thing to check is that most mobile homes do not come equipt for an air conditioner. It is usually added in the field. Many HVAC installers will use whatever brand breaker will fit in the panel regardless of listing. Bryant, GE, SqD HO, etc. While they seem to fit they may cause problems, or fires.
I any case it goes down as a fire of electrical origin as if an electrician could be blamed.
Alan--

-John

[This message has been edited by BigJohn (edited 04-26-2006).]

John: I quite agree. I think the people that lived here were not really at the top of the food chain. They certainly did not know how to properly handle the situation that was at hand - beyond calling 911 when the going got rough.

Alan: The air conditioner was a small 110v. window-type unit. There appeared to be no special circuit installed for it, but was connected to a nearby duplex receptacle intended for general use. There was also another air conditioner (very much in size and appearance to the first) in the back bedroom (and connected in the same manner), where the breaker panel was found.

Anybody for chapter two... ?

Mike (mamills)

[This message has been edited by mamills (edited 04-26-2006).]

I believe that older breakers did not have the ability to trip when held on; that came along later. In other words, how old is this equipment?

Hi Larry:
Can't say for sure how old the panel is - I never actually saw it, or the breakers. I would have to guess that the mobile home dates somewhere back to the mid 60's, and that the electrical equipment is/was original.

Mike (mamills)

Federal Pacific? Well known not to trip...

This is anecdotal, because I don't rememeber who made the equipment: But I've run into a couple panels in a junior high-school where holding the breaker handles in the "on" position would keep them closed even during a severe OL.

Found this out one of the teachers demonstated how they tried to get a tripping breaker to "hold". It was a circuit to a fan with a locked-rotor, the guy held the breaker handle closed and looked at me going "See? It just won't stay for some reason." while the breaker hummed and crackled and started spitting sparks.

-John

That's a prime example of a Darwin Award candidate. Try that cute stunt with the fact that POCO's have updated transformers and feeders to meet the higher demand, which makes the available short circuit current a lot higher (probably higher than the older equipment was designed for) and you're more likely to have that breaker explode in your face!! Followed by the entire panel going up.

That's why I always stand to one side and don't look at the panel when actuating breakers, fault or no fault.

The first actual NEC requirement that circuit breakers be "trip free", that is trip regardless of handle position, was in the 1975 Edition.

All the breakers I remember were that way anyhow.

That reminds me of the way I was taught old-timers located faults... burning them out by inserting a way larger or even blank fuse (take 50 amps instead of 10 or a solid aluminum fuse blank)...