Another Bird fire

[Ralph Fullenwider]

Excellent rebuttal Bob, and the high resistance shorts can, proved my Ron's
Coach, like an electric burner on a stove, before burning in two.

Safe travels,

Ralph & Charolette Fullenwider
'84 FC 35 "Ruff Diamond"
Duncan, Oklahoma

At 12:35 AM 11/28/2009 +0000, you wrote:
>Exellent comments Pete, but readers should be cautioned that fuses in high
>amperage cables may not provide complete protection. Consider a 200 amp
>fuse placed to protect a main DC supply cable. An insulation breach can
>start slowly and generate a great deal of heat without popping the
>fuse. In areas where engine heat, oil, and abrasion are present, the
>resistance of insulation can break down and start generating heat long
>before there is a full metal-to-metal short. By the time the breach gets
>bad enough to pop the 200 amp fuse enough heat may have been generated to
>start a fire.
>
>Fuses are very important, but vigilant inspection is a must for safety.
>
>Bob Griesel '84 FC31 WLII WA
>
>
>--- In WanderlodgeForum@yahoogroups.com, Pete Masterson wrote:
> >
> > I think it should be pretty obvious that all high-amperage, unfused
> > battery cables ought to be checked carefully.
> > That would include the house batteries -- in a '95 those are contained
> > in the rear-most curb-side compartment and on a tray by the engine. In
> > addition, there are 3 engine batteries above the 2 house batteries
> > near the engine.
> >
> > The house batteries are wired to a general distribution panel on the
> > curb side of the firewall. The engine batteries are wired to the
> > engine -- but also have a connection to the house batteries (as you
> > can tie them together with a switch on the dash).
> >
> > The Bakersfield fire _might_ have been caused by a short from the
> > house batteries and/or the firewall distribution panel. (We await
> > further word from the fire inspector and/or insurance adjuster.)
> >
> > Randy's fire was caused by a dead short in the front most, street side
> > compartment, where the battery cable (running 40-some feet from the
> > curb-side rear to the street side front-most compartment) that serves
> > the generator starter motor. Apparently, from the report of the fire
> > inspector and insurance adjuster, it appears that the insulation had
> > been compromised where the heavy cable passed over a frame rail.
> >
> > We all may have been a little complacent over the 12v systems, since
> > 12 v current rarely causes much of a fire or electrocution issue. It's
> > easy to forget just how much potential amperage that the batteries can
> > release in a dead short.
> >
> > The suggestion to install a high-amperage (slow acting) fuse on the
> > batteries makes a lot of sense. A slow acting fuse is required since
> > things like the engine and generator starter motor can draw a brief,
> > very high amperage burst -- and you don't want to blow the fuse. But a
> > short would cause a longer drain, and would blow the fuse.
> >
> > Of course, a careful inspection of all the high-amperage wires is
> > called for. Unfortunately, wires may pass through areas where visible
> > inspection is difficult or impossible. (Mirrors mounted to extension
> > handles and flashlights would be quite useful.) Even so, it's likely
> > that there are places where thorough inspection will prove impossible.
> > (Which simply increases the importance of fusing the batteries.)
> >
> > Another 'wise' modification would be to install a high-amperage switch
> > to completely isolate the batteries from the coach. Marine supplies
> > sell such switches for boats and they can be adapted to motorhome use
> > quite easily. The added advantage of such a switch would be to ensure
> > that all phantom loads (which BBs have in abundance) would be cut off,
> > allowing longer storage periods without a charger on the batteries.
> >
> > In the Bakersfield situation, it's hard to discern how the fire might
> > have been avoided. The owner reported that he'd inspected the wires
> > (as best as he could) after hearing about Randy's fire. It is unlikely
> > that any of us would have shut off all the batteries while in a nearby
> > restaurant for dinner -- but fuses _might_ have saved the coach, had
> > they been installed. (Then, again, pending a final determination of
> > the cause of the fire, it might not have been effective.)
> >
> > Pete Masterson
> > (former) '95 Blue Bird Wanderlodge WBDA 42
> > El Sobrante CA
> > aeonix1@...
> >
>