Fire in motorhome ( extra lucky )

[John Bagwell]

Dave   Glad you and Pat are ok.  Motorhomes can be replaced.  Hope repairs can be made and get things back to normal. 

[Dave Atherton]

Bill and Ed, something that caught my attention with Bill post about the use of wire nuts
and applying wire nuts ( either not tight enough or way too tight. ) the correct install and
use black tape to keeps wire nuts tight. There was so much going on cannot tell if breaker
tripped or did not trip but I did not trip the breaker so if it was tripped the fire dept shut off
the power. Electrician mention if wire nut were loose the joint would create heat, it still
spooks me fire started in a metal junction box and transfer of heat started the plywood on fire.
Dave

[Edward Buker]

Dave,

It is not hard to imagine a loose connection at a wire nut in a motor home with the years of vibration during travel. I have tightened or replaced a few. The junction block within my genset had a loose connection this year that put one leg of 120V down. Being watchful for any flickering or brownout is your best bet as a telltale. On top of all the vibration there is corrosion to ruin a good day.

Like you Dave, I would have not have suspected that a short would have continued to do welding inside the box without tripping a breaker in the chain. If shorted, the short heated the box, and the box started the fire, or the grounding connection point of the box caused the heating. The box being metal, by code would have to have been grounded and that should have caused a breaker to kick if it was a good ground connection.

Check the box and see if the box looks like it was well grounded, if there is enough left of it. My best guess is that the ground path was resistive enough to cause heating but not good enough to conduct the amperage that would trip the breaker. Much like a toaster using nichrome wire, there is a resistance that works for heating without being a hard short.

There have been times that just the poor contact of a conductor point like a wire nut, heats enough under load to get very hot, but it is hard to imagine that situation creating enough heat within a metal box to have the box itself cause a fire. Puzzling one for sure...

Later Ed

[Dave Atherton]

Ed, being electricity is not my area and reason I'm spooked at present. What I can relate
so far, fire dept determined cause of fire pointed to junction box starting plywood, electrician
said fire started with wires shorted in junction box. I passed these thoughts on to the insurance
adjuster not moving things around until he makes his review. Back to you Ed, reading your
last post along with Bills post. Looking at junction box with cover still off can see a wire that
fasten to the box at back and is about 6 inch long that makes a half loop and end of wire is
stright, this must be the ground wire you mentioned that is wire is not bent or twisted like
it made a connection. My next question again this junction box was screwed into the plywood
behind the junction box that caught on fire. There 3 wood screws laying loose in the junction
box. Little about electricy that I do know plywood would not make a ground or would could it.
The only heavy electric use comes from the A/C everything else is the low power 12 volt lights,
and we eat out all the time so we do not use any hot plate, crock pots or electric heater when
cold. If we use a electric heater we run a spearate heavy cord from a outside sourse and nothing
inside of motorhome. Again the nice part of this forum and background of membership there is so
many areas of experience. ( with information posted it looking problem was present and left the
factory with problem ) someone had to be sleeping. This motorhome has never had any work
done to it except shifter board on transmission. Will see what the insurance adjuster thinks about
this Monday. Again guys thank you, as I been saying this really has spooked me. Dave

[Bill Sprague]

Dave, I'm glad you and family, furry too, are OK!!!  I hope the insurance takes care of it the way they should!
Bill, how do you even get in where the elec. hose real is?  I'm afraid to even think about it that going bad!
Jerry

Jerry,

On mine (now Rick's!) the reel was in a bay where it was accessable.  Unfortunately for Rick (!) the plastic gears in the reel failed about two years ago.  Rather than replace it, I hardwired the cord to the transfer switch.  Rick now has to coil the wire the old fashioned way!  As I recall, the transfer switch had no wire nuts.  It used clamps like in the distribution breaker box.  That kind of clamp should not be an issue.  So the run from the inlet wire to the distribution panel would not have the wire nuts anywhere.

I think Dave's fire was in the kind of J-Box where stickhouse wire nuts were used.  I think the suggestion is that one of the wire nuts may have come loose allowing contact with the grounded J-Box.

[Joel Ashley]

From Dave's description of that junction box, it sounds like there may be no ground connection through to the Mains inside the coach.  Nevertheless, the fault should have blown the breaker at the post outside;  those in my experience are often faulty. 

Factory personnel, as we all know, commonly drop wire ties and screws without taking time to retrieve them.  But 3 screws at the bottom of a small j box implies a very clumsy or incompetent employee, or a poor repair or retrofit by someone later - perhaps an indication of an unprofessional attempt at wiring also, and by inference the wire nut scenario others here have experienced.

The scary thing that should indeed spook Dave is if there is no metal conduit between the j box and the 50 amp main box inside, or no modern wiring to it in lieu, then theoretically he never had complete ground protection for any device or appliance in his coach.  The wire he's seeing could be from either the Main end or the cord end.  Sans metal conduit, I'd expect to see two wires grounded to the box, not one.  It's probably simply the cord ground, thus the arcing to the box from a bare hot lead.  The post breaker may have tripped, just not before sparks caught some debris that smoldered ultimately into the plywood structure behind.

Otherwise if the j box got hot enough to ignite the wood, then you'd think there was enough errant current to have kicked the breaker before that it got to that point, and I'd point at a faulty post breaker as contributory.

Reckon we'll have to reserve judgement for all this until an electrician clues him in more.

Not sure why the electrician did say heavy AC use affected it, if it was a direct short within the j box.

Joel

[Dave Atherton]

Joel, thanks for your word of wisdom. Checking at shore power post. Reading on tester
120 volts @ 18 amp, before fire power cord 25 feet. Inside where power connects to
motorhome is 30 amp. The junction box is screwed into plywood 1/4 thickness with 3
wood screws. Which are still in burn't junction box loose. As I was saying in eariler post
some thing Ed mentioned and I followed up on ( ground wire fasten to junction box ). The
answer was yes I found a 6 inch wire in half circle, one end connected to junction box and
other end was stright not twisted or bent, which would appear nothing was connected to this
6 inch wire fasten to the junction box .as I mention eariler I did not shut off power because
I was using fire ext.when fire dept pulled up. With everything going on the fire dept could
have shut off power. Kinda busy for a while. My motorhome is a 2010 and recourse would
be next to none if factory messed up with time frame behind us. Where I'm going with all
this if a fire started by electrical cause and not knowing what cause, am I going to chase the
problem some place else to happen again. Not knowing anything about wiring, wire nuts etc.
junction box just screwed to plywood or ground not being connected, I would be nun the wiser
something was not connected correct. Thanks for come back Joel Dave

[Joel Ashley]

Okay, I think I understand that wire now.  Sounds like it was simply a bare copper pigtail meant to go from the wire nut to ground the box.  The wire nut likely tied together that pigtail and the copper/green wire from the cord and the one going from the j box to the Surge Guard transfer box.  I thought, actually, the cord went directly to the Surge Guard, with clamps like Bill mentions, but I don't have the coach right in front of me to confirm one way or the other.  That aside, the wire nut in your j box may have been removed by a fireman or the electrician after the fire for some reason.

Otherwise the short could've been from the nut coming off and that wire's free end contacting one of the hot leads.  If properly wire-nutted and tucked correctly and carefully in place inside, none of these wires should have made any unintended contact with anything else in the box.

My father was a station wireman for Pacific Power, and built control panels for our Northwest dams.  I didn't learn a whole lot from his electrical expertise like I should have, just what I could when I finally got old enough to know it was important.  By then he was soon taken from us, so I only know some basics and what I got from books and the "code" publications;  I'm certainly far from an expert.  Others here have a much better understanding of such things, and I very much envy that.  I don't blame your anxiety around electricity, but have found respect for it to be a better companion than fear.

Keep us appraised, Dave.

-Joel

[Bob Jae]

I have recently started using connectors made by WAGO many of them are UL listed and much more secure than wire nuts.
http://www.wago.us/products/terminal-blocks-and-connectors/overview/
Many are shown at this link.

[Joel Ashley]

Thanks Bob.  The Wago 51015200 at Amazon looks like a good option if you need them only rarely, and there is a 50-pack also;  a 10-pack would be my preference.  I have a shop mini drawer full of wire nuts already.  The Wago lock lever style looks more reliable than the similar push and twist ones, also seen at Amazon.

My only negative thought is that a 3-connector Wago looks to be bulkier than a simple 3-wire wire nut;  it might prove a tad harder to fit several (most commonly 3) in an outlet or switch box for example, along with 6 or more folded wires.

Joel

[Edward Buker]

Dave,

I think that in order for the box to get hot enough, it was likely in the circuit, that is a hot lead on one leg contacted the grounded box that did not produce a dead short. In order for this to support combustion I believe that the ignition source had to reach between 450F and 1100F. What is clear is the old box was not wired properly, the connections were not tight, whether it was a short or a loose connection that heated is not too important, it was one or the other and it got very hot from the load.

Dave I understand your nervousness but this wiring can be done safely and properly so that something like this cannot occur. In order to set your mind at ease, focus on what is the plan for the repair. Here are some thoughts.

1. I would have a metal box for the repair that gave enough room for an electrician to work.

2. I would have a piece of some insulating non combustible material like a piece of cement backer board between the box and the plywood for remounting if possible. It does not have to be much bigger then the interface between the box and the wood. Maybe the box size plus an inch if it will fit.

3. The box needs to have proper clamps to secure the cable.

4. The connections can be a form of properly sized butt splices with screw terminals or crimped type butt splices, or the correct size wire nut, tightened properly, and well taped to prevent loosening. If crimped butt splice the proper tool needs to be used to assure that the crimp is set properly.

All of these methods are good solid connections when done properly. Observing the job and the care used, inspecting the final result (check the tightness yourself of each wire nut before being taped off), will go a long way in bringing back piece of mind. Before covering the box, run the air conditioners, add some heavy loads for a bit and feel each taped wire nut to assure there is no heating taking place. Connections should be no warmer then the wire. You now know it is done right and can be covered up.

Piece of mind will come from having the job done right and a little healing time...

Later Ed

[Edward Buker]

We are talking 6GA to 8GA wire most likely and 30 to 50 amp service in this application. The Wago connectors look light duty and I would not want anything with a flip lever in a vibrating environment. Not sure if they make connectors that are more substantial then these appear.

Later Ed

[Steve Huber Co-Admin]

Ed,
They are a pretty robust connector and really handy for connecting multiple wires. HD (and maybe Lowes) carries them. Since the opening for the wire is sized, it prevents one from putting too large a wire gauge in and thus reducing the closure tension. Check them out.
Steve

[Edward Buker]

Steve,

I will take a peek hands on sometime when I am in the store. When you are looking at 50 amps, even 30 amps I would want not to be experimenting with something new....just my conservative nature I guess...

Prevent as many problems as you can and then deal with the ones you missed.....but never twice:-)

Later Ed

[Dave Atherton]

Ed, thanks the electrician stopped by and left his report that Insurance Adjuster requested
for Monday. I guess my knowledge of wiring is very limited and trying to explain something
involved as what goes where. This is what is on the electrician states, wiring caused fire by
power cord connection at junction box ( black strand hot wire ) connection to a # 12 wire
with wire nut. Hot wire from power cord ( strand wire ) came loose from wire nut and fell
down coming in contact and welding to metal junction box that ground wire was connected
to. Junction box was fastened to plywood with wood screws that burned away leaving junction
box hang loose. The # 12 wire has the remaining inside metal wire nut still fasten to the # 12
wire, strand wire from power cord welded to junction box. Electrician said power was off at
R.V power box by fire dept. the power cord was cut loose from motorhome by fire dept.

What I viewed after the fire and tried to explain my lack of understanding about wiring by
looking at the burn't mess of wires. Having a Electrician that works with electricy could pick
out what happened makes a person feel better. Ed, again I do not have any idea about wire
Connectors or wire nuts. Dave