Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Coiled Extension Cord Cause Fire?

Coiled Extension Cord Cause Fire?

Coiled Extension Cord Cause Fire?

Hey all,

A friend of a friend's house burned down last week.  The cause given to them (from who?) is that a coiled extension cord was the root cause.  

Now i^2 r being what it is, I can understand that a cord passing current will heat up - even if not to "overload".  And although I'm a sparky, I can see how not allowing the heat move away from the cord (by coiling it, perhaps) could cause excessive heating resulting in fire.  AND I can even understand (although with a slippery grip) inductive heating of a coiled wire.  But...

Their cord was not connected to a load.  Simply coiled and sitting there - although still plugged into the outlet.

So, what I can't understand is: if there was no load and therefore no current, how could this coil of conductor be the culprit?  I can almost fathom an effect if were were talking about incredibly high frequency (though I'd be reaching way out of my limited intellectual comfort zone).  

Can someone explain what I'm missing, here?

RE: Coiled Extension Cord Cause Fire?

You simply missing the fact that however determined that to be the cause is an idiot and is incorrect.
If there was no load on the cord, there is no voltage/current flow, and no heating..no heat = no chance for fire.  Not to mention that even a fully loaded UL approved/listed cord (loaded to it's max. rated ampacity) does not generate enough heat though its insulation to start a fire.  

RE: Coiled Extension Cord Cause Fire?

I gotta vote with mcgyvr if the facts are as stated.

Even if there were a load, you don't get inductive heating from a coiled cord or they wouldn't sell them to us in lengths longer than a foot or so. The supply and return are in the same cord, there's no net magnetic field.  In this case, with no load at all, there's no current.

Now, if the cord were laying there plugged in, and the cat chewed away the insulation, and the dog dragged his metal water bowl over, and...

Ah, but all the inspectors ever get to see are charred remains.

Good on ya,

Goober Dave

RE: Coiled Extension Cord Cause Fire?

Not to start anything, but given the warnings on the cords package, why would you leave a cord pluged in without anything attached to it?

Most cords that I have seen will say for temperary use only.

So with that in mind, an inspector might believe the cord had to be connected to something. Possibility something to large for the cord.

They really don't know what started the fire. They probally have a good idea of where it started. So they jumped on a conclusion.

RE: Coiled Extension Cord Cause Fire?

This is another wide-spread urban myth.

It is a fact that a coiled extension cord, when carrying current, can overheat. But most have a built-in thermal protection that prevents this from happening. And not loaded will, of course, not overheat.

A warning sign is that it was "A friend of a friend" to which it happened. he "FOF" is a houshold expression in urban myth world.

Gunnar Englund
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Coiled Extension Cord Cause Fire?

Maybe the cord had bad insulation.

Maybe the female plug on the open end was worn out and failed. I have been told before that a well used cord can arc in the female plug, to the point it was caught starting a car cover on fire.

If you have one of the cords in those plastic winders and try to use it for a significant load without unwinding it all you will melt the insulation.

RE: Coiled Extension Cord Cause Fire?

I'd bet on the propane tank anyday...flopping hose leaking propane..hitting metal causing spark..propane igniting... burning down house...
If the fire was already started and enough to burn a hole in the propane line causing a leak, I doubt that the neighbors would hear the hissing of propane without noticing the flames shooting out of it. As soon as that fire burnt a hole in the line the propane would ignite.

RE: Coiled Extension Cord Cause Fire?

Inductive heating at 60Hz from a line cord?  Not likely...

Bad insulation?  Likely...

Dan - Owner

RE: Coiled Extension Cord Cause Fire?

Fused plugs... oh, that's UK-only: everyone else knows better than us. smile

If we learn from our mistakes I'm getting a great education!

RE: Coiled Extension Cord Cause Fire?

Sure, but frayed, or otherwise damaged, cords are quite common.  These things shorting out could certainly start a small fire that gets larger.


FAQ731-376: Eng-Tips.com Forum Policies

RE: Coiled Extension Cord Cause Fire?

An plugged in extension cord will be flagged on any routine fire inspection of a commercial building.  Given that there was a fire, the extension cord melted and then shorted.  That would have given enough evidence to cite the cord.  When they can't find a definite cause it is always easy to say it was electrical.

RE: Coiled Extension Cord Cause Fire?

Let me see, four teenagers home alone.  A gas grill with a disconnected hose. One teenager goes outside to "investigate" an "explosion" that he "thought he heard" and the neighbors saw the propane hose swinging wildly back and forth hissing gas.

Sounds like the fire officials did not do much of an investigation or ask enough questions of the "children".

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close