1500-watt extended heater cord is hot.

I use twice the cord of the same type for twice the distance for
a Sears portable 1500-watt heater. The problem is that the
cord is hot to the touch when we use it for a hour or more. But
the cord is not hot if I use a normal distance cord design for the
heater. How do I extend the heater cord twice the distance
without getting the cord hot?

TIA,

 

The cause of many a fire and death.

Use much larger cord. Continuous duty (over 3 hours) derate the
cable to 80% of normal. Personally, I *never* use anything smaller
than 10AWG cable for electric heat. Considering the life-safety
implications the added cost falls away to meaninglessness (in
my world, anyway.) If you're running hundreds of feet, 10AWG might
not be adequate either.

 

So you've now moved from trying to put two coils on your car or
jump-start it with a welder, to trying to burn your house down by
improper use of extension cords with electric heaters...

Dude, you're a disaster looking for a place to happen. There's only
possible thing to say about you: You're fucking NUTS! I take that
back... maybe there are two things: You're a troll, and a particularly
inept one.

Investigation/exploration/experimentation is one thing, but the crap
you're pulling outta your ass is neither. It's sheer stupid in action,
and quite likely to get somebody killed. I'll look for you on the Darwin
Awards. Hopefully, your award will come soon, before you kill an
innocent bystander with yet another of your half-baked, hare-brinaed
ideas.

 

An extension cord for a heater is 'half-baked, hare brinaed'? Thats harsh.

Its something that alot of folks would try to do. The fact that he is asking
is a good sign, and allows the folks who really understand this stuff (not
me, unfortunately) to weigh in.

I'm a bit confused by this too. If you double the length of your wire, you
double the resistance (since R = rho * length/cross sectional area). Since
rho is fixed for copper at 10.4, and the area for a given mil (probably #16)
is fixed, R is proportional to length.

Because of this, and the fact that power dissipated by a wire is I^2R, the
power dissipated is proportional to the length.

I would guess that the ability of a wire to dissipate heat is also dependent
on the length, since its almost certainly proportional to the surface area
of the wire. However, this is where I'm probably wrong. Its probably the
case that much of the heat is dissipated by connections to the ends, and
consequently, while heat generation is constant along the length of the
cord, the heat dissipation is non-linear wrt length...

However, without proper knoweledge of the mechanisms behind heat dissipation
in power cords, I would simply rely on a pre-built cord that was designed to
handle 1500W. The following article has some interesting facts.

http://www.cpsc.gov/cpscpub/pubs/16.html

Here is a fairly cheap cord that will work properly, I think:

<http://tools.mainseek.com/333R16P789K9-Coleman-Cable-02509-100'-12/3-SJTW-O
range-Extension-Cord.html>

Regards,
Bob Monsen

 

Harsh? Perhaps. If so, it's no more harsh than the likely results of the
screwball ideas that this accident-looking-for-a-place-to-happen has
been floating in the past few weeks, under the guise of "investigating"
and "experimenting". So yes, "half-baked and hare-brained" (and do
please pardon my transposed "n" and "a" in the first posting) seems
quite appropriate to me.

 

Oh, I thought it was dialect... sounded Scottish...

I'm guessing that a large number of the floor heaters sold in the US are
used with improper extension cords, probably old lamp extensions. Its
totally unsafe, and causes fires. Therefore, posting some information
regarding this makes perfect sense.

Also, the basics newsgroup is for these kinds of questions. You don't want
to scare off newbies.

Flaming responses such as yours should be reserved for important political
or gun control discussions on sci.electronics.design.

Regards,
Bob Monsen

 

Hey...If you drive a Ford you will try anything to get it
started in cold weather.

 

Tibur Waltson wrote;
"I use twice the cord of the same type for twice the distance for a
Sears portable 1500-watt heater. The problem is that the cord is hot to
the touch when we use it for a hour or more. But the cord is not hot if
I use a normal distance cord design for the heater. How do I extend the
heater cord twice the distance without getting the cord hot?"
____________________________________
Re;
Not much info Tibur... What size is the cord? You know; the "gauge
number"? It is doubtful that the extension you are using is of the same
size/material (same size conductor) if the cord temperatures are
appreciably different. It sounds like you're using a #16 or #14 cord.
The #16 would have a dissipation of about 1.3W/ft of twin conductor
cord, making it quite warm (especially if coiled or covered by a rug or
such); the #14 would have about 0.8W/ft. To be safe, I wouldn't use
anything smaller than a #12 extension; the suggestion of #10 is even
better.
Having said that, I was under the impression that most, if not all,
portable heater manufacturers advise against the use of "extension"
cords for their heaters in the owners manual.

-Dan Akers

 

Well I live in Edmonton Alberta. The low tonite is forcast at
-35C . I have a block heater and charger on the battery.

My extention corn runs from the back of the house out across
the sidewalk. I felt the cord.

Nothing feels warm at all. Can I say " Cold as a witches tit".

 

I meant to say cord.. It's hard to type with frostbitten fingers.

 

Sure..Five stores in Edmonton.

 

Hmmm... please wait...I will go take a look again...

My goodness, I'd been using a #18 extension cord
designed for a 1200-watt heater. The problem is
solved, thanks to all. I had the wrong impression that
#18 AWG/2 is better than #16 . I didn't want to ask
for a while because it sounds sooo "hare-brained."

The original cord that doesn't heat reads 16 AWG/2
90-degrees C. I have no idea what AWG/2 stands for.
From now on I will use #10 cords.

sci.electronics.basics serves more than
straighten things out - it SAVES LIVES. Thanks!

Tibur

 

AWG is American Wire Gauge. The /2 means two wires.