extension cord on a reel

[John Shamblin]

I have a 50 ft. 3 wire extension cord for use with an electrical leaf blower
or weed eater outside. I normally keep the cord wound around a plastic reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because of
the inductance (and impedance of the 60 Hz current flowing through it) when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John

 

[John Larkin]

On Sun, 31 Oct 2004 11:54:09 -0600, "John Shamblin"
<jshamatcomcast.net> wrote:

I have a 50 ft. 3 wire extension cord for use with an electrical leaf blower
or weed eater outside. I normally keep the cord wound around a plastic reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because of
the inductance (and impedance of the 60 Hz current flowing through it) when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John

The inductance will be the same, wound or not. They're probably
concerned with cooling.

John

 

[Rich Grise]

On Sun, 31 Oct 2004 11:54:09 -0600, John Shamblin wrote:

I have a 50 ft. 3 wire extension cord for use with an electrical leaf
blower or weed eater outside. I normally keep the cord wound around a
plastic reel whose inside diameter is 6 inches and there are about 50
turns of the cord on the reel when full. A caution on the side of the
reel states the "cord should be removed from the reel before use". I
assumed that was because of the inductance (and impedance of the 60 Hz
current flowing through it) when wound on the reel would impede the
current flow in such a coil. Is this truly significant or are there
safety factors to be considered? John

It's probably a cheap cord, and it needs to be exposed to air along
its whole length, or it will overheat from I^2*R losses.

The amount of inductance in a coil like that at 60 Hz is negligible,
and it's a bifilar winding, wired parallel opposing, so will cancel
out anyway. Boy, that really sounds like I know what I'm talking about,
doesn't it? ;-)

Cheers!
Rich

 

[Joe]

A buddy of mine had one of these extension cords powering a window air
conditioner while coiled up. By the end of the summer the plastic
reel had melted to the carpet.


On Sun, 31 Oct 2004 11:54:09 -0600, "John Shamblin"
<jshamatcomcast.net> wrote:

I have a 50 ft. 3 wire extension cord for use with an electrical leaf blower
or weed eater outside. I normally keep the cord wound around a plastic reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because of
the inductance (and impedance of the 60 Hz current flowing through it) when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John

 

[Michael Black]

Joe (joe@emailserver.net) writes:

A buddy of mine had one of these extension cords powering a window air
conditioner while coiled up. By the end of the summer the plastic
reel had melted to the carpet.

But the issue isn't first that it was rolled up. One doesn't want to

use an extension cord without very careful consideration with something that
uses power like an air conditioner. And the fact that he had at least
some of the cord rolled up means that it was a lousy choice, since he
could have used a much shorter extension cord.

Michael

On Sun, 31 Oct 2004 11:54:09 -0600, "John Shamblin"
jshamatcomcast.net> wrote:

I have a 50 ft. 3 wire extension cord for use with an electrical leaf blower
or weed eater outside. I normally keep the cord wound around a plastic reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because of
the inductance (and impedance of the 60 Hz current flowing through it) when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John

 

[Gareth]

John Shamblin wrote:

I have a 50 ft. 3 wire extension cord for use with an electrical leaf blower
or weed eater outside. I normally keep the cord wound around a plastic reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because of
the inductance (and impedance of the 60 Hz current flowing through it) when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John


Another factor could be heat dissipation.

The cable will have some small, but non zero, resistance. This will
cause some of the electrical power to be converted to heat in the cable.
If the cable is coiled up the heat cannot escape as easily as if the
cable were uncoiled. Therefore the temperature rise in the coiled cable
will be higher for the same current flow. The coiled cable could
therefore overheat and catch fire even though the current was less than
the rated current for an uncoiled cable.

Gareth.

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[Don Kelly]

"John Shamblin" <jshamatcomcast.net> wrote in message
news:98KdnWJnkYVVuxjcRVn-jQ@comcast.com...

I have a 50 ft. 3 wire extension cord for use with an electrical leaf
blower
or weed eater outside. I normally keep the cord wound around a plastic
reel
whose inside diameter is 6 inches and there are about 50 turns of the cord
on the reel when full. A caution on the side of the reel states the "cord
should be removed from the reel before use". I assumed that was because
of
the inductance (and impedance of the 60 Hz current flowing through it)
when
wound on the reel would impede the current flow in such a coil. Is this
truly significant or are there safety factors to be considered?
John

----

Overheating- the extension cord is (thermally) rated on the basis that it is
extended and not enclosed. For example, codes would not allow the use of
extension cords in a wall in place of proper wiring. The reel is handy but,
in my mind, its usefulness for storage and winding is outweighed by the fact
that one should completely unwind the cord when using it.
As Rich has said, it's not the inductance. If your blower is like mine, you
should really have a cord rated at 12A (unwound).

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer