smoke at connection to extension????

[P K]

Hi,
I'm not sure if this is the appropraiate group, but here goes:

I use a electric mower for my small yard. It is about six years old,
has a 12 amp motor and I use a 60' extension with a guage rating that is
one grade above the average orange outdoor cable (can't rmember the
exact number, possibly 12 guage?).

It has overheated and triggered the built-in circuit breaker often
since I bought it. (I just wait 15 minuts and let it cool down)
Today I noticed smoke comming from the connection between the mower
and the extension. One of the male prongs is coated with a black
substance, and the female paart was warm and greasy.

What has caused this and what should I do?
Any help will be appreciated.

Thanks
--Paul

 

[Don Bruder]

Hi,
I'm not sure if this is the appropraiate group, but here goes:

I use a electric mower for my small yard. It is about six years old,
has a 12 amp motor and I use a 60' extension with a guage rating that is
one grade above the average orange outdoor cable (can't rmember the
exact number, possibly 12 guage?).

It has overheated and triggered the built-in circuit breaker often
since I bought it. (I just wait 15 minuts and let it cool down)
Today I noticed smoke comming from the connection between the mower
and the extension. One of the male prongs is coated with a black
substance, and the female paart was warm and greasy.

What has caused this

A cable too small for the distance the juice is being carried. Trying to
run 12 amps on a 60 foot 12 gauge cord is... How to word this
politely... Hmmm... There is no way, so I'll be blunt: STUPID. Resistive
losses in the cord at that length and amperage should, by all rights,
cause your cord (and/or mower) to practically burst into flames on you
within minutes, if not seconds, of turning it on. That you've managed
this long is a small miracle in and of itself.

and what should I do?

Get a heftier cable. Personally, for what you're doing, I wouldn't try
to use anything with conductors smaller than about 8-10 gauge, and
wouldn't hesitate to go even larger if the option were available.

Any help will be appreciated.

You just got the best advice you're likely to find.

 

[P K]

A cable too small for the distance the juice is being carried. Trying to
run 12 amps on a 60 foot 12 gauge cord is... How to word this
politely... Hmmm... There is no way, so I'll be blunt: STUPID. Resistive
losses in the cord at that length and amperage should, by all rights,
cause your cord (and/or mower) to practically burst into flames on you
within minutes, if not seconds, of turning it on. That you've managed
this long is a small miracle in and of itself.

I have used a 16 gauge cable on my older mower. It was recommended to
use a 14 gauge cable with this amp mower. It works fine for my electric
snow blower. My neighbor uses the smaller 16 gauge cable too.

Get a heftier cable. Personally, for what you're doing, I wouldn't try
to use anything with conductors smaller than about 8-10 gauge, and
wouldn't hesitate to go even larger if the option were available.

This sounds like overkill according to the recommendations in the mower's
manual. The bigger cables would be like hauling a garden hose around.

You just got the best advice you're likely to find.

Thanks for your rsponse, I'm just confused now. It worked fine for six
years. And it seemed to be what was apprpriate.
Thanks
--Paul

 

[DaveM]

I have used a 16 gauge cable on my older mower. It was recommended to
use a 14 gauge cable with this amp mower. It works fine for my electric
snow blower. My neighbor uses the smaller 16 gauge cable too.

This sounds like overkill according to the recommendations in the mower's
manual. The bigger cables would be like hauling a garden hose around.

Thanks for your rsponse, I'm just confused now. It worked fine for six
years. And it seemed to be what was apprpriate.
Thanks
--Paul

Wow... what a crock!!! The first answer to the question was uneducated,
and not what the OP needs to hear.
The NEC says that the maximum voltage drop from the source to the last load
on the circuit be 3% or less. A 60 ft, 16 AWG extension cord will drop 7
volts when passing 12 Amps, or a 5.8% voltage drop at 120V. A heavier guage
extension cord is definitely in order, but 8-10 AWG is overkill, and the
last poster suggested.
A 60 ft, 14 AWG extension will drop 4.4V at 12 Amps, or a 3.7% drop.
A 60 ft, 12 AWG extension will drop 2.8V at 12 Amps, or a 2.3% drop, which
is within the NEC guidelines.
The larger the wire, the less voltage will be dropped in the wire, and more
will be available to run the load (the mower). If the voltage at your
receptacle is 120V or more, and if the mower can run well at 115V, then a 14
AWG extension will work, provided you don't use it for extended periods and
allow it to get very hot. Mowing a lawn might be pushing it a bit too much
for safety. I would recommend buying a 12 AWG extension cord for the mower,
and avoid the dangers.
Back to the OP original question, it's quite possible that the receptacle on
the end of the extension wasn't tight, and caused a high-resistance
connection, which overheated the receptacle, causing its demise.

Cheers!!!
--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!

 

[Yukio YANO]

Replace the Male connector from the Mower. The connection between the
mower cable and the male pins (most likely a crimped connection ) has
cooked and now presents a significant IxR drop, plain English, gets
Damned Hot, Less likely it could be the Female Connector on the
Extension Cord. Its' warm and greasy because its cooler than the Male
pin which was hot enough to char the melting plastic break-down products.

Is it overheating and triggering the internal Circuit Breaker because of
low line voltage ? Brown-out ! motor spinning to slowly because of
excessive voltage drop somewhere in the Power Cord/Extension Cord.

12 Gage is fine for the Lenght and Load described, 14 gage is marginal.

Yukio YANO

 

[Warren Weber]

Top posting for OP. John Fields gave you the correct info. The twist lock
male and female are the way to go. Warren

 

[Warren Weber]

Top posting for OP. John Fields gave to the correct solution. The twist lock
is the way to go. I use a 16 gauge 50 foot on my mower, no problem. Warren

 

[P K]

---
If the breaker keeps blowing it sounds to me like youve got either a
faulty breaker, a motor problem, or you're mowing too aggressively and
overloading the motor! I suggest that the first thing you do is check
the motor current while you're mowing in order to rule out the
aggressive mowing, and then if you still have too much current being
drawn, it may be time for a new motor.

I suspect that what happened at the connection between the cords is
that a high resistance developed there, for some reason, and it
overheated, making the condition worse, causing it to heat up even
more...

What I'd do there would be to cut off the plug and socket and replace
them with a new heavy-duty 20 or 30 amp set. you could even get
Twist-Locks so you wouldn't have to worry about the lines unplugging
or having to tie the cords in a knot to keep that from happening.

Great info and advice. The connection had always been loose. I had
to tie the ends together so the motion would not shake them apart.
I have cleaned the prongs and will try the following:
-test it again as is with the connection as tight as i can make it.
-replace connectors with new, tighter, heavy-duty ones.
-replace extension with 12ga
Thanks for all your contributions (ain't this 'net thing great?)
--Paul (OP)

 

[spudnuty]

Yes I agree and have had this exact situation happen with a resistive
connection on my electric mower except it was a little more obvious
because the male end just melted into a gooey blob.
BTW do you use a GFCI to feed your extension cord? I have a little
pigtail that I rigged to a GFCI in a box that I use to power my mower
from all the antique circuits in this building. It has popped a few
times over the years due to little nicks in the cord.

(ain't this 'net thing great?)

It sure is.
Richard

 

[P K]

Yes I agree and have had this exact situation happen with a resistive
connection on my electric mower except it was a little more obvious
because the male end just melted into a gooey blob.
BTW do you use a GFCI to feed your extension cord? I have a little
pigtail that I rigged to a GFCI in a box that I use to power my mower
from all the antique circuits in this building. It has popped a few
times over the years due to little nicks in the cord.
It sure is.

Richard
The outside power boxes on my home are on a GFCI circuit. So that is
not a problem. And my mower has a circuit breaker built in.

To all contributors:
The problem was solved by using a short extension of 12ga wire with
a connector that fits in the mowers plug tightly. The other end fits
to my 60' extension also tightly. Now the mower works without smoke!
(I also sharpened the blades, a good thing for any mower but especially
an electric)
Again thanks to all.
--Paul

 

[spudnuty]

Paul,
As Yukio pointed out that internal breaker in the motor was probably
cutting out because the motor was getting too hot due to to the lowered
voltage. Note that this is a thermal breaker and has been required in
motors for some time I think for fire protection. I've seen them all
the time even in induction types.
Richard

 

[blazeinferno]

Hey Paul,

2 things come to mind:

1) Bad connection...like a loose connection. This
may cause overheating at the connection itself usually possibly melt the
wire or terminal.

2) A motor winding has burnt.

Hope this helps


Fern