I've heard that there is a limited to the distance that a drop cord
for power equipment can be used. Beyond that limit there is risk to
damage the equipment being used. If this is true, what is this
length? My guess is that it depends on the
rating of the drop cord. Is there a source where I can determine
what size cord is safe at what distance?
If you google resistance of copper wire you will
find tables that give the resistance of wire per foot
for each gauge of wire. Then you can use ohms
law to calculate the voltage drop. Let's say the
wire has a resistance of .01 ohms/ft. Then 100
feet would have a resistance of 1 ohm. And if
the load on it is 5 amps, then it will have a voltage
drop of 5 volts. So, if you started out with 120v
at the receptacle, you have only 115V at the end
of the cord.
The rest is up to what the load is, do you really
have 120V at the receptacle, and how lucky
you feel. As a rough guide, you can use the
rule of thumb for residential wiring. 14 gauge for
15 amps, 12 gauge for 20.
I do a bunch of stuff, but no harm yet. Run a 100 foot 12 gauge extension
cord out of garage, but the garage is fed with 85 foot, 10 gauge wire.
Small air conditioner works ok. At camp I ran the air conditioner with 100
foot 14 gauge extension into little trailer from big trailer.
During Xmas I have a 250 foot 18/16 extension to feed small set of lights.
Looks like lights without a house in sight.
The 110 volts at the end of the "drop cord" is only 110 volts if it
is connected directly to the panel - otherwize there is voltage drop
on the 14 g wires from the panel to the outlet as well,. And tha ASS
U ME s you have 120 volts at the panel under load - which is not a
given, as you can have voltage drops between the transformer and the
panel, which will vary depending on the over-all load on the panel at
any given time. - Current voltage on an unloaded branch circuit right
now at my house is 13.9 - 114 VAC with the AC not running. and
113.3-113.5 with the AC on. - 100 amp service 300 feet from the
transformer. About 222 at the AC unit disconnect 50 feet from the
panel on #12 cable.
I have no cite for this, but it has been the rule that I live by for 30
years. For every 100 feet of cord, you are losing 15% of your power. I
only use 12 gauge cords.
I burned up a perfectly good rockwell circular saw by using too much
extension. I had about 215 feet of extension cord out and after 2 hours
of cutting plywood, poof!
Now I never go over 75 feet, but then, I have a generator, so I don't
On Sat, 21 Jul 2012 07:20:51 -0400, "Don Phillipson"
Actually not comeletely true. A too light cord will get hot. A too
LONG cord will develop too much heat too, but not at the connections -
the whole cord will dissipate heat - and because it is spread out over
50 or 100 feet you will not notice it.
For a 15 amp circuit, 80% load, you need a 12 guage cord or better for
100 feet. For 50 a 14 will do the job. For 25 a 16 is common.
No such thing as too heavy for a cord for stationary power tools. For
handheld tools the last couple of feet need to be light and flexible
enough to work with.(so if your saw has a 3 foot whip, you will need a
short lighter cord on the end if you are running a number 12.)
Always choose 1 long enough cord over 2 shorter ones as the connectors
have higher resistance than a few extra feet of cord.
i have a friend who had a heavy motor load in hhis yard on a temporary basis.
so he parelled 3 14 gauge cords for the 20 amp running load.
it worked but i would of installed a proper buried 10 gauge direct burial cable
with GFCI protection. his temporary project took 3 years.....
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.