I am working with a fractional hp motor which has a handy chart in its
install paperwork. I put it on my Web site for general use. It shows wire
sizing to use per horsepower per voltage per length of wire run. For example,
a 2hp motor at 115V at 50 feet should be wired with 4 gauge wire. - GWE

http://www.tinyisland.com/MotorWireSizes.pdf

It's pretty conservative. By this chart a 1/4 hp motor
couldn't be run on the common 15A circuit. And it is
certainly more conservative than other data I have on wire
size, length, and acceptable voltage drop. Perhaps, it is
intended for direct wired motors that are heavy duty and
continuous use.

Grant Erwin wrote:

I am working with a fractional hp motor which has a handy chart in its
install paperwork. I put it on my Web site for general use. It shows wire
sizing to use per horsepower per voltage per length of wire run. For example,
a 2hp motor at 115V at 50 feet should be wired with 4 gauge wire. - GWE

http://www.tinyisland.com/MotorWireSizes.pdf

George, Are you sure you're reading it right?. I haven't connected to
Grant's web site to look at the chart - however *my* chart says a 1/4 hp
motor draws 5.8 amps fully loaded, on a 115 v circuit.

Bob Swinney
"George E. Cawthon" wrote in message
...
It's pretty conservative. By this chart a 1/4 hp motor
couldn't be run on the common 15A circuit. And it is
certainly more conservative than other data I have on wire
size, length, and acceptable voltage drop. Perhaps, it is
intended for direct wired motors that are heavy duty and
continuous use.

Grant Erwin wrote:

I am working with a fractional hp motor which has a handy chart in its
install paperwork. I put it on my Web site for general use. It shows
wire
sizing to use per horsepower per voltage per length of wire run. For
example,
a 2hp motor at 115V at 50 feet should be wired with 4 gauge wire. - GWE

http://www.tinyisland.com/MotorWireSizes.pdf

Yes, his doesn't give amps. It gives wire size and feet for
various motors sizes. It says a 1/4 hp 115V needs 14 gage
for 25 feet, 10 gage for 50 feet, and 8 gage for 100 feet.
15 amp circuits are often 100 feet long and certainly more
than 50 feet and use 14 gage wire.

It says a 1 hp needs 10 gage for 25 feet and 6 gage for 50
feet. My old Craftsman saw with a Sears 1 hp 12.2 amps
motor is built on a movable base that has a 25 foot 16 gage
wire extension wire. Currently, it is plugged into an outlet
that is at least 25 feet from the panel (and probably 14
gage wire). My father used this saw extensively from the
1950's to late 1980s with this same cord and never had motor
problems.

One curiosity. He apparently got the extension cord from
Sears at the same time that he got the saw as the cord is
marked 16/2 300V Motor Cord.

Bob Swinney wrote:

George, Are you sure you're reading it right?. I haven't connected to
Grant's web site to look at the chart - however *my* chart says a 1/4 hp
motor draws 5.8 amps fully loaded, on a 115 v circuit.

Bob Swinney
"George E. Cawthon" wrote in message
...
It's pretty conservative. By this chart a 1/4 hp motor
couldn't be run on the common 15A circuit. And it is
certainly more conservative than other data I have on wire
size, length, and acceptable voltage drop. Perhaps, it is
intended for direct wired motors that are heavy duty and
continuous use.

Grant Erwin wrote:

I am working with a fractional hp motor which has a handy chart in its
install paperwork. I put it on my Web site for general use. It shows
wire
sizing to use per horsepower per voltage per length of wire run. For
example,
a 2hp motor at 115V at 50 feet should be wired with 4 gauge wire. - GWE

http://www.tinyisland.com/MotorWireSizes.pdf

Charts of this type giving motor hp or motor kva instead of amps are usu.
based on the amount of current a motor would "draw" if working fully loaded.
The wire sizes given in such charts are that which will cause a certain
percentage of voltage drop (usu. 2%) over a given length of wire. For
example, a fully loaded 1/4 hp motor would draw about 5.8 amps from a 115 v
single phase circuit. A chart of mine for *110 v* says that 6 amps drawn
from a 110 v circuit would require #14 wire for a 2% v drop over 50 feet.
This goes to #12 wire if the distance is 75 feet and to #10 for 100 feet.

This is very close to the information you mentioned from Grant's chart. So,
Grant's chart is conservative - it may be based on a 1% voltage drop or on
less efficient (imported ?) motors. It may also be "code". There are many
variables that cause recommended wire sizes to vary, but you will never go
wrong if you always stay on the conservative side.

Bob Swinney




"George E. Cawthon" wrote in message
...
Yes, his doesn't give amps. It gives wire size and feet for
various motors sizes. It says a 1/4 hp 115V needs 14 gage
for 25 feet, 10 gage for 50 feet, and 8 gage for 100 feet.
15 amp circuits are often 100 feet long and certainly more
than 50 feet and use 14 gage wire.

It says a 1 hp needs 10 gage for 25 feet and 6 gage for 50
feet. My old Craftsman saw with a Sears 1 hp 12.2 amps
motor is built on a movable base that has a 25 foot 16 gage
wire extension wire. Currently, it is plugged into an outlet
that is at least 25 feet from the panel (and probably 14
gage wire). My father used this saw extensively from the
1950's to late 1980s with this same cord and never had motor
problems.

One curiosity. He apparently got the extension cord from
Sears at the same time that he got the saw as the cord is
marked 16/2 300V Motor Cord.

Bob Swinney wrote:

George, Are you sure you're reading it right?. I haven't connected to
Grant's web site to look at the chart - however *my* chart says a 1/4 hp
motor draws 5.8 amps fully loaded, on a 115 v circuit.

Bob Swinney
"George E. Cawthon" wrote in message
...
It's pretty conservative. By this chart a 1/4 hp motor
couldn't be run on the common 15A circuit. And it is
certainly more conservative than other data I have on wire
size, length, and acceptable voltage drop. Perhaps, it is
intended for direct wired motors that are heavy duty and
continuous use.

Grant Erwin wrote:

I am working with a fractional hp motor which has a handy chart in
its
install paperwork. I put it on my Web site for general use. It shows
wire
sizing to use per horsepower per voltage per length of wire run. For
example,
a 2hp motor at 115V at 50 feet should be wired with 4 gauge wire. -
GWE

http://www.tinyisland.com/MotorWireSizes.pdf

Bob Swinney wrote:

Charts of this type giving motor hp or motor kva instead of amps are usu.
based on the amount of current a motor would "draw" if working fully loaded.

Perhaps Grant's chart is based on starting current which is typically
quite a bit higher than run current, even at full load. While to brief
in proper operation to overheat the wires, I have seen a case where a
small generator could keep an appliance running but couldn't start it.

Ted