Should I Run My Tablesaw on 120
or 240 Volts?
My contractor’s saw pops a breaker every once in a while, and that’s
driving me crazy. I noticed that its motor can be wired for either 120 or
240 volts. I don’t have a 240 circuit in my shop yet. Do I have to install one
or is there something else I should try first?
Rewiring your motor and upgrading
the circuit to 240 volts will solve
your breaker problem, improve the
motor’s performance and extend its
working life.However, it won’t increase
the horsepower of your motor.
Before you rewire your motor and
shop make sure your saw is getting as
much power as it can. Don’t run any
other machines or lights on the same
circuit as the saw. If your saw must be
connected to an extension cord, replace
the cord with one that’s shorter and
made with heavier gauge wire.
Finally, see if the amp draw of your
motor exceeds the capacity of your
120-volt circuit.A sound rule of thumb
is that the full-load amps (FLA) of your
motor should be equal to or less than
80 percent of your circuit breaker
rating,or 12 amps for a 15-amp circuit
and 16 amps for a 20-amp circuit. (A
motor’s FLA is written on its nameplate
in a box marked Amps. FLA is
generally two numbers, such as 12/6.
The first number is the amp draw at
120 volts, the second at 240 volts.)
If your motor exceeds this guideline,
and popping your breaker is still a
problem, your best bet is to rewire the
motor to 240 volts. It may only involve
switching a few wires inside the motor
and replacing the plug.Then consult a
licensed electrician about adding a
240-volt circuit to your shop.
This story originally appeared in American Woodworker September 2002, issue #95.