OT, long boring code dissertation
OK I did some looking.
The first thing you need to define is "Continuous duty motor"
Note: Any motor application shall be considered as continuous duty unless the
nature of the apparatus it drives is such that the motor will not operate
continuously with load under any condition of use.
430.32 Continuous-Duty Motors.
(A) More Than 1 Horsepower. Each continuous-duty motor rated more than 1 hp
shall be protected against overload by one of the means in 430.32(A)(1) through
OK that's a slam dunk
Now how about a non-continuous duty motor
430.33 Intermittent and Similar Duty.
A motor used for a condition of service that is inherently short-time,
intermittent, periodic, or varying duty, as illustrated by Table 430.22(E),
shall be permitted to be protected against overload by the branch-circuit
short-circuit and ground-fault protective device, provided the protective
device rating or setting does not exceed that specified in Table 430.52.
Any motor application shall be considered to be for continuous duty unless the
nature of the apparatus it drives is such that the motor cannot operate
continuously with load under any condition of use.
If a motor is selected for duty-cycle service (short-time, intermittent,
periodic, or varying), it can be assumed that the motor will not operate
continuously, due to the nature of the apparatus or machinery it drives.
Therefore, prolonged overloads are rare unless mechanical failure in the driven
apparatus stalls the motor; in this case, however, the branch-circuit
protective device would open the circuit. The omission of overload protective
devices for such motors is based on the type of duty and not on the time rating
of the motor.
IF the branch circuit O/C device <fuse/breaker> is sized properly for the motor
and the motor can't be locked on (I.E.trigger control with no "lock on" button)
you can do without overload protection. Bear in mind this limits the size of
the motor you can use. If it's too small the typical 15/20a branch circuit O/C
device will not adequately protect the motor. That's why we see thermal fuses
in those cheap fans. This was written, assuming you would size the branch
circuit to a particular motor.
If you have more than one motor on a branch circuit they must have overload
430.53 Several Motors or Loads on One Branch Circuit.
Two or more motors or one or more motors and other loads shall be permitted to
be connected to the same branch circuit under conditions specified in 430.53(D)
and in 430.53(A), (B), or (C).
(A) Not Over 1 Horsepower. Several motors, each not exceeding 1 hp in rating,
shall be permitted on a nominal 120-volt branch circuit protected at not over
20 amperes or a branch circuit of 600 volts, nominal, or less, protected at not
over 15 amperes, if all of the following conditions are met:
(1) The full-load rating of each motor does not exceed 6 amperes.
(2) The rating of the branch-circuit short-circuit and ground-fault
protective device marked on any of the controllers is not exceeded.
(3) Individual overload protection conforms to 430.32.
Two or more motors or one or more motors and other loads may be connected to
the same 120-volt, 15- or 20-ampere, single-phase lighting circuit as long as
each motor is rated not more than 1 hp, the full-load rating of each motor does
not exceed 6 amperes, and the rating of the branch-circuit protective device is
The requirements for overload protection, as provided in 430.32, must be
applied in all cases, regardless of the number (one or more) of motors or the
type of branch circuit.
This brings is to something more relevant to what we use.
430.42 Motors on General-Purpose Branch Circuits.
Overload protection for motors used on general-purpose branch circuits as
permitted in Article 210 shall be provided as specified in 430.42(A), (B), (C),
(A) Not Over 1 Horsepower. One or more motors without individual overload
protection shall be permitted to be connected to a general-purpose branch
circuit only where the installation complies with the limiting conditions
specified in 430.32(B) and (D) and 430.53(A)(1) and (A)(2).
(B) Over 1 Horsepower. Motors of ratings larger than specified in 430.53(A)
shall be permitted to be connected to general-purpose branch circuits only
where each motor is protected by overload protection selected to protect the
motor as specified in 430.32. Both the controller and the motor overload device
shall be approved for group installation with the short-circuit and
ground-fault protective device selected in accordance with 430.53
(C) Cord-and-Plug Connected. Where a motor is connected to a branch circuit by
means of an attachment plug and receptacle and individual overload protection
is omitted as provided in 430.42(A), the rating of the attachment plug and
receptacle shall not exceed 15 amperes at 125 volts or 250 volts. Where
individual overload protection is required as provided in 430.42(B) for a motor
or motor-operated appliance that is attached to the branch circuit through an
attachment plug and receptacle, the overload device shall be an integral part
of the motor or of the appliance. The rating of the attachment plug and
receptacle shall determine the rating of the circuit to which the motor may be
connected, as provided in Article 210.
You see why someone could get confused??
Basically I wouldn't want anything that didn't have some kind of overload
protection unless it was a throw away tool or something you only run
intermittantly with a trigger. Certainly any kind of a free standing tool like
a planer, jointer or table saw that has an on/off switch requires O/L
protection because it is capable of "continuous duty".
IMHO ... and that is how the fist fights begin at the inspector meetings ;-)