Rule 28-308 Overload Protection Not Required
Overload protection shall not be required for motors complying with any of the following:
(a) A manually started motor rated at 1 hp or less that is continuously attended while in operation, which is on a branch circuit having overcurrent protection rated or set at not more than 15 A or on an individual branch circuit having overcurrent protection as required by Table 29 if it may be readily determined from the starting location that the motor is running; or
(b) A motor constructed so that it cannot be overloaded; or
(c) A motor whose operating requirements are such that it is impracticable to obtain proper overload protection; or
(d) An automatically started motor having a rating of 1 hp or less forming part of an assembly equipped with other safety controls that protect the motor from damage due to stalled-rotor current and on which a nameplate, so located as to be visible after installation, indicates that such protection features are provided.
Rationale and Intent for Rule 28-308.
Some motors are built that cannot be overloaded, some cannot be protected because of the type of load or duty, and some form part of an assembly that satisfactorily protects the motor. We intend not to require an overload device where it is not needed because of motor construction, operating requirements, or when the motor has a rating of 1 hp or less and is part of an assembly that satisfactorily protects it.
Rule 28-602(3) & Table 45
3/4-hp 230-volt motor draws 6.9-amps . .
A disconnecting means for a motor, motor starter, or controller shall comply with Subrule (1), except that:
(a) An isolating switch or a general-use switch used as an isolating switch, if lockable in the open position, marked as required by Rule 26-100(2) and having a current rating not less than 115% of the full load current rating of the motor it serves shall be permitted to serve as the disconnecting means for a motor or motor starter:
(i) Rated at more than 100 hp if for 3-phase operation; or
(ii) Rated at more than 50 hp if for other than 3-phase operation; and
(b) A manually operated across-the-line type of motor starter shall be permitted to serve as both starter and disconnecting means for:
(i) A single motor providing it has a horsepower rating not less than the single motor it serves; or
(ii) A group of motors providing it has a horsepower rating not less than the largest motor in the group and a current rating not less than 115% of the full load current of the largest motor in the group plus the sum of the full load currents of all the other motors in the group which may be in operation at the same time; and
(c) An attachment plug shall be permitted to serve as a disconnecting means for a portable motor and its starting and control equipment provided:
(i) The attachment plug and receptacle has a current rating not less than the ampacity of the minimum size conductors permitted for the motor branch circuit or tap in which they are connected and are used only as an isolating means and not to interrupt current; or
(ii)
The attachment plug and receptacle is used as permitted by Rule 28-500(3); and
(d) The draw-out feature of a high-voltage starter or controller of the draw-out type shall be permitted to serve as the disconnecting means for the motor or controller providing it is used only as an isolating means and is not used to interrupt current; and
(e) A manually operated general-use ac switch complying with the requirements of Rule 14-510 having a current rating not less than 125% of the full load current of the motor and which need not be horsepower rated shall be permitted to be used as a disconnecting means for a single phase motor; and
(f) A fused or unfused motor circuit switch shall be permitted to be used as a disconnecting means for a group of motors served from a single circuit and need not have a rating greater than that necessary to accommodate the proper rating of fuse required for the fused switch provided it has:
(i) A horsepower rating not less than that of the largest motor in the group; and
(ii) A current rating not less than 115% of the full load current of the largest motor in the group plus the sum of the full load currents of all the other motors in the group which may be in operation at the same time.
Tony Moscioni
Electrical Inspector
Electrical Safety Authority
