I don't want you to make hasty decisions, so I went back on the roof today just for you.
Great. So the phrase of interest is "This ventilator should be installed with remote motor-overload protection when 3 phase or 2HP or larger single phase motors are required."
Does that mean that as the name plate indicates a 1/3 HP single phase motor, remote motor-overload protection is not required because the unit has integral overload protection? If so, seems to me that using a 20A branch circuit OCPD with 20A ampacity conductors, or even with 15A ampacity conductors, complies with Article 430. In which case the only NEC issue I see is whether the unit being labeled MOCP 15A would make that a 110.3(B) violation.
I perused UL 705, the listing standard on the label, and it seems to me that it does not call for the manufacturer to label this unit with MOCP. The labeled FLC is 5.6A, and the labeled MCA is 7A, which is 125% * 5.6A. So there is no room in that computation for another load, the motor must be the only load. While UL 705 says:
36.8 A ventilator having one motor with other loads or more than one motor with or without other loads shall be marked with one of hte following:
a) The minimum circuit size and maximum current rating of the overcurrent-protective device unless both are 15A or less; or
b) The rating of the largest motor in volts and amperes, and the rating of any other loads in volts and either amperes or watts.
Exception: The current value of a motor rated 1/8 horsepower (93W output) or less, or a nonmotor load 1 ampere or less may be omitted unless either load constitutes the principal load.
So assuming all the above is correct, if we conclude that the manufacturer has unnecessarily labeled the unit MOCP 15A, may we ignore that, or is it a 110.3(B) issue?
BTW, the manufacturer seems to have dropped the ball on these provisions of UL 705:
36.5 A ventilator that incorporates motor-overload protection shall be marked to indicate the presence of such protection.
36.6 A ventilator that does not incorporate motor-overload protection shall be marked:
a) To indicate that the ventilator should be installed with remote motor-overload protection; and
b) To provide such motor-rating data--voltage, frequency, horsepower, and full-load current per phase--so that proper protection may be determined.
I.e. if the ventilator has motor-overload protection, as I infer, then the requisite 36.5 marking is missing. Whereas if it doesn't, then the requisite 36.6(a) marking is missing, as the label references that only for 3 phase and 2HP or larger single phase motors, which this unit does not have.
Cheers, Wayne