HVAC OCPD is oversized by 5 amps from the manufacturer's plate.

[wwhitney]

I see this marking guide as well as the label as both being 110.3(B) listing and labeling instructions.

Thanks for the excerpt from the Marking Guide. This prompted me to take another look at UL 1995, as well as dig up an older version (1999) available as a PDF. I think I have a handle on the issue now:

The older version had an Equipment Marking clause as I originally expected to find, one which refers you to another Clause for the significance of the choice. [Then Section 36 is now Section 44]:

36.3(i) for each hazardous voltage circuit which powers more than one motor or a motor and other loads rated 1.0 A. or more as shown in Figure 36.2 (see Clause 36.15) "MAX. FUSE______", or "MAX. CKT. BKR.______ (HACR type per NEC)" or equivalent. See Clause 36.17 for requirements when other wording is used.

Clause 36.17 provides additional requirements related to short circuit testing if the nameplate says anything other than "Max Fuse." But that clause, and the reference to it, has been deleted in the current version of UL 1995. [36.15 / 44.15 just tell you how to calculate the value of MOCP.]

Instead, the current UL 1995 has an additional subsection of Clause 44.3 related to short-circuit current:

44.3( y) The short-circuit current rating of the motor controllers, equipment control panel, overall equipment panel, or industrial control panel when employed with multimotor and combination-load equipment.

Exception: Equipment intended for use in one- and two-family dwellings, cord-and-attachment-plug connected equipment, or equipment supplied from a branch circuit protected at 60A or less is not required to be marked with a short-circuit current rating.

And then Clauses 44.20 through 44.27 elaborate on the marking required by 44.3( y). In particular, 44.24 says:

44.24 A short-circuit current rating for a motor controller, an overload relay or a combination motor controller, as specified in items (a) or (b) of Clause 44.23, shall only be used as the short-circuit current rating of the component when the specified branch circuit protective device is provided.
[Exceptions which allow substitution of one fuse for another, or one current limiting circuit breaker for another, if the "peak let-through current and I²t" is not larger than the specified one.]

My take away, as the UL Marking Guide suggests, is that if the nameplate says "Max Fuse," and you use a circuit breaker instead, the marked SCCR on the unit no longer applies.

However, if this is the only reference to the type of the "specified branch circuit protective device" in UL 1995, that does suggest that such a substitution is of no significance when installations are not subject to any SCCR requirements, e.g. in situations listed in the exception to 44.3( y) where the nameplate is not even required to show an SCCR.

If that is correct, then the UL Marking Guide could use updating. As always, it is possible I have overlooked some other requirement somewhere else in UL 1995, as the free online access does not allow searching. I have, at least, reviewed all of Section 44 on Equipment Marking, from which any such requirement really should have a reference.

Cheers, Wayne

 

[Flicker Index]

Also read the nameplate carefully. Some minisplits we see call for "Fuse protection" as opposed to fuse or breaker. If the name plate only mentions fuse the protection must be by a fuse at the panel or disconnect.

That could be for motor drive hardware protection from occurrences such as gate latch-ups.
https://www.stateelectric.com/products/bussmann-dfj-20

AC equipment can have higher OCPD, because things are not plugged into it and overload protection is provided by the compressor overload. So the breaker at panel serves as a short circuit protection.