Appliances with a two wire cord is allowed by listing of that appliance, that is not on us as installers one bit.
As installers we can't install non grounding receptacles as a general rule, but do have some exceptions for dealing with replacing an existing non grounding receptacle. Seems more logical to me to install a grounding receptacle without an actual EGC and to GFCI protect it then to encourage users to break off grounding pins on the cord. Sure you haven't really changed anything if there is no EGC present, but if they move that appliance to another location that does have an EGC present that broken off pin on their cord doesn't do anything at the new location.
again, the logic is not adding up. the appliance is designed with egc pin and gets listing approval that way, which in my mind tells me it is designed to be used with a grounded nema5 (US 120v), but now you say NEC creates an exception to get around design and listings so that people stop breaking off their egc pin on cords? this logic is just making sense to me.
ok, now let me ask, has there been a boat load of incidents of a 3pin cord having its egc pin broken off and used as-is and something happens, shock, fire, xyz ???
with the NEC verbiage written as-is the exception almost contradicts the requirements that all new wiring use 2CCC+egc. If a 2wire nema5 is absolutely safe w/o egc (must be gfi protected) and you allow 3pin plugs to use that, then why is a new home that is all 2wire (gfi protected) not acceptable?
all this talk about hazards. i can name many hazards that NEC does not address, but the same 'ol argument comes back, "
well, it doesnt really happen that often so they dont address it".
lets take the new hazard created by allowing nema5 on 2wire ckt. the panel is a spaghetti mess, Joe the electrician comes in and replaces a nema1 with nema5 recept and replaces ocpd with a gfi one. 2yrs later the outlet keeps failing so Larry the neighbor comes and sees a nema5, he finds the breaker in the panel but the breaker keeps tripping, after some testing he determines the breaker is faulty and gives the owner two options, replace with a new gfi breaker or a std breaker because the gfi is more expensive. owner says go with the less expensive item. the potential hazard is now real because Larry didnt realize the nema5 was a 2wire only, all those fancy stickys fell off 1.5yrs prior, all he saw was a black wire attaching to a breaker. certainly wasnt the right way to diagnose or assess the issue, but Larry is not an electrician.
so in essence, if the NEC code writers are writing to prevent not-that-often "potential hazards" then they better stop writing the words as if such words are only read by certified/licensed electricians. most locales allow owner to do their own work, etc.
from my view, 2wire ckts should stay on nema1's an ocpd's should be gfi versions, or if supported a 3wire gfi recept installed to feed the nema1's.
cheers. enjoy fixing that "potential hazard" that comes from breaking off egc pins.