Unfortunately and contrary to popular belief by IEC manufacturers, NEMA/UL Type 1 exceeds the requirements of IP20, but it does not reciprocate. IP 20 includes a foreign object insertion test saying that any device more that 12.5mm cannot enter the enclosure, which is roughly 1/2 inch. But NEMA/UL requires what is called a "rod entry" test where a 1/8 inch diameter (3.2mm) rod is used for testing if any of the live internal parts are within 4 inches of the enclosure edge, 1/2 inch only if the live part is over 4 inches away. So as I said, anything labeled NEMA/UL Type 1 will be equivalent to IP 20 because obviously if a 1/8" rod cannot get in, a 1/2" rod cannot. But an IP 20 enclosure can only meet NEMA/UL Type 1 if the live terminals inside are more than 4" away from the enclosure wall.
When you buy a stand-alone enclosure, somewhere there is an instruction sheet telling you this. In the case of Hoffman and the like, the back panel edge is already 2" away from the wall, so they tell you not to mount any live terminal within 2" of the edge (most people have never seen this, but never violate it anyway). However when you buy an enclosed piece of equipment, such as a VFD, it generally must be UL listed to be used here. When the VFD manufacturer goes to get it UL listed, they must pass that rod entry test. So if any live parts are within 4", the IP20 rating it got under IEC rules becomes meaningless. That is why you often see smaller IEC designed VFDs require an "entry box" accessory that looks like a cheap little can bolted on as an afterthought... because it is. So without that can, these smaller VFDs will only be UL listed as an "open" controller, meaning that here in the US, you must either put it in a box or find that accessory box.
And yes, I'm aware that most readers will have been totally unaware of this and may have, not knowing, mounted and wired small IP 20 VFDs and other IEC devices in violation. In addition, many electrical inspectors are unaware of this as well and so may have approved them; what's done is done. The people who know better are the people who submitted their products to UL for listing, and found out in the process (that's how I learned it). Some of the "less that forthright" vendors allow their customers to believe that their IP 20 devices are OK to mount and wire here in North America, even though they know the issues, but it might interfere with their low-ball pricing strategy so they bury the details deeply or obscurely in an instruction sheet somewhere strictly as a CYA move to avoid the legal costs when something goes wrong.
My understanding of the NEMA standard is that for a ventilated enclosure with parts less then 4" from the opening a 1/2" rod is used, the 1/8" rod test is for non-ventilated enclosures. Has this changed?
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