Re: Bonding Bushings (When required)
Alright...I checked into this a bit more, because I had the same feelings as Don. I called a good friend of mine that works for UL, and also happens to serve on CMP 5 (Art. 250, 280, 285). We discussed the listing standard for these fittings. They must pass the same test as a bonding bushing, bonding locknut, bonding wedge, etc., which is the UL 467. The UL 467 contains some various things, but the most relevent info I will post here.
Basically the fittings are tested at the desired voltage (120 and 277 in this case) and subjected to a ground fault of 1,180 amps for 4 seconds of duration for trade size 1/2". For trade size 2", for example, it is the same test, but the duration is only two seconds and the fault current is 3,900 amps. After thinking about it for a while, it is obvious that this test would clear any protective device that could be attached to a conductor that would fit in a 1/2" raceway, and it would clear the fault much, much faster than 4 seconds (probably more like 2 cycles).
