I just recently bought a box of the Raco 4714 "Insider" inside-the-box connectors for the first time. I think these have been around for a while, but I canít say that Iíve ever used them before. These are neat for old work, like fishing a wire into a box or panel thatís flush mounted in a finished wall. They have a pretty good range of wire combinations and I particularly like that they are almost perfectly flush with the inside of the box when installed, so they donít take up any additional space when used with something like an octagonal box. Seems that Hubbell currently only makes them for 1/2" K.Oís., but it would be great if they could also offer them in 3/4" and 1" to handle 8/3 and 6/3 NM. I know Rack-a-tiers has made a similar type of 1/2" NM cable connector for years, but I donít really like how far theirs protrude when installed from inside the box.
One thing that caught my attention was where they say that these are the only NM cable connector listed for use in eccentric knockoutsÖ. What? I have to admit that is not something that ever even crossed my mind before when using any NM cable connector. I always thought that the eccentric/concentric KO concern was about grounding and bonding with metal raceways, especially for service equipment or for over 250V.
So this got me to thinking, which is never a good thing, about MC or AC and FMC type connectors used with eccentric KOís. Looking at MC connectors in the 2011 White book, it says they are considered suitable for grounding in circuits over and 250V, when installed in accordance with the NEC. So hopefully that means they are suitable for use with both concentric and eccentric KOís as is, without the need for bonding bushings or grounding locknuts, even for circuits over 250V.
METAL-CLAD CABLE CONNECTORS, TYPE MC (PJOX) GENERAL
Grounding ó Metal-clad cable connectors for use with metal-clad interlocking armor ground cable, corrugated aluminum or copper tube, or smooth aluminum tube, are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with ANSI/NFPA 70, ĎĎNational Electrical Code.íí
I still have some of them from when I was in business. I think Raco is playing smart by getting them listed for eccentric knockouts, as KJay says, most of us probably don't even give eccentric KO's a thought when it comes to NM connectors.