Butterfly Clamp Orientation

[RSquirrel]

I am replacing a ‘70’s Zinsco breaker panel with Square-D. Whoever originally installed the panel, used “butterfly” cable clamps (see attachment) at the top knockouts, and oriented them such that the clamp “wings” are inside the panel and the screws are outside (above) the panel with the screw-heads pointed toward the back of the panel. This suggests that the clamps were “tilted” into place from above the panel, and tightened from the back of the panel, before the sheet-rock was in place.

For the replacement panel, I would like to orient the new butterfly clamps with their wings outside (above) the panel and the screws inside the panel, with the screw-heads pointed toward the front of the panel (i.e. accessible from the open front of the panel). Other than comments stating that both methods have been used, I was unable to find anything on the web or in the 2008 NEC that prohibits this installation method. The knockouts are well forward of the back of the box, so bottoming of screws would not be an issue. See the attachment for a comparison between the two methods.

Q1. Does my proposed method violate any NEC articles?

Q2. What (if any) are the negatives for my proposed method?

 

[tom baker]

Nice drawing. I have never used that type of clamp, what does the catalog/instructions say?

 

[drcampbell]

My guess is that either's fine. The cable is prevented from moving around and protected from the sharp edge of the hole.

 

[ptonsparky]

We used them both ways and if I had a local stocking distributor would be using them more often.

 

[RSquirrel]

tom baker - Thanks, I do a lot in AutCAD. Even on the Halex website there are no instructions and I have been unable to find any instructions elsewhere.

drcampbell and ptonsparky - Thanks, I will proceed with confidence. My local Home Depot sells them (at least one of the sizes).

 

[Little Bill]

Why not just use the "pop-in" NM connectors? Just push them in and insert the cable.
I don't recognize the clamps mentioned in the OP, anyone have a link? I'm thinking they are just NM squeeze connectors.

 

[RSquirrel]

Because I have 12 NM cables of various ampacities and only 5 knockouts to run them through (so some clamps have to accept 2 or 3 cables). I believe the pop-in ones you cite only accept one cable. Google Halex 26510 through 26515.

 

[pjones]

I was told that it was ok to install it either way, by a retired electrical inspector. I haven’t had a need to confirm that in any way therefore I’ve never looked any further into it so take that for what it’s worth, I’m just some dude on the internet.


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[LarryFine]

Why not just use the "pop-in" NM connectors? Just push them in and insert the cable.
I don't recognize the clamps mentioned in the OP, anyone have a link? I'm thinking they are just NM squeeze connectors.

Tomic connectors:

 

[Little Bill]

I hate those!

 

[hbiss]

Because I have 12 NM cables of various ampacities and only 5 knockouts to run them through (so some clamps have to accept 2 or 3 cables). I believe the pop-in ones you cite only accept one cable. Google Halex 26510 through 26515.

I'm not seeing where they are listed for any more than one cable.

-Hal

 

[oldsparky52]

I hate those!

That's funny, I loved them when I did residential in the early 70's. No locknut to mess with.

 

[Frank DuVal]

Arlington says two cables for the black plastic snap in connectors. I've never been cited by the AHJ for doing it.

Ah yes, Tomic connectors, seen thousands in this area, used them both inside and outside the box for old work where you cannot get a screwdriver to the outside of the panel box. Common on SEU cable too!