I am running 250-250-250-3/0 SER from an outside disconnect to an indoor breaker panel and want to make sure I am properly securing the cable where it enters each box. The problem that I am running into is that the common sizes of clamps (like the one in the link below) are too small. What is my best option?


  • Any reason you can't do conduit? NM clamps are basically only available up to 2 inch, but conduit is easy to source in 3 inch, which will easy hold cable that size.
    – KMJ
    Oct 27, 2023 at 20:51
  • You're limited by your suppliers. Letting the TV set tell you where to exclusively shop, in electrical, is like tying one hand behind your back. Get to know a friendly neighborhood electrical supply. Oct 28, 2023 at 20:38

1 Answer 1


That's because that clamp is designed for flat-ish cables

Your problem is that you're looking at a clamp designed for flat-ish (SEU) cables. For the SER cable you're using, you need something designed for round cables instead -- you should have no trouble getting your cable to fit into an Arlington 849S fitting, for instance.

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