I'm installing a mast on the gable end of my house on which I'll mount a ham radio antenna:

Antenna Elevation Facing Gable End

The antenna is mounted to 1.5" RMC (the mast) which passes through the eave of the roof. The RMC screws into a surface-mount exterior breaker box. The box contains the antenna discharge unit mounted to a plate on which the bonding lug is also mounted. The insulated (green) bonding conductor runs through a knockout in the bottom of the breaker box and then to the ground rod at the service entrance.

How do I secure the (insulated) bonding conductor in the knockout? Use a metal NM clamp? Use a plastic NM push-in connector? Use a cable gland? I thought about using a Kenny Clamp, but that's not for insulated wire is it? Should I just strip off the insulation where it meets the Kenny Clamp?

Edit: Here's the finished item. You can kind of see the Kenny Clamp: mast

  • Wait, so there's no 120/240V here... they use a NEMA 3R circuit breaker service panel merely for the enclosure, which is designed to take a Rain-Tight Hub and efficiently clamp to the bottom of a mast? Nice trick, I'll have to remember that! Commented Oct 12, 2021 at 0:42
  • Nice trick, I'll have to remember that! I'd love to take credit for it, but it was my wife who came up with idea. :) It turned out pretty well, I think: I removed the breaker fixture, mounted a stainless plate in its place, and mounted the lightning protection and ground lug to that plate.
    – watkipet
    Commented Oct 26, 2021 at 23:12
  • 1
    A) Very strange visual artifact in your picture that make it look like the grounding wire goes through the bottom 3 pieces of siding. B) You've got a smart wife! I'd keep her if I were you! ;)
    – FreeMan
    Commented Jan 21, 2022 at 13:52

2 Answers 2


I'd strip back the bonding conductor insulation then use a Kenny clamp

I'd strip the bonding conductor insulation back enough so that the wire is bare when it passes through the bonding (compression, Kenny) clamp, then simply use one of those to attach the wire to the enclosure. This is fine because dedicated grounding conductors are permitted to be bare.


Take a couple inches of the bonding conductor to your friendly neighborhood electrical supply house*. They will disappear in the back and come back a minute later with your specimen and a perfectly sized strain relief/gland. That's what I do.

* if you think "Imma save some time and go to a big-box store instead", forget it. Their selection is horrid and no one knowledgeable will help you. Also the electrical supply guy would already be back with the right thing before you even cross the parking lot.

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