Installing cable with a missing clamp is a common mistake made by DIY electricians. If you see any connections like this in your home or buildings, we suggest you go back and add the clamp to prevent future problems.
The reason is that unsecured cable can cause a strain on the connections. In a metal boxe, the sharp edges might cut into the insulation around the wires and lead arching or a short. Single plastic boxes do not require internal cable clamps, but to keep the wire secure, code requires that the cable be stapled to the stud within 8 inches of the box.
Larger plastic boxes have built-in cable clamps and that cable must be stapled within 12 in. of the box. The metal cable clamps shown in the picture are fine, as are other styles of approved cable clamps.
If you need any help upgrading this type of connection, please give us a call. We’d be glad to come out and make it safe again.