You're right to question that and to want to look into the NEC. Using 1" one-hole straps screwed directly into the panel to secure wires is generally not permitted by the NEC and considered a code violation for several reasons.Here's a breakdown of why and where to look in the NEC

Why It's a Problem (Code Violation):
Compromised Panel Integrity

Screwing into the panel's enclosure weakens it and can compromise its listing. The panel's enclosure is designed to contain arcs and faults. Holes can provide a path for these to escape.

Sharp Edges and Insulation Damage

Sheet metal edges are often sharp. Screwing straps directly against the metal can damage wire insulation over time due to vibration and abrasion. This leads to short circuits or ground faults.

Not Designed for the Purpose

One-hole straps are typically not designed to be the sole means of securing conductors inside an enclosure, especially in a service panel. They lack proper insulation and protection.

Panel Listing Requirements

Electrical panels are Listed and labeled by testing labs. Any modifications to the panel voids the listing.

Relevant NEC Sections (Start Here)



NEC 110.3(B) Examination, Identification, Installation, and Use of Equipment

Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling. This is HUGE. The panel is a listed piece of equipment. The instructions that come with the panel will never tell you to screw directly into it to support conductors.

NEC 312.5 Cabinets, Cutout Boxes, and Meter Socket Enclosures. Conductors Entering Boxes, Cabinets, and Fittings

This section covers how conductors must enter enclosures, including cabinets and panels. While it doesn't explicitly forbid straps, it mandates methods that don't damage the conductors or compromise the enclosure's integrity. It specifies where to support the conductors on the exterior of the box.

NEC 314.17(C) (1) and (2) Support. Nonmetallic Boxes

Supports for cables is required within 12" of the box.

NEC 314.17(C) (3) Support. Metal Boxes

Supports for cables is required within 12" of the box.

What IS Permitted (Typical/Acceptable Methods)



Cable Ties (Ty Wraps)

Cable ties are the most common and generally accepted method for securing wires inside a panel. Use appropriately sized and rated cable ties.

Cable Clamps

Cable clamps are designed to secure cables entering the enclosure.*

Adhesive-Backed Tie Mounts

These can be used in some situations to provide anchor points for cable ties, but ensure they are rated for the environment and application.

In Summary:

Screwing 1" one-hole straps directly into a panel to secure wires is almost certainly a code violation. It compromises the panel's integrity, can damage wires, and isn't an approved method. Use cable ties or other appropriate methods. Flag for review