Okay, let's break down the issues with the MC cable installation you described.

Regarding the MC Cable Fitting



Likely Incorrect

Without seeing a picture of the specific fitting and the application, it's impossible to say definitively why it's wrong. However, you mentioned you think it's the wrong fitting, so I can assume you are more familiar with the installation than I am. Most MC cable fittings are designed to properly mate with either a box knockout (using locknuts) or to screw directly into a threaded hub. Key considerations:

Type of Box

Is the fitting designed for the type of electrical box being used? (e.g., metal vs. plastic, knockout size)

Cable Size

Is the fitting properly sized for the diameter of the MC cable? A loose fit can compromise the grounding path and allow the cable to pull out.

Purpose

Is the fitting listed and intended for MC cable? There are fittings that look similar but are designed for other types of conduit or cable. Using the wrong one can violate code.

Environmental Rating

If this is an outdoor or wet location, is the fitting rated for that environment?

Anti-Short Bushing

Is an anti-short bushing present inside the cable to protect the wires from sharp edges of the cable armor?

Regarding Supporting and Securing MC Cable



Code Compliance vs. Best Practice

You are correct that the NEC (National Electrical Code) does allow for supporting MC cable by laying it across framing members in certain situations. Specifically, you can usually support it by following the distances outlined in the applicable code (usually a specific distance from boxes and then at intervals, like every 6 feet horizontally).

Damage Potential is the Key

This is where your concern is very valid. Code compliance is the minimum requirement. Even if it's technically permissible to lay the MC cable across the framing, your assessment of the likelihood of damage is critical. Factors to consider:

Traffic

Is this area likely to see foot traffic, storage of materials, or other activities that could put stress on the cable?

Sharp Edges

Are there any sharp edges on the framing members that could abrade the cable over time?

Sagging

Over long spans, the cable may sag, increasing the risk of damage if something is placed on top of it.

Insulation and Other Trades

Future insulation work, plumbing, or other trades could easily damage a poorly supported cable.

My Thoughts on the Installation

Based on your description, here's my overall assessment:1.

Incorrect Fitting

If you have reason to believe the fitting is not the correct one, replace it with a properly sized and listed fitting for MC cable, ensuring it matches the box type and environmental conditions. This is a safety issue and could lead to grounding problems or cable pull-out.2.

Support/Securing

Even if laying the cable across the framing members is technically allowed by code, it seems like a poor installation. I recommend adding appropriate cable supports (e.g., straps, staples designed for MC cable, J-hooks) to secure the cable to the framing. This will: Reduce the risk of physical damage. Provide a more professional and reliable installation. Potentially prevent issues during inspections.3.

Consider Sleeving

If the cable must cross a high-traffic area or a potentially abrasive surface, consider sleeving it with conduit (e.g., PVC) for added protection.

In Summary: Don't just meet the bare minimum code requirements. Strive for a robust and safe installation. Your concern about the potential for damage is valid. It's better to err on the side of caution and provide adequate support and protection for the MC cable. Address the fitting issue immediately. The correct fitting is crucial for safety and proper grounding.Always consult the NEC and local codes for specific requirements in your area. If you are unsure about any aspect of the installation, consult with a qualified electrician. Flag for review