You are correct. The situation you describe, where aluminum RMC passes through a slab and is later sealed with fire-stopping material, is not considered "encased in concrete" as the term is typically understood in the NEC and in interpretations of local amendments like NYC's.Here's a breakdown of why: Meaning of "Encased in Concrete"

The term "encased in concrete" generally implies the conduit is embedded within a concrete structure, surrounded on all sides by concrete after the concrete is poured. This creates a direct and intimate contact between the conduit and the concrete. Think of conduit running within a concrete floor slab, concrete wall, or buried underground in a concrete encasement.

Purpose of the Prohibition (NYC Amendment 344.10)

The prohibition against aluminum RMC encased in concrete is generally due to concerns about the potential for corrosion. Concrete is porous and alkaline. Over time, moisture can penetrate the concrete and, when in direct contact with aluminum, create a corrosive environment. The NYC amendment, like others, is intended to prevent this degradation.

Fire-Stopping Material

The purpose of fire-stopping material around the conduit penetration is fire protection. The material's primary function is to create a fire-resistant barrier, preventing the spread of fire and smoke between floors. While it fills the space around the conduit, it doesn't have the same properties or potential to cause corrosion as concrete. It is specifically engineered not to corrode materials.

Distinction

There is a significant difference between:

Encasement

Aluminum RMC is physically within concrete and concrete is around its outer surface.

Penetration

Aluminum RMC penetrates a small area in a slab and is sealed with fire-stopping material.Therefore, punching through a concrete slab and sealing with approved fire-stopping material does not constitute "encasement in concrete" as prohibited by NYC's amendment 344.10. You are correct in assuming it's acceptable under the code.

Important Considerations



Manufacturer's Instructions

Always consult the manufacturer's instructions for the specific fire-stopping material used. These instructions will specify the required depth and installation methods to maintain the integrity of the fire-rated barrier.

Local Inspection: While the interpretation above is generally accepted, it is always wise to discuss specific installations with the local electrical inspector. The inspector has the final authority on code interpretations within their jurisdiction. They can confirm that the proposed method of installation meets the intent and letter of the code.In summary, you're on the right track. Passing through the slab and fire-stopping is acceptable, while encasing it in concrete is prohibited. Flag for review