Okay, Steve, let's break down the code requirements for your emergency stop pushbutton installation in the spray paint booth. You've got a good understanding of the basics, but let's clarify a few points to ensure compliance.

Understanding the Code References



501.15(A)(1)

This section typically requires sealing fittings to prevent the passage of gases, vapors, or dusts from one portion of the electrical system to another through the conduit. In this case, it's likely referencing the requirement for a seal within a certain distance of an explosionproof enclosure (like your pushbutton box) containing arcing devices.

501.15(A)(4)

This is the key section addressing the boundary between a Class I, Division 1 (C1D1) location and a non-hazardous location. It does require a sealing fitting where the conduit crosses that boundary. The 10-foot rule you mentioned applies to the location of this boundary seal.

Analysis of Your Situation

You're describing a scenario where the conduit run goes from inside the C1D1 spray booth (where the pushbutton box is located) to outside the booth, using two 90-degree explosionproof fittings and a sealing fitting.Here's the critical point:

The sealing fitting required by 501.15(A)(1) does NOT necessarily satisfy the requirement of 501.15(A)(4). Reasoning

501.15(A)(1) is about containing potential ignition within the explosionproof enclosure and preventing propagation within the hazardous area's wiring system. 501.15(A)(4) is specifically about preventing the migration of flammable vapors from the hazardous area out into a non-hazardous area. They serve distinct purposes.

Answer to Your Question



You likely need a second sealing fitting at the C1D1 boundary, even though you have one within 6 feet of the boundary. NEC Requirement

The NEC generally requires a sealing fitting where the conduit leaves the Class I, Division 1 location (501.15(A)(4)). This fitting must be located within 18 inches of the boundary. (2023 NEC)

Best Practice and Clarifications


Location of the Boundary Seal

The boundary seal needs to be as close as practical to where the conduit exits the C1D1 area, usually immediately after the last fitting before transitioning to the non-hazardous area. The 10-foot rule simply allows flexibility, but it does not negate the requirement for the seal where the conduit leaves the C1D1 area. The 18 inch requirement is more specific and applicable in your situation.2.

Type of Seal

Ensure you use the correct type of sealing fitting, with the appropriate sealing compound, and follow the manufacturer's instructions for installation. Sealing fittings must be accessible.3.

Drainage

Consider whether condensation or other liquids could accumulate in the conduit run. If so, you might need a drain in the conduit system before the boundary seal, on the hazardous side.4.

AHJ Approval

Always consult with your local Authority Having Jurisdiction (AHJ) for their specific interpretation and requirements. They have the final say on code compliance. They may have local amendments to the NEC.

In summary: While your first sealing fitting is important for containing potential explosions within the hazardous area's wiring, you likely still need a separate sealing fitting where the conduit exits the Class I, Division 1 location, near the physical boundary of the spray booth. Confirm all details with your AHJ. Flag for review