Okay, let's break down the requirements for seal-offs in hazardous locations, specifically related to a propane tank pump motor connected with rigid conduit.

Understanding the Code and Seal-Offs Hazardous Locations

Because you're dealing with a propane tank (likely a Class I, Division 1 or 2 location depending on the specific circumstances), the area around the tank and associated equipment is classified as a hazardous location. Propane is a flammable gas, and electrical equipment must be installed to prevent ignition of the gas.

Seal-Offs Purpose

Seal-offs are designed to prevent the passage of gases, vapors, or flames from one portion of the electrical system to another. They are filled with a sealing compound after the wiring is installed. They achieve this by limiting the passage of gases and flames that might travel through the conduit system.

Specific Requirements Based on Your Scenario

Here's how the National Electrical Code (NEC) likely applies to your situation (assuming U.S. standards): Seal-Off at the Motor (Required)

You are correct that a seal-off is required at the motor. Specifically:

Within 18 inches

NEC typically requires a seal-off within 18 inches (457 mm) of enclosures that contain arcing, sparking, or high-temperature components. Motors fall into this category.

Seal-Off at the Panel (Potentially Required, Depends on Factors)

This is where things get more nuanced. You might need a seal-off at the panel, depending on several factors:1.

Classification Extent

The key question is how far the hazardous location extends.

Division 1

If the entire 100-foot conduit run is considered to be within a Class I, Division 1 location, then yes, you likely will need a seal-off at the point where the conduit leaves the hazardous location and enters the non-hazardous area (presumably at the panel).

Division 2

If the entire 100-foot conduit run is considered to be within a Class I, Division 2 location, then you may need a seal-off if the panel contains devices that may produce arcs, sparks, or high temperatures in normal operation.2.

Conduit Length

NEC Article 501.15(A)(1)(3) contains conduit fill limits depending on the trade size of the conduit. Trade sizes 2" and smaller should not exceed a 40% fill. Trade sizes 2.5" and larger should not exceed a 25% fill.
3.

Panel Location

If the panel is located in a non-hazardous location, you will still need to install a seal-off fitting within 18 inches of where the conduit leaves the hazardous location and enters the non-hazardous location.

Crucial Considerations and Steps to Take


Hazardous Location Classification

This is paramount. You must determine the Class and Division for the area around the propane tank and the conduit run. This determination should be made by a qualified person (engineer or inspector) familiar with hazardous location classification. This classification will dictate many of the requirements.2.

Local Codes and Inspections

Always adhere to local codes and regulations, which may be more stringent than the NEC. Consult with your local electrical inspector.3.

Panel Type and Components

Evaluate the panel itself. Does it contain any devices that could produce arcs, sparks, or high temperatures (e.g., breakers, contactors, relays)? If so, and if the panel is in the hazardous location, seal-offs may be needed at the panel.4.

Proper Seal-Off Installation

When installing seal-offs: Use the correct type of seal-off fitting for the conduit size and hazardous location classification. Follow the manufacturer's instructions for filling the seal-off with sealing compound. Use the appropriate compound (typically a two-part epoxy-like material). Ensure the seal-off is properly packed and that no voids or air pockets are present.

In Summary

While a seal-off is required at the motor, the need for a seal-off at the panel is conditional. It depends heavily on the hazardous location classification, the panel's location, and whether the panel contains arcing/sparking components.

Do not proceed without a proper hazardous location classification and consultation with a qualified electrical inspector or engineer. Safety is the top priority when dealing with flammable gases. Flag for review