Everything You Need to Know About the Obscure Section 4A of Industrial Wiring Standard 23G

I have been working with industrial wiring for over 20 years, and in all that time, I have rarely needed to reference Section 4A of Standard 23G. However, for those interested in the obscure details of industrial wiring regulations, Section 4A covers some important but not widely understood topics.

Overview of Standard 23G

Standard 23G is the main regulatory document that governs industrial wiring in my region. It was first published in 1985 by the Regional Electrical Standards Board and has been updated periodically ever since. The standard is over 500 pages long and covers everything from conductor sizes to insulation requirements and more.

Section 4 specifically deals with installation methods and materials. It is further divided into subsections 4A through 4D, each dealing with a certain aspect of installation:

• 4A - Conduit and Tubing Installation
• 4B - Cable Trays
• 4C - Busways
• 4D - Other Wiring Systems

While sections 4B, 4C, and 4D see frequent use, section 4A is rarely referenced in my day-to-day work. However, it provides important guidance that cannot be overlooked.

The Obscure Section 4A - Conduit and Tubing Installation

Section 4A covers the proper installation methods for conduit and tubing systems. This includes:

• Minimum bend radii
• Maximum conduit fill
• Allowable conduit types by location
• Installation of expansion fittings
• Sealing requirements

Why Section 4A is Obscure

I have found section 4A to be obscure for a few reasons:

• Most industrial wiring uses cable trays - Conduit is reserved for short sections and final connections. Most conductors run through overhead cable tray systems.
• Basic install info is common sense - Things like bending radii and fill percentages are part of basic training.
• Exceptions for industrial environments - Industrial sites have more flexibility on sealing/expansion than commercial buildings.

However, while rarely used, 4A still contains valuable information. Thorough professionals should have a working knowledge of section 4A.

Key Topics Covered

Some of the key topics covered in section 4A include:

Minimum Bend Radii

• Table 4A.1 lists the minimum bend radii for various conduit sizes and materials. For example, 1/2" EMT conduit has a minimum bend radius of 4".
• Bending conduit too sharply can deform it and make pulling conductors difficult. Consult Table 4A.1 prior to bending.

Maximum Fill Percentages

• Table 4A.2 provides maximum fill for various conduit sizes.
• For example, the maximum fill for 1" rigid metal conduit is 40%.
• Exceeding maximum fill makes conductor pulls difficult and overheats conductors.

Approved Conduit Types

• Section 4A.III lists approved conduit types for general use, hazardous locations, and other special situations.
• For example, rigid metal conduit is required for mechanical rooms.
• Use of unapproved conduit types can violate building code.

Real World Examples

Though I seldom consult it directly, I frequently apply concepts from 4A:

• I verified minimum bend radii when installing 3/4" flex conduit for a CNC machine install.

• I confirmed approved conduit types when routing cables from a chemical storage room. Rigid metal was required.

• I calculated maximum fill when pulling a large feeder through 2" RMC. Exceeding 40% would have required bigger conduit.

So while it is obscure, Section 4A provides critical installation guidance. Thorough professionals benefit from knowing 4A well. Let me know if you need any other specifics on this forgotten section of Standard 23G!