Cable Gland Size Chart: NEC-Compliant Sizing, Selection & Best Applications
Selecting the correct cable gland for an electrical installation is more than just a routine task—it ensures safety, reliability, and compliance with electrical standards. A well-designed system depends heavily on proper cable sizing and matching it with an appropriate gland. Engineers, electricians, and industrial technicians often rely on a cable gland size chart to streamline this process, reducing errors and preventing downtime. This guide provides practical insights into NEC-compliant sizing, selection tips, and industrial applications.
Table of Contents
Table of Contents
Cable Gland Size Chart by Cable Diameter
Selecting the correct cable gland size is essential for maintaining the cable’s IP rating, providing adequate strain relief, and ensuring a safe, reliable installation. Cable glands are selected based on the cable’s outside diameter (OD), not the conductor cross-sectional area (mm² or AWG). Always refer to the cable manufacturer’s datasheet and the gland manufacturer’s clamping range before making a final selection.
| Cable Gland Size | Typical Cable OD Range (mm) | Common Cable Size* | Thread Type | Typical Mounting Hole (mm) | Suitable For | Typical Applications |
|---|---|---|---|---|---|---|
| M12 | 3–6.5 | 0.5–1.5 mm² | Metric | 12 | Unarmored | Sensors, instrumentation |
| M16 | 4–8 | 1.5–2.5 mm² | Metric | 16 | Unarmored | Control panels, PLC wiring |
| M20 | 6–12 | 2.5–6 mm² | Metric | 20 | Unarmored | Lighting, small power circuits |
| M25 | 11–17 | 6–16 mm² | Metric | 25 | Armored & Unarmored | Distribution boards, motors |
| M32 | 15–21 | 16–35 mm² | Metric | 32 | Armored & Unarmored | Industrial feeders, MCCs |
| M40 | 19–28 | 35–70 mm² | Metric | 40 | Armored & Unarmored | Large power cables |
| M50 | 27–35 | 70–120 mm² | Metric | 50 | Armored & Unarmored | Transformers, switchgear |
| M63 | 34–44 | 120–240 mm² | Metric | 63 | Armored & Unarmored | Utility feeders, substations |
| PG7 | 3–6.5 | Up to 1.5 mm² | PG | 12.5 | Unarmored | Electronics, instrumentation |
| PG9 | 4–8 | 1.5–2.5 mm² | PG | 15.2 | Unarmored | Control equipment |
| PG11 | 5–10 | 2.5–4 mm² | PG | 18.6 | Unarmored | Junction boxes |
| PG13.5 | 6–12 | 4–6 mm² | PG | 20.4 | Unarmored | Small distribution panels |
| PG16 | 10–14 | 6–10 mm² | PG | 22.5 | Unarmored | Industrial control cabinets |
| PG21 | 13–18 | 10–25 mm² | PG | 28.3 | Armored & Unarmored | Motor and power cables |
| PG29 | 18–25 | 25–50 mm² | PG | 37 | Armored & Unarmored | Heavy industrial applications |
| PG36 | 22–32 | 50–95 mm² | PG | 47 | Armored & Unarmored | Power distribution |
| PG42 | 32–38 | 95–150 mm² | PG | 54 | Armored & Unarmored | Large feeders |
| PG48 | 37–44 | 150–240 mm² | PG | 59.3 | Armored & Unarmored | Utility and substation installations |
*Cable size is a general reference only. The cable’s outside diameter (OD) is the primary criterion for selecting a cable gland.
Installation Tip: For NEC-compliant installations, choose a cable gland from Cable Gland Size Chart with the correct ingress protection (IP66, IP67, or IP68) and ensure it is listed or certified for the installation environment. In hazardous (Classified) locations, use appropriately certified explosion-proof cable glands that comply with the applicable NEC Articles and local electrical codes.
Understanding Cable Glands
Cable glands are mechanical devices that secure and seal the ends of cables entering electrical enclosures, panels, or equipment. They provide strain relief, environmental protection, and maintain electrical integrity. The correct gland ensures the cable remains firmly fixed while preventing moisture, dust, or chemical ingress. Industrial environments, particularly those with high voltage or harsh conditions, demand precise gland selection.
Key benefits of using the right cable gland include:
- Protection against mechanical stress and vibrations
- Maintaining IP rating and environmental sealing
- Preventing electrical hazards such as short circuits
- Extending cable life and system reliability
Importance of NEC-Compliant Cable Glands
The National Electrical Code (NEC) sets strict standards for electrical safety in the United States. NEC-compliant cable glands must meet mechanical, thermal, and environmental requirements to ensure safe operation. Engineers must verify that the gland selected matches both the cable size and type, as well as the application environment, whether industrial, commercial, or outdoor.
Some NEC requirements include:
- Proper grounding and bonding where required
- Correct strain relief based on cable diameter and weight
- Material selection suitable for temperature, chemical exposure, and UV resistance
How to Use a Cable Gland Size Chart
A cable gland size chart simplifies the process of matching cable diameter with the appropriate gland size. Engineers can quickly determine the correct gland by referencing the cable type, conductor size, and insulation thickness. Most charts list both minimum and maximum cable diameters for each gland size, ensuring a secure fit without over-compression.
Factors to Consider for Gland Selection
When selecting a cable gland, several factors must be evaluated beyond just size:
- Cable Type: Armored cables require glands with grounding capability, whereas flexible cables need strain relief.
- Environmental Conditions: Outdoor or chemical-heavy environments require corrosion-resistant materials such as stainless steel or brass.
- Mechanical Load: Heavy-duty installations demand robust glands to handle the cable’s weight and vibration.
- Temperature Rating: Ensure the gland material can withstand the operating temperature of the cable and surrounding environment.
- Ingress Protection (IP) Rating: Choose glands with adequate sealing to prevent dust and water ingress, especially for industrial applications.
Industrial Applications of Cable Glands
In industrial settings, cable glands are used extensively to protect power, control, and instrumentation cables. Their role is critical in manufacturing plants, oil and gas facilities, chemical plants, and data centers. Correct sizing prevents downtime and ensures continuous operation.
Typical applications include:
- Electrical control panels in factories
- Power distribution boards in commercial buildings
- Instrumentation cabling in process industries
- Outdoor installations exposed to UV, rain, or corrosive elements
Practical Tips for Engineers
- Always measure the cable diameter at its thickest point, including insulation.
- When in doubt, select a slightly larger gland to prevent compression of the cable.
- Verify the gland material compatibility with both the cable jacket and the environmental exposure.
- Cross-check with the NEC and local standards for compliance.
- Keep a reference cable gland size chart accessible on-site for quick selection.
Conclusion
Using a cable gland size chart is an essential practice for engineers and technicians aiming to ensure NEC-compliant, reliable, and safe electrical installations. Proper gland selection prevents mechanical failures, environmental ingress, and electrical hazards, particularly in industrial settings where cable performance is critical. By following standard charts, considering application-specific factors, and understanding NEC guidelines, professionals can confidently design and maintain systems with optimal performance and safety.
Accurate cable sizing combined with the right gland enhances system reliability, reduces maintenance costs, and ensures long-term safety for electrical installations. For engineers and industrial professionals, a cable gland size chart is not just a reference—it is a practical tool for achieving high-quality electrical design.
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