When working with electrical enclosures, junction boxes, or industrial panels, one small component can make a big difference: the cable gland. A properly selected NPT cable gland not only seals and secures your wiring—it ensures the entire system remains waterproof, safe, and long-lasting.
But with multiple sizes, thread types, and material options available, how do you know which gland is right for your setup?
This guide will help you confidently select the right NPT cable gland for your next project.
What Is an NPT Cable Gland?
An NPT (National Pipe Thread) cable gland is a type of threaded connector used to secure and seal the end of an electrical cable entering an enclosure. It’s widely used in North America and conforms to the tapered NPT threading system, which creates a tight fit as it is screwed in.
Key functions include:
- Sealing against water, dust, and debris (IP65/IP68 rated)
- Providing strain relief to reduce cable fatigue
- Ensuring a stable mechanical connection between the cable and housing
Factors to Consider When Choosing an NPT Cable Gland
1. Thread Size (NPT Standard)
Match the thread size of your enclosure’s knockout or entry port. Common sizes include:
- NPT 1/4″
- NPT 1/2″
- NPT 3/4″
- NPT 1″
Ensure your panel or box has NPT-compatible threads or use an adapter if needed.
2. Cable Diameter Range
Choose a gland with a sealing range that fits your cable’s outer diameter. For example:
| NPT Size | Cable Range |
|---|---|
| 1/4″ | 4–8 mm |
| 1/2″ | 6–12 mm |
| 3/4″ | 12.5–18 mm |
| 1″ | 18–25 mm |
Too small, and your cable won’t fit. Too large, and you risk water ingress or strain issues.
3. Strain Relief Type
For cables subject to motion, vibration, or bending, consider a spiral strain relief gland like the LeMotech NPT Spiral Cable Gland. The spiral sleeve reduces stress at the cable entry point and extends cable life.
4. IP Rating
Outdoor or wet applications require glands rated at IP68 for complete water and dust sealing. Be sure the included washer and seal are installed correctly.
5. Material
- Nylon (PA66): Lightweight, corrosion-resistant, affordable
- Metal (Brass/SS): Durable, but conductive and more expensive
- EPDM Seals: High temperature and chemical resistance
For most control boxes and field installations, nylon NPT cable glands offer the best balance of performance and cost.
Application Scenarios
- Outdoor junction boxes (e.g., LeMotech IP65 series)
- Solar combiner boxes
- Marine and RV electrical wiring
- Factory automation panels
- Smart home controller hubs
Product Recommendation
LeMotech NPT Spiral Cable Gland (IP68 Rated)
- Flexible spiral relief
- IP68 waterproof
- Available in multiple thread sizes
- Includes locknut, gasket, and sealing nut
- Built from tough PA66 nylon
Conclusion
Choosing the right NPT cable gland ensures your wiring remains secure, sealed, and stress-free. From proper thread size to cable diameter and strain relief needs, making the right choice at the entry point helps protect your entire system.
Explore our full range of waterproof cable glands at lemotech.com