Understanding the difference between zip ties is essential to use the correct tie for certain applications. Because of the cable tie classifications standards, you might have heard Type 21S cable ties are the best in use for construction and other industrial applications. Type 21S cable ties are rated to retain 100% tensile strength no matter the conditions while also qualifying as long-term performance and supporting conduit cables in construction. In this blog, we explain Type 21S cables and their rating.
What Are the Classifications of Cable Ties?
If cable ties meet the requirements of cable management systems as outlined by the International Electrotechnical Commission (IEC), Underwriters Laboratories (UL), and Canadian Standards Association (CSA) in Standard 62275, they are categorized as Type 1, 11, 2, 2S, 21, or 21S. According to National Electrical Manufacturers Association (NEMA) cable ties are classified as:
- Type 1 (Nonmetallic and Composite Cable Ties): Retains 100% of as-received declared loop tensile strength and a minimum 50% of declared loop tensile strength after specified test conditions.
- Type 11 (Nonmetallic and Composite Cable Ties): Type 1 with additional pre-qualification to long-term performance characteristics of nonmetallic molding materials in accordance with the UL Component Plastic Materials Certification Program (QMFZ2).
- Type 2 (Metallic, Nonmetallic and Composite Cable Ties): Retains 100% declared loop tensile strength after specified test conditions.
- Type 21 (Nonmetallic and Composite Cable Ties): Type 2 with additional pre-qualification to long-term performance characteristics of nonmetallic molding materials in accordance with the UL Component Plastic Materials Certification Program (QMFZ2).
- Type 2S and Type 21S (Metallic [2S only], Nonmetallic and Composite Cable Ties): Type 2 or Type 21 with additional qualification for suitability to support conduit and cables in building construction in accordance with the requirements in relevant national installation codes.
Each of these classifications allows manufacturers to consistently meet universal standards, ensuring the safety of different types of cable ties. In addition to pre-qualification and long-term performance, the Type 11 and Type 21—including 21S—classifications provide a number of advantages, including a higher degree of safety in the design of the final product, uniformity in test results, and the availability of material performance data.
How Are Zip Ties Rated?
Zip ties are rated based on tensile strength and materials, determining their suitability for certain applications. For example, Type 21S zip ties are approved to support conduit and cables in building construction, whereas other cables might only be rated for lighter loads based on their tensile strength.
What Is UL Type 21S?
According to the applicable installation codes, Type 21S refers to products that can hold and support flexible metal conduits and cables in construction. These cable ties have the strictest test requirements, such as the 2017 National Electrical Code (NEC) and the 2015 Canadian Electrical Code (CEC). The higher tensile strength and superior thermal characteristics of Type 21S cable ties, which are UL approved, set them apart from standard cable ties.
According to NEMA, “Type 21 products are required to be molded from polymeric materials that have been separately evaluated according to UL 746A, Polymeric Materials-Short Term Property Evaluations, and UL 764B, Polymeric Materials- Long Term Property Evaluations, or CSA C22.2 No. 0.17, Evaluation of Properties of Polymeric Materials.” Products of Type 21S are identical to those of Type 21 except for:
- Tensile strength of a cable tie loop with a declaration of no less than 50 lbs (220 N).
- Mechanical strength of the fixing device or integral device with a minimum declaration of 50 lbs (220 N).
- Maintain test load for five minutes with no excessive slippage as stated in the specification.
Are Type 21S Cable Ties Plenum Rated?
Yes, Type 21S cable ties are plenum rated, meeting the UL Standard 62275 and Section 300.22 of the National Electric Code. What are plenum rated cable ties? Plenum rated cable ties are made from premium materials that pass local fire regulations and are intended to be installed into plenum spaces, like the space between a drop-down ceiling and a structural ceiling. Plenum rated ties are self-extinguishing and highly resistant to chemicals and abrasion. Cable ties in these spaces are approved for installation in areas of air circulation for heating, ventilation, and air conditioning. If you need to identify plenum cable ties, typically they are maroon or burgundy in color.
Cable Ties for All of Your Needs
At ZipTie.com, we offer cable ties for all applications with tensile strengths ranging from 18 lbs to 350 lbs. We provide a large selection of cable ties, including a number of highly customized choices, to meet your needs, no matter what they may be. With our quality guarantee, we ensure you’ll receive the best product for your needs. You can browse our whole selection of zip ties if you’re searching for the best ties on the market, or call us at +1-855-947-8433 between 8:30 AM and 5:30 PM ET to discuss your particular needs.