--- title: Interpower’s Answers to Commonly Asked Questions—Designing Your Power System Components Product with the Correct Cord Set description: Interpower explains why you should not use two wire cable with a three wire connector or vise versa. The first reason would be that equipment with a Class I inlet needs to be grounded for safety and emission reasons. image: https://blog.interpower.com/hubfs/Interpower_March2018/Images/Wendy.jpg --- [![Interpower Facebook](https://blog.interpower.com/hubfs/Interpower_March2018/Images/facebook-button-black.png "Interpower Facebook")](https://www.facebook.com/interpowercorporation) [![Interpower LinkedIn](https://blog.interpower.com/hubfs/Interpower_March2018/Images/linkedin-button-black.png "Interpower LinkedIn")](https://www.linkedin.com/company/interpower-corporation) [![Interpower Twitter](https://blog.interpower.com/hubfs/Interpower_March2018/Images/twitter-button-black.png "Interpower Twitter")](https://twitter.com/interpowergroup) **PHONE:U.S.** [(641) 673-5000 |](tel:6416735000) **Toll Free:** [(800) 662-2290 |](tel:8006622290) **UK** [+44 (0)1908 295300 |](tel:+4401908295300) **Freephone:**[00800 5566 5566](tel:0080055665566) [![Interpower](https://blog.interpower.com/hubfs/Interpower_March2018/Images/IC-white-site-heading.png "Interpower") ![Interpower](https://blog.interpower.com/hubfs/Interpower_March2018/Images/mobile-logo.png "Interpower")](http://interpower.com) - 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[Tweet](https://twitter.com/share) ![Designing Your Power System Components Product with the Correct Cord Set](https://blog.interpower.com/hs-fs/hubfs/Interpower_March2018/Images/Wendy.jpg?width=250&height=183&name=Wendy.jpg) At the Interpower Group of Companies, we have real people answering the phones. No recorded messages. As a result, we receive a number of interesting product design questions. Usually if a question has been asked by one person, it means that others also have the same question. So to assist you, we will be sharing a few of the commonly asked questions, complete with answers. Be sure to follow our series, “Interpower’s Answers to [Commonly Asked Questions](http://www.interpower.com/ic/designers/webcasts/commonly-asked-questions.html).” *Question:* Why can’t I use a two-wire cable with a three-wire connector or vice versa? *Key points:* - Equipment with a Class I inlet needs to be grounded for safety and emission reasons - UL 817, IEC 60799, CSA C22.2 No. 21, and equipment standards are specific to that application *Answer:* Ron Barnett, Product Development Manager, explained why this configuration cannot be done. “If equipment is supplied with a Class I plug—a plug with a ground connection—for safety and emission reasons it must be connected to an outlet with a ground connection,” Barnett said. “You need to design your product with the correct cord to prevent shock hazards.” “Usually we hear of two scenarios,” Barnett said. “The first relates to customers designing Class II equipment—that is equipment with no earth ground connection—with the wrong cord. They ask us to make a cord using a Class I plug, cable with three conductors, and a Class II connector. This configuration does not connect the earth ground wire in the connector.” “The second one is when customers design Class I equipment—that is equipment with an earth ground connection—with the wrong cord. They ask us to make a two conductor cord with a three terminal connector. This application demands a three wire cord with a true earth ground [connection ](http://www.interpower.com/ic/designers/Interpower-Connections.html)via a three conductor connector and plug. Without the ground connection, you create a potential shock hazard,” Barnett said. The key point is customer safety. Equipment manufacturers should use cords that are safe and that comply with the relevant product safety standards. The safety of cord sets and power cords is demonstrated by having them tested and certified to the applicable standards, such as UL 817, IEC 60799, and CSA 22.2 No. 21. If you have other questions, Interpower offers free technical support. You can check the website at [www.interpower.com](http://www.interpower.com/), e-mail [sales@interpower.com](mailto:sales@interpower.com) (United States) or [uk@interpower.com](mailto:uk@interpower.com) (United Kingdom) or contact Customer Service in the United States at (800) 662-2290 or in the United Kingdom at +44 (0)1908 295300. If you have ideas for future *InfoPower* blogs, please e-mail [infopower@interpower.com](mailto:infopower@interpower.com). ## Stay In-The-Know with *InfoPower* The monthly *InfoPower* blogs are created to assist you in designing, building, and maintaining products for worldwide markets by providing you with information on topics relevant to power system components. ### Subscribe to Email Updates ### Recent Posts ### Posts by Topic ## [InfoPower Archive](http://www.interpower.com/ic/infopower-archive.html) ### United States 100 Interpower Ave Oskaloosa, IA 52577 | [info@interpower.com](mailto:info@interpower.com) Toll-Free Phone: (800) 662-2290 | Toll-Free Fax: (800) 645-5360 Phone: (641) 673-5000 | Fax: (641) 673-5100 ### United Kingdom 10 Kelvin Drive | Knowlhill, Milton Keynes | Buckinghamshire, MK5 8NH | UK | [uk@interpower.com](mailto:uk@interpower.com) **UK, Ireland, Germany, Switzerland, Austria** Freephone: 00800 5566 5566 | Freefax: 00800 5655 5655 **International:** Phone: +44 (0)1908 295 300 | Fax: +44 (0)1908 295301 © 2026 Interpower. 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