Hello Brian,
Off hand, I am unaware of anything preventing the use of a twist-on wire connector in portable equipment, but that doesn’t mean that the prohibition doesn’t exist. Other list members may know of specific cases where the connectors are prohibited. However, the description of the connector covered in electrical tape indicates that the connector is likely used outside of its UL Listing (if it is even a Listed connector.) First, let me state that “Wire-Nut” is a registered trademark of Ideal Industries. If you are looking for information in standards, the term “twist-on wire connector” will be used. Vibration during use is probably not the main issue. There are many types of fixed equipment, such as an air conditioner or other motor driven appliance, where twist-on connectors are used and they are subject to regular vibration. The connectors may see more vibration in these applications than they might see in some portable appliances. However, your description gives me cause to be concerned. UL does List twist-on connectors under category code ZMVV and they have been around for quite a while. (Ideal’s UL file number is E5238 and that should give you an idea as to the age of the product.) The connectors’ Listing does have some very specific requirements. Specific size connectors are Listed only for use with specific wire sizes and types. The installation instructions must be followed closely. Some of the wire connectors specify that you should not twist the wires first. The twisting of the wire connector will twist the wires to make the proper connection. If you see a connector covered with black tape, there is likely a problem. The tape is typically used when there is a concern that the connector will come loose. This is done based on the installer’s experience. If they have had connectors come loose, it is because they are likely using them incorrectly. The tape does not fix anything. Electrical tape will not likely withstand the test of time and the adhesive will degrade. Cheap electrical tape rarely lasts long at all. There are numerous crimp connectors suitable for connecting wires. There are but splices and crimp connectors designed to perform the same purpose as a twist-on connector. The crimp connectors make a good, permanent splice. The twist-on connector is intended for use where connections are made in the field, particularly where they may need to be undone for servicing. Crimp connections and terminal blocks are better options for factory connections. Ted Eckert Compliance Engineer Microsoft Corporation ted.eck...@microsoft.com The opinions expressed are my own and do not necessarily reflect those of my employer. From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Monday, November 17, 2008 6:18 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: What's the deal with Wire Nuts? Greetings Experts. This should be an easy one for those who know the answer. What is the deal with Wire Nuts? Where can be they be used, where can’t they be used? Are there different rules for permanently mounted equipment verse portable equipment? Do you have to also use a mechanical device such are a tie wrap? How about black tape? Our company does not use wire nuts but we always had the impression that safety inspectors do not like to see wire nuts in portable equipment. We are evaluating a product made by another company that uses wire nuts on primary wiring with black tape wrapped around it. Is this technique acceptable internationally on portable equipment? Thanks to all in advance for the education. The Other Brian _________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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