Hi, No, not from motor. This ring was in the motor starter box. The motor is 25 feet away. This ring took the circuit to a breaker in the motor starter box. The screw holding the ring was very tight. The back side of the ring looks fine. The discoloring of the crimped barrel suggests the heat was generated where the wire entered the barrel. I can see shiny faces on the ring where the screw must have compressed the ring to the terminal block. Neither the ring or barrel was cracked. Before I opened the barrel I could bend the wire and nothing in the barrel moved, the barrel crimp was quite tight. I will remove some insulation and see if there is a wire breaks, good idea. The only vibration would be a small amount when the breaker open and closes. The box was mounted on to plywood and that was on a cinder block wall. Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Upton, Shawn Sent: Wednesday, March 31, 2010 4:23 PM To: [log in to unmask] Subject: Re: [TN] Failed Ring Terminal Heat conducted up the ring terminal from the motor? What did the backside of the ring look like--did it make good contact, or was it lousy, causing higher current draw, which then over-heated the wire? I wonder how far down the wire that corriosion goes--I wonder if the wire resistance is high, causing the wire itself to be the heat source. Lastly, is that ring terminal cracked? It looks like it is almost broken in half. I also don't see a log of markings from the screw when you removed it--I'd expect fresh marks, scratches, from the bolt as it was removed. Might it be flex induced, cracking the ring, but also creating a broken wire a few inches away from the ring terminal? Shawn Upton, KB1CKT Test Engineer Allegro MicroSystems, Inc [log in to unmask] 603.626.2429/fax: 603.641.5336 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner Sent: Wednesday, March 31, 2010 3:55 PM To: [log in to unmask] Subject: [TN] Failed Ring Terminal Hi, Why would a crimped ring terminal fail and over heat? Can anyone suggest failure modes as to why the resistance would increase? I would guess a soldered connection would be better? See www.kondner.com/files/failedringterm.jpg That insulator was yellow at one time it is now brown and the insulation at that end of the wire is very brittle. The wire size is #10. This ring terminal came from a Furnas Electric motor starter for a 5hp 240V AC motor that draws about 28 amps. It was installed back in 1968. It was installed in a dingy barn in a silo pit where most of the steel enclosures are covered with rust. All kinds of nasty odors as there are plenty of cows in the area. It is quite amazing that it went this long, but I wonder why it failed. The crimp seemed tight but it had obviously over heated. Other such ring terminal on the same circuit are fine. The crimps were made in the factory and not by some guy with a simple hand tool. I ground off the edges which allowed me to open the crimp with minimal wire damage. I was surprised that much of the wire looked quite clean. I am just curious what folks would suggest. Thanks, Bob Kondner ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------