Re: Twist on Connectors

George . Waters Fri, 29 May 1998 21:57:46 +0000

     
     
     Crimp connectors are absolutely repeatable and infallible....  Yes you did 
     say if they were made with the right tool.  Here's a case where they were 
     not.
     
     A little while ago I was struggling with the issue of failed crimp 
     connectors.  (no vendor names to protect the innocent).  The two failure 
     modes I saw were
     1.   The wire was inserted too far, so that insulation entered the 
     electrical part of the crimp.  Electrical contact was made, but not well, 
     since the crimp was held open by the insulation.  The connection 
eventually 
     overheated and failed.
     2.   The crimp was made so hard that many of the stranded conductors were 
     severed, again leading to eventual overheating.

______________________________ Reply Separator _________________________________
Subject: Twist on Connectors
Author:  [email protected] at PMDF
List-Post: [email protected]
Date:    5/28/98 18:11

Hi Ray.

You wrote:

<My question is: are twist on type connectors allowed for this type of 
equipment in Europe? Is there any standard or guide lines that I could 
refer to? Most standards that I have reviewed, only state that the 
connection must be reliable. So if there is an IEC standard for twist 
on connectors, and these connectors meet that standard, would not they 
be considered reliable?>

These are the ceramic internal corkscrews, right?   My answer would be that 
I would not design with these, and I would not recommend anybody use them. 
I've seen them used all over the world in various forms and I've never seen 
them fail, but then I've seen  wooden houses, Ford Model 'T's and antique 
clocks all working perfectly, doesn't mean they are the best way to go.

Crimped connections done with a proper tool are absolutely repeatable, and 
infallible.  My dog could do a good crimped joint if I put the tool in his 
mouth.  Twist on connectors joints are just too variable in quality, 
depending on grip strength, oily fingers, thickness of strands, anneal 
state of the copper, how much wire has been stripped, etc. etc. To meet 
IEC1010 the tracking and air distances would have to be better than 
minimum, something not predictable with twist-on's, particularly if they 
are subject to some pull, when they unwind a bit.   If I told a Law Court 
or Insurance Company that we used these things to save a few cents, there 
would be a hushed silence before they pulled the lever.

Why stop there?  Why not use cotton wound insulated wire, or Vulcanised 
India Rubber mains cables, they were great in their time, but modern 
materials and methods have made them obsolete, not failures, but obsolete.

In the States I saw a chap throw away the DIN standard 40 amp terminal 
blocks we provided in a motor casing, and wind the feed and motor winding 
tails round a bolt which had a washer and nut run on, tightened, then 
wrapped in PVC tape.  The chap explained that 'He couldn't be doing with 
the terminals, he wanted the two wires to actually touch'.  To my ultimate 
shame I couldn't think of anything to say.

Just a few not-so-humble self opinionated cents worth...  :-)

Chris Dupres
Surrey, UK.

Date: Thu, 28 May 1998 19:11:17 -0400
From: Chris Dupres <[email protected]>
Subject: Twist on Connectors
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Re: Twist on Connectors

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