Are bootlace ferrules OK for use in NorthAm.

[MarkGallimore]

Hi,

I'm building a single test rig which will be used in North America. The equipment will be examined by a NTRL. The equipment will be made in accordance with IEC 61010 (electrical lab equipment). In the UK (where the equipment is being manufactured) in addition to crimp terminals we use bootlace ferrules to terminate equipment conductors. I have tried, unsuccesfully, to find UL approved bootlace ferrules for this equipment. This makes me wonder if they are not allowed for use in equipment designed for the North American market. This view is reinforced by the fact that the colour options for the plastic sleeves seem to be in French and German colour ranges. Can someone shed some light on this for me please.

 

[Kiljoy]

I'm more familiar with industrial control panels than test equipment, but since no one else has attempted to answer your question, I will give it a shot.
I do not believe that they are not allowed as they are not required in UL panels. Since the wires should be terminated at a device or terminal block with the appropriate binding screw or cage clamp, the bootlace ferrules are not needed.
We had the opposite problem with sending CE panels to Europe. We couldn't figure out if ferrules were required or not. Our electricians didn't have the correct crimper and they all came off in the terminal blocks. Perhaps you can enlighten me on their required use.

 

[MarkGallimore]

Thanks for the reply Kiljoy.

I'm no expert with ferrules for use in either North America or Europe and what I've written below is my layman's understanding of what I've been told rather than what I've read from any standards.

I contacted several European boot lace ferrule suppliers and distributors and none sold UL approved versions. Some claimed too sell them to American companies.

The purpose of the ferrule is to prevent splaying of the individual strands on a multi core conductor (presumably to make it easier to insert into a terminal block and to minimise the chance of loose strands bridging the next conductor). The "fastness" of the conductor is still dependent on the clamping screw and not the firmness of the ferrule alone on the conductor. For that reason there is apparently no standard to determine ferrule / conductor pull off strengths.

I was told that the ferrule helps to distribute the screw clamping load more evenly across the individual strands rather than clamp and potentially damage a subset of the strands. I guess that sounds reasonable but crushing the ferrule will also use up some of the torque applied to the screw and so the clamping load left to grip the conductors must be reduced.

Sorry I can't be much more help. I'm just suprised by how difficult it's been to find any clear factual information.

Any clues from anyone else would be appreciated.

I've failed to see anything in either ien60204 or ien61010 which discusses the use of ferrules (doesn't mean I simply failed to see it though).