wire ferrules

[megloff11x]

I've seen a bunch on sticking stranded wires, particularly fine stranded, into terminal blocks with the screw down type clamping action leading to smoked terminal blocks and wires. I always use wire ferrules, which in addition to looking neater, also prevent that "one hair into the next terminal" effect. Does UL have anything to say on the subject?

 

[tony_psuee]

meg...,

I am reaching back a few years to when I was an application engineer for a terminal block company. The screw clamp blocks are listed for use without ferrules. That was often a selling point they used. Where ferrules are of benefit is with multiple conductors. The blocks are typically only listed for two conductors under a screw. UL looks at a ferrule as a single conductor. So, provided the total area of the ferruled wires doesn't exceed the max area of the terminal block you could ferrule several wires together and insert into the block without violating the UL approval. Of course your ferrule has to be be listed for multiple conductor too. You have to remember with UL the testing takes place under ideal conditions.

Tony

 

[petersonra]

One thing that is a huge problem with small stranded conductors is that they are fairly fragile. Use of a ferrule reduces the strain on the individual strands.

I have seen many small stranded conductors with broken strands when under a saddle at a terminal. Better to put the strain on the ferrule IMO.

I have yet to come across any terminal that is suitable in the real word for terminating stranded conductors smaller than #18 or so. That does not necessarily mean there is not one out there, but I have tried all kinds of them, and they have the same problems.

The same problem happens when you use any size wire with fine strands.

 

[dsteves]

Good afternoon, Bob, I also agree with that. We've built several machine control panels here, many of which use hundreds of A-B 1492-W4 type terminal blocks. Much of the wiring is 18AWG UL1007 between the PLC components and the terminal blocks. The I/O wiring could be smaller still, in the case of servo resolver signals, for example. The ferrules make the connection inside the terminal block much more secure, especially with conductors smaller than 18AWG.

Dan

 

[mdshunk]

Stranded wires in terminal blocks is often okay until some factory maintenance man starts troubleshooting and replacing things. This results in conductors that are re-terminated with less than ideal results. Ferrules sort of "idiot proof" the installation, in my opinion. (No offense to idiots. I'm sympathetic to your disability).

 

[peteo]

Last I heard, couple years ago, 'ferrules' as a generic term, applies more to CE equipment. This is a big issue to some, as related terms such as 'touchproof' and 'din rail' and 'self certify' are related sticky issues. So the last I remember, they're required for any stranded for CE product, and NEMA 'likes' them, but they're not required by UL for general wiring.

The place I've always found good info related to ferrules was at Panduit. I've used reel after reel of Ed's Terminal Company (Molex-ETC) product, not only only on the ultraflex, but have found those panduit pages most informative.

 

[RayS]

I have yet to come across any terminal that is suitable in the real word for terminating stranded conductors smaller than #18 or so. That does not necessarily mean there is not one out there, but I have tried all kinds of them, and they have the same problems.

I really like the WAGO's. Iv'e heard others swear at 'em because the're different, but I thought they made a great connection while being kind to the conductors

link for the sensor blocks
http://www.wago.us/83.htm?L1=/produ...L3=/products/141.htm&HL3=&B=/products/133.htm

 

[alfredo]

UL Dilemma

UL Dilemma

I am the manager of a company that specializes in the sale of wire ferrules.
The issue of UL recognition for ferrules comes up routinely, specially from UL508A companies that inquire whether our ferrules are UL recognized.
We normally tell them that they are not, simply because UL has not, to our knowledge, issued a set of standards relating to this category of terminals.
When we are asked why we cannot apply to our ferrules the same UL standards issued for pin terminals, we point out that there are many differences between ferrules and traditional terminals, including a very important one, which is:
In the case of ferrules, a stranded wire is inserted into the ferrule and crimped, thus becoming an integral part of the wire. The crimped ferrule is then inserted into the terminal block and tightened either by clamp or screw.
In the case of pin terminals, the wire is crimped through the terminal's insulation (which is much thicker than that of the ferrule) and the pin (not the wire) is inserted into the terminal block.
I believe that the pull out requirements set forth in the UL Standards relating to pin terminals (or similar terminals) cannot be applied to ferrules, simply because one cannot expect a ferrule (which has much thinner walls than the aforementioned terminals) to pass pull out tests expressly designed for other terminals.