Using ferrules - problems of resistance?

[xd400]

I'm not an electrician so this question may seem stupid.



I watch a lot of these electrician channels on youtube. One I saw recently on youtube showed the difference between cheap ferrule crimping sets and premium ones. The latter using tin coated copper ferrules and the cheapo ones using tin coated brass ones. Their point was that brass has more electrical resistance than copper.

Now, given you're connecting to brass screws/connectors in the sockets and consumer boxes, would using copper ferrules make any real difference? Also, since tin has even more resistance than brass, does adding a ferrule actually then help make a better connection?

 

[mikehammer69]

In distribution boards you've a better connection with panel flex shoved directly into terminal clamps

In large panels with lots of terminals you need crimps and ferrules for a tidy job

They do add another layer of resistance however small

 

[Lower]

Ferrules also increase the contact area between the copper and the terminal by stopping the copper from spreading so much under the pressure of the clamp.

 

[JohnW2]

Ferrules also increase the contact area between the copper and the terminal by stopping the copper from spreading so much under the pressure of the clamp.

That presumably depends to at least some extent on the nature of the clamp and the degree of squashing of the strands that occur -since I imagine that, under some circumstances, "the copper spreading" might actually increase the contact area (so that 'stopping the spreading' might actually reduce contact area)?

 

[mattylad]

One of the main advantages of cord end crimps/bootlace ferrules is that when used with trirated/fine strand wire there is a massive reduction in fine whiskers of wire that do not make their way into the terminal. This prevents accidental shorts (and the wire up the fingernail when you go to touch it).

The additional resistance is so small it is not worth worrying about unless you get into wiring resistive sensors and cabling, such as K-type cables - in this instance you are best not to use them.

Also makes refitting the wire into another terminal upon modifications etc. far better as the wire end is not chewed up.

 

[ericmark]

Main reason for ferrules was to hold the cable marking on the cable, without them the marking can fall off. I agree with @mattylad that strands can bind a screw thread, making it seem tight when it's not, normally you can feel something wrong when that happens, unless using a torque screwdriver, they take away the feel, and yes I am guilty of using electric screwdrivers with a torque setting, so you don't realise when a screw has a fault with it.

I have a lovely set of crimp pliers with exchangeable jaws. But for them to work, you need to use the right crimp with the right jaw, they look good, but I have found wrong crimp or jaw used, so maybe on average better not to use pin crimps?

 

[bernardgreen]

 

[Lower]

That presumably depends to at least some extent on the nature of the clamp and the degree of squashing of the strands that occur -since I imagine that, under some circumstances, "the copper spreading" might actually increase the contact area (so that 'stopping the spreading' might actually reduce contact area)?

I should have been more specific and said that the ferrule stops the strands from spreading, rather than the copper.

 

[JohnW2]

I should have been more specific and said that the ferrule stops the strands from spreading, rather than the copper.

Fair enough, but is it not the case that, in some cases, the spreading of strands will facilitate the spreading of copper within those strands (with a consequent potential increase in contact area)?

 

[mikehammer69]

Fair enough, but is it not the case that, in some cases, the spreading of strands will facilitate the spreading of copper within those strands (with a consequent potential increase in contact area)?

Say a 10 or a 16 panel flex under a mcb clamp

I dont see how you could have a better connection using a ferrule

As pointed out above they do secure the strands and facilitate better reworking of boards

Worth pointing out leaving loose strands would be very sloppy work