Ferrules use on stranded wire

richard5933 · June 09, 2019, 04:15:47 AM

When I ran the new cables from the shore power inlet to the transfer switch, I noticed that the originals all were installed using crimped ferrules before inserting into the screw-down terminals.

I was using fine strand wire, and the research I did showed that it was a good idea. Seems to be much more common in the UK than around the US.

It added an extra step, but sure makes for a neater job. Also, I don't see any of the damage to the individual strands normally seen when inserting fine strand cable into the screw-down terminals.

What are others doing out there? Anyone else crimping on ferrules?

bevans6 · June 09, 2019, 04:49:20 AM

I do. I was taught, in technical school for electronics, to terminate fine stranded wire with a crimped terminal for plain screw terminals. Only solid wire under screws directly. I don't actually know the code on it for power use, though. Lots of screw terminal devices are designed for stranded wire, and they tend to have wire capturing devices or toothed washers so that the wire is not being pulled and pushed by the screw directly (key word - "directly"). The device will be listed and the paper it comes with will say if it's compatible with stranded wire. If you twist the stranded wire counter-clockwise it tends to self-tighten as the screw clamps it.

buswarrior · June 09, 2019, 05:43:03 AM

The marine folks properly terminate wire with crimp terminals.

The ABYC standards evolved via science, copied by the aviation field, past misadventure is investigated and standards evolve to prevent re-occurrence.

"Never Again" or in our case "Ain't gonna be me..."

Vibration and harsh environmental/atmospheric conditions in a boat, not so much different in a coach. If anything, a coach will see harsher vibration than a boat. Vibration is deadly on wiring connections.

Typical RV wiring methods are dangerous garbage in comparison.

Protect the wires, enjoy long reliable and safe electrical system.

Happy coaching!
Buswarrior

chessie4905 · June 09, 2019, 06:12:02 AM

https://www.amazon.com/30-030-Noalox-Anti-Oxidant-Compound-Squeeze/dp/B000LDE7V4?ref=silk_at_search

windtrader · June 09, 2019, 09:09:18 PM

Having some experience in past lives with cable terminations, one common best practice is to crimp the raw wire directly to the terminal connector. This ensures the most direct metal-metal contact and minimizes electrical flow disruptions such as having solder between the wire and terminal.

richard5933 · June 10, 2019, 03:40:18 AM

Quote from: windtrader on June 09, 2019, 09:09:18 PM
Having some experience in past lives with cable terminations, one common best practice is to crimp the raw wire directly to the terminal connector. This ensures the most direct metal-metal contact and minimizes electrical flow disruptions such as having solder between the wire and terminal.

For crimp terminals I agree - crimp the terminal directly to the bare stranded wire end. In this situation I'm really talking about when a stranded wire needs to be connected to something like a manual transfer switch which uses a screw-down terminal clamp. Sometimes when you tighten the screw, the strands in the wire spread out and the clamping action doesn't seem to grab all the wires, no matter how well they are twisted together.

The crimp-on ferrules can be applied with either a 6-sided or 4-sided crimp tool, and which to use depends on if the screw-down terminal has a round or square opening. I'll try and get some photos taken later with some surplus parts to show what I installed.

Jim Blackwood · June 10, 2019, 07:05:31 AM

Best practice would be to use an uninsulated ring terminal with a hydraulic crimper and then apply sealant lined heat shrink tubing. The hydraulic crimper compresses the ferrule and wire to the point where all air is removed and creates a solid metal piece. Better still, dip the wire end in anti-oxidant compound first. Then the sleeve reinforces the mechanical bond and keeps the air out. Some would recommend sealing the terminal end of the ferrule with a solder cap as well but that's an older practice and risks getting solder wicked through the ferrule where it can embrittle the wire. Extreme? Yes indeed. (Hydraulic crimpers are not cheap.) But also extremely reliable.

Jim

richard5933 · June 10, 2019, 09:21:25 AM

Quote from: Jim Blackwood on June 10, 2019, 07:05:31 AM
Best practice would be to use an uninsulated ring terminal with a hydraulic crimper and then apply sealant lined heat shrink tubing. ....

Jim

For ring terminals, for battery cables, etc. I agree. However, the kind of terminals I'm talking about are not ring terminals or battery cables.

Here are a few photos to help. The first is the transfer switch itself. You can see the stranded wire is inserted directly into the terminals which clamp onto the wire when the screw is tightened. The wires shown are the remaining original ones, and you can see the ferrules wrapped around the stranded wire.

The second photo shows one end of the cable I removed. In spite of the insulation cracking, the ferrules are still in place keeping the strands of the wire neatly in place. (The insulation was in place when I removed it - it cracked and fell apart the first time I flexed the cable.)

Next to the original cable is an example of the crimped ferrule I used on the new stranded wire. The ferrule itself is actually quite soft and allows the screw clamp in the terminal to compress it slightly to ensure a firm hold is attained. It keeps the fine strands of the cable from being pushed away from the clamping portion of the terminal as pressure is applied by tightening the screw.

The third photo is another example of where the crimped ferrules could be used. This is an old 30-amp receptacle/inlet. The stranded wire is inserted through the three color-coded openings on the end, and the screws on the side are tightened to clamp down on the wire.

Hope this helps.

Jim Blackwood · June 10, 2019, 11:54:21 AM

The integrity of the connection depends entirely on the crimping method, which in the main depends on the force applied to the ferrule. Whether square or round, the new standard for a crimp is to make the ferule one with the wire, which is best done hydraulically, regardless of the wire size, with force applied from all sides, 4 or 6 being the most common. Actually it isn't really that new of a standard, the USAF was using 4 sided mechanical crimpers for the contacts of multipin connectors over 60 years ago, but the hydraulic ones can give a more uniform crimp.

In general though, the problem is that without the ferrule individual strands can get sliced off and deformed unless the terminal is very well designed and even then strands tend to escape, whereas proper fitting of a ferrule is difficult. Solder improves the contact but can cause embrittlement of the wire. One solution might be to use uninsulated butt splices, properly crimped and insulated, and insert the other end into the connector but that's really almost the same as a ferrule only longer. Every time you add another element you introduce another potential failure point. Sometimes you just have to take your best shot and hope it's good enough. In those cases I like to use a liberal dose of anti-corrosion gel as added insurance.

For thinwall ferrules that depend mostly on the clamping force of the screw in the connector, well at least the wires don't get away, but there's no way that screw is going to develop adequate force.

Jim

Geoff · June 10, 2019, 04:43:34 PM

Did anyone suggest silver solder? I couldn't get through all the posts.

richard5933 · June 10, 2019, 05:37:26 PM

Quote from: Geoff on June 10, 2019, 04:43:34 PM
Did anyone suggest silver solder? I couldn't get through all the posts.

Not yet, but not sure if it would be any better. What are your thoughts?

Iceni John · June 10, 2019, 07:05:07 PM

When I rebuilt my 100 amp fuse holder and replaced its 4AWG cables, I used small copper tubes from Home Despot, I think intended for plumbing, and crimped them on with my cheapo hydraulic crimper. It made perfect hexagonal ferrules on the ends of the cables for the pinch screws to dig into for a good connection, cost only cents and works great. That crimper tool is pretty useless for larger crimps such as on 2/0 and 4/0 lugs, but for the little stuff it's fine. For the big 'uns I use my FTZ 94284 circumferential crimper that works very well, but it doesn't do so well for the smaller sizes.

John

richard5933 · June 10, 2019, 07:10:25 PM

I wonder what the functional difference is between using the thicker/stronger ferrules that require hydraulic crimpers and the softer ones I used which can easily be crimped by a hand crimper (4 or 6 sided)?

The copper tubes just mentioned with a hydraulic crimper would make a more stout end to the cable, and the set-screw will have something stiff to go against. But, the softer ferrule will deform slightly and better take the shape of the terminal it's being clamping into providing more surface area of contact.

chessie4905 · June 11, 2019, 03:40:27 AM

Thinner ones could "spring back" a little compared to heavier ones. Can the screw supply adequate pressure to arrive at a secure connection. I think I prefer soldered ends to clamp upon with contact paste. Since the wire is additionally clamped about 2 inches away, I can't see any failures from flexing. But, do it your way and report back in 5 years. Either way, wouldn't be a bad idea to check screw tightness once in a while, or use an iron gun.

Jim Blackwood · June 11, 2019, 08:00:51 AM

The difference is in the pressure that is applied. A hydraulic crimper can apply so much force that the wire is literally pressure welded to the ferrule and between the strands, making one solid piece. If you try to remove the ferrule it's like cutting solid billet almost. A hand crimper is never going to achieve that no matter how good it is, and obviously a grub screw can't even get close.

Jim