In another web forum I follow, someone has suggesting that tinning heavy duty stranded cables prior to use in a grub screw connector is a good idea. (In this case, for a 12V DC supply to an inverter)
I'm pretty sure that this is a bad idea (due to plastic deformation of solder and joint overheating) but it would be nice to have a web link to a site that gives definitive info. Can anyone help?
Tim
Practical experience says, definitely don't do this. If you do, when you check it a year later the screw is loose.
There's nothing worse than having a screw loose.
Bill
The reason it's done is to stop the strands from separating under the grub screw. Considered good practice, especially if the cable is small and the treminal hole is big.
The reason it's done is to stop the strands from separating under the grub screw. Considered good practice, especially if the cable is small and the treminal hole is big.
The reason it's done is to stop the strands from separating under the grub screw. Considered good practice, especially if the cable is small and the treminal hole is big.
Wouldn't a ferrule be a better answer?
My dad. He's dead now. But he was an electrical engineer (power distribution). He has always been adamant that you never tin stranded cable prior to making a screw connection for exactly your stated reason (solder creeps).
Yes - I re-ferruled the fly leads on my RCBOs as I wanted to trim them to fit the CU rather than have miles of wiggly cables stuffed in there.
In the days before they supplied moulded on 13A plugs on appliances, the ba re ends of the mains leads were often tinned and people thought this was th e right thing to do. However, the tinning was applied only to make testing easier and most decent manufacturers recommended removing the tinned portio ns in their connection instructions.
Richard
On 07 Jun 2014, Bill Wright grunted:
I beg to differ.
It's having a wet-nosed Labrador dive under your dressing gown to give your naked arse a quick check, as happened to me 5 minutes ago
harryagain used his keyboard to write :
No, sorry, very bad practise. The solder migrates and the terminal screw will loosen, which is why manufacturers stopped doing it. The correct way is a brass furrel.
It's not and never has been considered good practice. Where you have a large terminal and a small cable you use a ferrule to prevent the strands spreading. But for high current use I'd expect the cable to match the terminal.
Too much info !!
Agreed. Copper doesn't creep despite being fairly ductile.
Solder does creep, so that after pressure the solder component will creep loosening the terminal leading to all manner of problems like an overheating joint.
Saying something 3 times does make the worst advice any more correct.
If no ferrule then the OP can strip more copper wire and double or even treble to fill the available space in the terminal.
I thought this was a good idea. it used to be done on all mains cables, and as long as you keep the screw checked over time where is the problem at least it stops strands wandering off and creating a hot spot on the other strands or shorting something out. Brian
There speaks the voice of experience. I have often been accused of this myself. Brian
My understanding too. What puzzles me, however, is how pretty much all of the accessory connections in my house that I have worked on or checked have been 'a bit loose' even though none of them is tinned. The place was re-wired profesionally before my time but long enough ago that all the cables are stranded. I assume it was a cheap job as many of the sockets are on the surface and there's a good bit of trunking around the place but either the bloke who did it just couldn't be arsed to tighten the screws or they have eased loose over the years.
Sorry, but completely wrong!
You must never tin strands together into a screw terminal - solder won't support the clamping force without creaping and losing contact pressure. A bootlace ferrule is the right solution, unless the terminal is designed to take stranded conductors.
The confusion arose during the era when appliances were supplied without plugs fitted on the leads. The leads were often stripped and tinned, but this was done to enable testing on the production line without a plug on the lead, and the tinning was to prevent injury to operators by getting a conductor strand stabbing them. The tinned ends must always be cut off before putting the wires into a terminal.
En el artículo , Harry Bloomfield escribió:
Ferrule is how it's spelt. And it should be crimped onto the strands
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