Spring PCB terminal block for stranded wire

Question

I am planning to use this spring terminal block:

Voltage and current requirements: 220 VAC 5 amps max

Wire type : Multi strand wire - 1 sq mm to 1.5 sq mm like this:

Datasheet says that I can use 0.2 sq mm to 2.5 sq mm:

I have never earlier used spring terminal blocks. Online reading suggested use of ferrules for multi strand wires in some articles but other articles and youtube videos were fine with directly stripping and inserting the stranded wires.

What is the preferred way to use such connectors with multi strand wires?

I used similar spring terminal blocks and didn't have a great experience. I'd suggest going for a terminal block with screws. They last longer and are much easier to use — Sachin, Jul 28 '17 at 09:43
@Sachin - can you please share link to the exact product that you chose? Can you further explain the issues that you faced? Thanks — Whiskeyjack, Jul 28 '17 at 09:47
I used the ones on the bottom left of this image: http://global.wago.com/media/catalog-media/group/00182046_0.jpg The issue with these was after sometime of usage, the springy buttons used to come out of the terminal block permanently, and they then had to be replaced — Sachin, Jul 28 '17 at 10:01
See my answer to https://electronics.stackexchange.com/questions/213996/is-a-screw-or-push-in-terminal-better-for-vibrating-environment/214019#214019. I reckon that in a cage clamp ferrules give a reduced contact area compared to squashed strands. See the photo in the link. — Transistor, Jul 28 '17 at 10:11
@Sachin - Thanks for the link and your update. I want to know - did they come out due to repeated use or did they come out just like that during sitting period? In my use case, they won't be used repeatedly - putting the wire in, pulling them out. I want to know if that is a variable in your failure case. — Whiskeyjack, Jul 28 '17 at 10:31
@Transistor - Thanks for the link. Looks like I can go ahead without using a ferrule. However I want to know whether I can consider the spring terminal that I showed as a cage clamp or does mine won't qualify as a cage clamp. Please help. — Whiskeyjack, Jul 28 '17 at 10:33
They were used repeatedly, (though not too many times)but the way the spring was connected to the terminal block, it was always fragile. So if you go ahead with these, be gentle with them — Sachin, Jul 28 '17 at 10:35
@Whiskeyjack: There isn't enough detail in the datasheet to see the clamp mechanism. I can't help. — Transistor, Jul 28 '17 at 10:37
Why not just tin the ends of the stranded wires with a little bit of solder before inserting them into the spring connectors? It will keep the strands together like a solid wire and will not increase the diameter significantly. — Brian Rogers, Jul 28 '17 at 15:32
@BrianRogers - Operations will get difficult. When you have to get a job done in field by people who aren't very educated or who are in a hurry - they are bound to cut corners every now and then. Tinning each wire will take more time and machinery. Hence I want to give a dumb proof solution which is comfortable for the workers in field. — Whiskeyjack, Jul 28 '17 at 16:21
@Whiskeyjack I see. You should state these requirements in the question then. Your question doesn't provide context that this is a field environment versus a one-off project. — Brian Rogers, Jul 28 '17 at 16:30

score 5 · Accepted Answer · edited Jul 28 '17 at 10:53

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Of course ferrules like these --> Ferrules are always good for such terminal blocks but they are not mandatory.

Depending on the thickness of the used wires, it can become very hard and ugly to place them in the terminals.

If you have them, use them but as I said they are not mandatory

edited Jul 28 '17 at 10:53

Sachin

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answered Jul 28 '17 at 09:45

S.G

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Placing the ferrule crimped wire seemed to be the only problem because they essentially increase the wire's neck dia. Placing two wires adjacent to each other will be a pain if I put ferrules on them. – Whiskeyjack Jul 28 '17 at 09:48
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you mean because of the plastic insulator? normally it is flexible and it will give in, so it is no big deal – S.G Jul 28 '17 at 10:31
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Much of what I do is to come up with ways to produce assemblies faster, cheaper, and more reliably. Ferrules help in this regard in that they keep all of the strands together, preventing shorts. It also makes inspection and reconfiguration much more reliable. I would suggest: One ferrule per spring clamp. If you need 2 wires, put 2 wires in the ferrule and crimp. The reliability of the spring clamp should be a function of the clamp manufacturer, not the presence of the ferrule. We use them often, and are very pleased. Investigate the terminal block quality, and go from there. – Chris Knudsen Jul 28 '17 at 11:56

score 2 · Answer 2 · answered Jul 28 '17 at 11:19

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In my case I prefer using a terminal on the wire when I used it with a spring terminal block. This way it holds the wire better and the wire doesn't get loose so easily.

A normal terminal like this one is ok:

enter link description here

answered Jul 28 '17 at 11:19

Dimitri

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sorry, left the PC for a while and didn't see the answer. was already there. – Dimitri Jul 28 '17 at 11:20

score 2 · Answer 3 · answered Jul 28 '17 at 15:40

I'm a really big fan of screw terminal blocks for similar reasons to what have already been written. But regarding this spring terminal block, I'd only ever use ferrules with it. Issue is you could go over the 2.5 sq mm, however leaving them all frayed like that is really not in your best interest. It introduces safety issues and random shorts can happen.

If you really don't want to use ferrules I'd recommend twisting the wires to keep them neat and organized (see picture). It's a little safer than just pressing them in frayed like that but still not ideal.

score 2 · Answer 4 · answered Jul 28 '17 at 16:57

For these I always use ferrules, because the spacing is close and these bend the wire if you don't. If you don't use ferrules by the second or third time you use a wire in one of these even a twisted end has frayed and is prone to shorting to the adjacent terminal. The core issue is not that it is a spring clip but that your wire spacing is small. Just always use crimps or ferrules or solder. etc. when you have closely spaced stranded wire.

Spring PCB terminal block for stranded wire

4 Answers4