Mundane discussion of DIN rail Terminal Blocks

[jraef]

I would like to hear people's impressions on the subject of "Spring Clamp" style terminal blocks vs "Screw / Box Clamp" style, as well as "Insulation Displacement" style for mounting on to DIN rail. Here on the West Coast (USA), I know of nobody who likes or uses the spring-clamp style, nor the insulation displacement style. Everyone wants and uses the screw clamp style terminals.

The general verdict around here on spring clamps is that they are difficult to use if you do not have the exact screwdriver it takes to open them. They fear that sooner or later someone will attempt to make a change with the wrong tool and damage the block. There is also a general distrust of the long term reliability, even though the data from IEC users is that they are MORE reliable than screw clamp types. I tried some Wago spring clamp blocks a while ago and I had the entire project rejected by Boeing as being unsuitable for their environment until I changed out all 2000 terminal blocks to screw clamp style.

As to insulation displacement styles, these are relatively new around here and the mistrust runs deeper. People tend to associate them with the cheap lamp plugs that you stab on through the insulation of Zip cord, so they don't want to trust anything industrial to that kind of technology.

Comments or opinions?

 

[itsmoked]

Hey, heY, HEY!

I use them! I will use only them unless I am ordered to use the ancient, decrepit, old fashion, archaic, problematic, screw terminals; box, or otherwise.

I love them and the easy color coding they allow.

Absolutely you need a proper screwdriver. I solve that by tethering one onto the project after I deliver it.

Insulation displacement? Not my cuppa tea.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[catserveng]

We prefer them for recip engine and generator mounted controls. Much fewer problems with wire compression and subsequent intermittant problems. Screw terminal type blocks have been around a long time, but we have as many installation problems with contractors with them that we do with the spring clamp type. In a lot of the jobs we ship, we send a couple of the right size screwdriver with them, for $20 saves a lot of grief.

We have not had good enough success with the insulation displacement style to justify the cost as of yet, too many insulation systems they don't seem to work well on, at least in our experience.

I probably spend 80-100 hours a year chasing problems caused by screw type terminal blocks, usually improper torque, wire loosening, or vibration damage in our market. To date have had very few problems with spring type blocks from reputable manufacturers. Have had one "lower cost brand" actually cut the wire like a shear, but other than that we are pretty much sold on using spring clamps from now on.

Hope that helps.

 

[ScottyUK]

I hate the spring type. They are the work of Satan.

The old screw type, when used with an appropriate compression lug, are far superior for anything whichy might need to be dismantled for maintenance or fault-finding. The spring type are great for OEMs because they are cheap and quick but once in the field they are a liability.

By far the best terminal blocks for anywhere involving vibration or protection circuits where you just can't have the connection come loose is the old RSF series of blocks made by Weidmuller to a CEGB specification. These use a spring within a rising clamp style block to positively clamp onto a compression lug with a small lip which engages with the terminal. A conventional screw provides primary clamping force, but should it come loose the spring will maintain contact pressure.

http://catalog.weidmueller.com/cgi-...2&infoID=productDetails&lang=en&Refresh=false

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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

Typical...
Just typical.. for a controls/instrumentation EE.

Always wanting to unhook things so they can get at them with their Ohmmeters and what-not.

Hmmm.. some british band had a song about instrumentation engineers:

I'm your wicked Uncle Ernie
I'm glad you won't see or hear me
As I fiddle about
Fiddle about
Fiddle about!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rbulsara]

I am not sure how many varieties of spring clamp type terminals. But one very conservative yet top quality custom switchgear and controls manufacturer in the USA , whose judgement I trust, were always fan of ring terminals with screw terminal strips. However, recently they have adopted Wago's Cage Clamp type terminals and they claim that they are equally good or better as the screw type. Saves labor. Although requires a special tool.

So only spring clamp I would use is that..I am not the personal user or installer..but a consulting engineer. So take my opinion accordingly.

 

[davidbeach]

I wouldn't trust anything other than ring terminals for CT circuits.

 

[danw2]

>Just typical.. for a controls/instrumentation EE

sticks and stones . . . .

 

[itsmoked]

I wonder what happened to Scotty? I figured he'd hit back quickly...

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Hi Keith,

I've been in counselling sfter being called an instrumentation guy, but I'm feeling well enough to speak to you now!

Anyway, those spring terminals are relatively easy to dismantle, but they chew the core up so badly that putting it back together again is difficult. And it is nigh on impossible to use fine multi-strand wire and be sure that all the conductors are in the clamp. Some of them end up pressed back. With solid core conductors they 'vee' the copper and make a weak spot which fractures after a few assemble-dismantle cycles.

Those terminals are a symptom of the engineering philosophy brought in by the accountants and technophobic MBAs when they took over: everything is now built down to a price, instead of being built up to a standard. Supposedly this is progress?


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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

Hi Scotty!

I wondered where you got off to.. Thought maybe you'd lost your screwdriver. LOL

What's wrong with instrumentation? I would figure without it a power-plant just becomes a plant.. where metal things compost. Is there a negative connotation associated with 'instrumentation'?

I still prefer these wago springs but you raise an excellent point I hadn't thought of. That being one having to open connections to check an instrument, etc. The spring dealies just return a bare wire ready to splay rather than a spade that's easy to clip to.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Just the age-old rivalry between the 'E' and the 'I' boys, that's all. Both have their place. Where I work the metal things compost anyway because of the local environmental conditions.


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Sometimes I only open my mouth to swap feet...

 

[pooslinger]

I make a really good living repairing the mistakes of the designer. I could give my two cents but I would only be repeating what scotty already said. Check out the link below, Dilbert pretty much sums up this whole conversation.

http://www.youtube.com/watch?v=ySpOuaYwLQU

 

[ILCML]

I don't like the spring clamp style because they seem to depend on the strength of the spring. When you screw down the box style on a wire, you know it's tight, and if you're not comfortable with whether you've got the wire or the insulation, you can pull it out and it's very clear what got clamped.
Also, I've used products with the spring clamps that where the entire product is as light as a pencil, and finding way to insert the wire and then hold it while pushing down on the spring clamp is next to impossible...
The insulation displacements are nice if you have the tool, but......you need the tool.....

 

[itsmoked]

ILCML; I don't get it.. You insert a wire into a spring clamp and then pull on it. Doesn't come out.. It's not going to fall out. I know it's tight. Course with vibration/thermal cycling my screws could get loose.(Yes I know you think my screws are already loose.)

Your latter example is pretty funny though. I can just see that. Holding a wire, a screwdriver, the box is trying to get away. Like grabbing a fish on a line.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ILCML]

I guess it depends on the location.....and who's poking around etc...obviously it's not just going to fall out

 

[ozmosis]

We generally use spring clamp terminals on our VFD control board. Some of the latest drives do have screw terminals but this is because we have removable (pluggable) terminal strips and you cannot (seem to) get spring clamps on removable terminal blocks.
Having had sping clamps on our drives for a number of years, there are few comments against them once people are familiar. They hold the cable well. One downside is where more than one cable with bootlace ferrules are fitted then you can get a lopsided face and one of the cables could work loose. In the main most folk are ok.
Screw terminals are ok as well until you get superman trying to tighten the screws and suddenly stripping the thread. Then you are goosed.
I think it is 6 of one and half a dozen of the other.

 

[ScottyUK]

Hi Sed2,

They are available, although I'm not sure why I'm telling you - you might start using the damned things and I'll have to buy drives from ABB instead . At least if they are two-part connectors I can throw away the spring part and replace it with a screw type! Here's one example from Weidmuller:

http://catalog.weidmueller.com/cgi-...3520462493849&lang=en&ObjectID=&Refresh=false

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Sometimes I only open my mouth to swap feet...

 

[ozmosis]

Thanks Scotty. Those darned HW development guys, always the easy option....
However, I'll pass on the threat of ABB to make them think about future developments!
cheers

 

[Skogsgurra]

Not much said about IDC here.

I said "NO - not on my watch!" when I saw them a few decades ago. And now, I just love them. They are really gas-tight. And that objection about tools - don't understand. Do you not use proper tools for other work? Why not for connectors?

I have just visited an old (installed 1986) drive. Dirty, hot, vibrations, dust, gases. An overhead crane transporting molten steel. I got pictures. Looks terrible. But the problem was NOT with the IDCs - it was in one of those screw terminal pluggable connectors.

Have same experience with ribbon cables and IDC in pulp and paper and also sewage works. A well-known corrosion test for connectors. Equipment run after thirty years. No problems that I know about.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...