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Mundane discussion of DIN rail Terminal Blocks

Mundane discussion of DIN rail Terminal Blocks

Mundane discussion of DIN rail Terminal Blocks

(OP)
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?

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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.

RE: Mundane discussion of DIN rail Terminal Blocks

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-bin/cm_syb.exe?Startup=Viewer/catalog_show_info_simple&SessionID=sess3756975519377&Key=infoID&;Key=ID&Key=lang&Key=ObjectID&ObjectID=prod1248372409580&ID=group2884198853312&infoID=productDetails&lang=en&Refresh=false
 

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

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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.

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

>Just typical.. for a controls/instrumentation EE

sticks and stones . . . .

RE: Mundane discussion of DIN rail Terminal Blocks

lolpoke

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

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Mundane discussion of DIN rail Terminal Blocks

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?
 

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

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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.
 

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

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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.....

RE: Mundane discussion of DIN rail Terminal Blocks

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.lol

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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.

RE: Mundane discussion of DIN rail Terminal Blocks

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 smile. 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-bin/cm_syb.exe?Startup=Viewer/catalog_show_info_simple&Key=infoID&;Key=ID&Key=lang&Key=ObjectID&SessionID=sess4544531552389&infoID=groupInfo&ID=group3520462493849&;lang=en&ObjectID=&Refresh=false
 

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

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

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

RE: Mundane discussion of DIN rail Terminal Blocks

Hey Skogs; Do you have a link to a typical IDC you'd be referring to?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Mundane discussion of DIN rail Terminal Blocks

This is a typical one.

http://www.electusdistribution.com.au/images_uploaded/IDCconnE.pdf

I cannot say for sure if these are the good ones. What I have used and seen used are Berg, T&B, Cannon and other well-known brands. T&B may not be with us any more but their connectors still work.

This is what it looks like in the crane application:



Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Mundane discussion of DIN rail Terminal Blocks

Ha!  I use those by the case and always call them IDC!  

I thought you meant something else for point to point wiring.

I really like T&B's stuff.
Thanks.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Mundane discussion of DIN rail Terminal Blocks

(OP)
Keith,
These are the ones I was thinking of. The are individual blocks for DIN rail mount and require no special tools other than a screwdriver blade narrow enough to fit in the slot. Available from Phoenix, Entrelec, Wiedmuller also, maybe others.

IDC terminal blocks (note: PDF starts off at 154% view. Reduce the view size for easier scrolling)

RE: Mundane discussion of DIN rail Terminal Blocks

I have wagos by the gross throughout my plant. Lots of problems. Problems are related to the constatnt disconnecting and reconnecting of the wires because we test things to death. Particularly true on our engines. Not trying to stir that all up again. Just a numbers thing. The more times a wire is disconnected, the greater chance of it breaking, or a strand not making it in and shorting. HT wire seems to be the worst.

We don't use ferrules (thimbles) at all. How many of you do use them?

 Where we use spring clamp terminals on large power cables, we have no issue at all, but no one gets in to mess with those, and access is much better.

 I have a requirement that my equipment come with connectors complying with ANSI/UL 486A-1991. I don't know if these do, and I have never checked. Mostly because I don't want to know the answer I guess. Changing out tens of thousands of connectors doesn't sound like fun to me.

RE: Mundane discussion of DIN rail Terminal Blocks

rovineye; That pretty much concurs with Scotty's assessment. Sounds like if you want to regularly disconnect wires and reconnect them then both 'bare' wire solutions, spring, or cage, have a wear-an-tear issue.  Go with crimped on spades so you don't actually undue/re-due the wire connection, but rather, the 'once removed' circuit connection(spade).

Thanks jraef; looks like even less hassle than the standard spring ones!

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Mundane discussion of DIN rail Terminal Blocks

spring cage - wago's are too weak, never use them
spring cage - phoenix are a lot better
but spring cage has its drawbacks, You can clamp down on the insulation, even if you pull the wire to make sure.
If your using wires that have the nipple clamped on, spring cage can not bit into this metal nipple and hold it.
I believe it takes more time to to terminate spring cage then a screw terminal.

Screw terminal -  only drawback - have to retighten maybe every quarter or semi annually if you have a lot of vibration.

RE: Mundane discussion of DIN rail Terminal Blocks

From the production end of it, our guys love building systems with the spring clips. From the perspective of maintaining the equipment it is a different story.

Among the other things already mentioned, access to the spring-release notch is often difficult. In an industrial environment, I don't want my guys sticking both hands into the multiple wires coming from the terminal strip to pry open a spring clip- I'd rather they have better control over what they're touching by having straight-on access with an insulated screwdriver.

Unless there is significant thermal cycling or vibration, I typically specify screw terminals. The key to eliminating loose connections is to re-tighten them during a regular bi-annual P.M.

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