How to Number Terminal Blocks

Tim Ganz · Mar 25, 2014

I have seen terminal blocks labeled 1-200 or similar and I have seen them labeled with the same number as the wire in the terminal. What is the correct way? And why 2 different methods?

James Mcquade · Mar 25, 2014

Tim,

i have seen the terminals labled corresponding to the wire number - easier to deal with. there can be nultiple terminals with the same number, a jumper wire or shotring bar is used to connect the terminals.

i have also seen the terminals labled X-xxx where X is the terminal block number/letter and xxx is the terminal itself.
this mostly comes fro large OEM's who mass produce.

i always try to use the wire number approach. its easier on maintenance.

regards,
james

MikeW · Mar 25, 2014

Correct is whatever works for you: Does your customer/ company require it a certain way? If so, you are tied to their requirements.

I'm not constrained by any convention, I have always used #TX-??? where # is the enclosure number, X is the terminal blockset in the enclosure (if there are more than one set of terminal blocks) and ??? are terminals 1 - however many are needed plus a few for expansion if that is a possibility for a given project. YMMV, the main thing in my mind is to be consistent as you can be so that those that follow after you do not have to learn a new system for each new project. This convention helps when reading a schematic that has wires going to numerous locations.

Fitz · Mar 25, 2014

To me, the terminal number should be the wire number. Anything else seems to only add confusion. Keep it simple where you can, there are plenty of non-simple things we must deal with.

Tim Ganz · Mar 25, 2014

We have one machine where there are about 70 terminals labeled 209 and 209 is the +24 DC that goes to all field sensors and then from each sensor to the plc that wire is labeled with the PLC input #.

When we have a crushed conduit or similar and the fuse for 209 clears we can find the short but then we don't know what device that specific 209 wire is feeding so we have to remove Panduit covers and start tugging the wire to see where it goes.

Seems like the numbering 1-70 for example we could look at the print and see the field device fed from 209 on that terminal.

It seems because of this the sequential numbering being different from the wire number may be better or am I missing something?

Fitz · Mar 25, 2014

I see your point. How about 209-1, 209-2, etc?

dogleg43 · Mar 25, 2014

Fitz said:
To me, the terminal number should be the wire number. Anything else seems to only add confusion. Keep it simple where you can, there are plenty of non-simple things we must deal with.

Several years ago it was easier to put the wire number on the terminal number and then everything matched. Since the smaller IEC terminals have become so popular it is more difficult to do the same.

I now just show wire # xxxxxxxxx landing on terminal TB5-7 (terminal 7 of terminal strip 5, don't ask me why it's TB instead of TS, just tradition I guess).

If we are using multi-level terminals then then TB5-7's top level terminal may just be a square box, TB5-7's middle level terminal is a square box with a diagonal line thru it.

May not be perfect but it works for most situations.

Fitz · Mar 25, 2014

As MikeW said above, whatever works for you. I can see where you may not be able to fit a long number on the new smaller TB's, even if you have a TB marker printer. Large systems can have some long numbers.

jdbrandt · Mar 25, 2014

MikeW said:
Correct is whatever works for you: Does your customer/ company require it a certain way? If so, you are tied to their requirements.

I'm not constrained by any convention, I have always used #TX-??? where # is the enclosure number, X is the terminal blockset in the enclosure (if there are more than one set of terminal blocks) and ??? are terminals 1 - however many are needed plus a few for expansion if that is a possibility for a given project. YMMV, the main thing in my mind is to be consistent as you can be so that those that follow after you do not have to learn a new system for each new project. This convention helps when reading a schematic that has wires going to numerous locations.

Mike, I have seen designers who append the "source cabinet" number to every wire number that leaves the panel. So, wire number 9480+971 would be originating in panel number 971. It makes it easy to find the power in a multi-panel job, where there are interlocks, and such.
The OP's problem is not a terminal block problem...it is a design problem. The designer should have added some supplementary protection when fanning out power to many places like that, IMHO.

pal · Mar 25, 2014

As others have said - what your customer wants.
Personally I now use The Terminal block system . 2 advantages not so far mentioned -
1 The cores of multi-core cables align with the terminal numbers
2 With electrical CAD drawings an easily generated cross reference to the terminal block gives not only the wire , but the destination as well and ties to the cable reference.
Paul

califflash · Mar 26, 2014

I utilize the Tx-y system. Where x is the terminal strip and y is the location on the strip. For multi circuit blocks I append the end with a letter to represent what circuit the wire should land on. I went to this system because we use pre-printed labels. The quantity and variety of labels I needed was getting a little out of hand. Now I can use 0-100 and a-d to label and entire panel.

I also prefer to have my wire numbers reference the line number on the drawings instead of the termination point.

allscott · Mar 26, 2014

jdbrandt said:
Mike, I have seen designers who append the "source cabinet" number to every wire number that leaves the panel. So, wire number 9480+971 would be originating in panel number 971. It makes it easy to find the power in a multi-panel job, where there are interlocks, and such.
The OP's problem is not a terminal block problem...it is a design problem. The designer should have added some supplementary protection when fanning out power to many places like that, IMHO.

No kidding. Unfortunately it is far too common on machines that I see. I have one that right now is periodically doing something similar except it's not a dead short, just enough to drop the 24V to the entire machine for a split second (which in turn drops out the drives). I've been up and down that machine with a fine tooth comb looking for something but haven't found it yet, very maddening.

As far as an opinion for the OP I like labeling the terminals with the wire number if that is practical. And for the love of all that is holy do not skimp out and not label the wires just because you have a drawing showing what number terminal they should be on in the block.

How to Number Terminal Blocks

Tim Ganz

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James Mcquade

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MikeW

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Fitz

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Tim Ganz

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Fitz

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dogleg43

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Fitz

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jdbrandt

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pal

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califflash

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allscott

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