Panel terminal block buses

On our panels, we use jumpers to tie several terminal blocks together to create a "bus" . IE. 24vdc+ digital, 24vdc- digital, 24vdc+ analog, 24vdc- analog, etc.

A couple questions.
1. When doing this, how do you prefer numbering the terminal blocks? I think it is nice to have all blocks of 1 bus the same number. Example TB1-1 is all24vdc+ digital, TB1-2 is all 24vdc- digital, etc. This does create a pain when it comes to terminal block numbers, you end up buying a bunch of extra number sheets to get all of the 1's and 2's. Does anyone else do it this way?

2. Another option is individual numbers, Ex. TB1-1,2,3,4,5 is 24vdc+, TB1-6,7,8,9,10 is 24vdc-. If using terminal block jumpers, this would mean potentially two wires per block. On your drawing would you list TB1-3 two times for two different pieces? What's everyones preference?

g.mccormick said:

On our panels, we use jumpers to tie several terminal blocks together to create a "bus" . IE. 24vdc+ digital, 24vdc- digital, 24vdc+ analog, 24vdc- analog, etc.

A couple questions.
1. When doing this, how do you prefer numbering the terminal blocks? I think it is nice to have all blocks of 1 bus the same number. Example TB1-1 is all24vdc+ digital, TB1-2 is all 24vdc- digital, etc. This does create a pain when it comes to terminal block numbers, you end up buying a bunch of extra number sheets to get all of the 1's and 2's. Does anyone else do it this way?

2. Another option is individual numbers, Ex. TB1-1,2,3,4,5 is 24vdc+, TB1-6,7,8,9,10 is 24vdc-. If using terminal block jumpers, this would mean potentially two wires per block. On your drawing would you list TB1-3 two times for two different pieces? What's everyones preference?

Click to expand...

We use PDX, where PD means Power Distribution , and X is the # of the block.

Internal DC
PD1+24V is 24VDC + on power distribution block #1
PD1 Com is 24VDC common on power distribution block #1

External DC
PD2+24V is 24VDC + on power distribution block #2
PD2 Com is 24VDC common on power distribution block #2

etc

...you end up buying a bunch of extra number sheets to get all of the 1's and 2's. Does anyone else do it this way?

Click to expand...

It may be time to buy a label printer, and make your own stick-on labels, as many as you need of each number.

Overall, I think it best not to have a bunch of different numbers for your power supply wires. That makes trouble-shooting more difficult. At a remote device or another box, you could never be sure that you were looking at a power supply wire from your panel, or something else.

Lancie1 said:

It may be time to buy a label printer, and make your own stick-on labels, as many as you need of each number.

Overall, I think it best not to have a bunch of different numbers for your power supply wires. That makes trouble-shooting more difficult. You could never be sure that you were looking at incoming power, or not.

Click to expand...

We have a label printer. We print labels for all of the wires, I'm not a huge fan of them for terminal blocks. Atleast not printing numbers and attaching to the "chiclets" terminal block tags.

I would like to get a terminal block tag printer. The ones that I have seen are a little salty though.

I do like the ease of having common terminal block numbers for buses, makes troubleshooting easier as you said.

In general, all points that are electrically the same (share the same node on the schematic diagram) should have the same basic wire number. The number should only change when there is an electrical device between two nodes.

It may not be possible to always make the terminal block number the same as the schematic wire number. That is nice if you can get it. For me, the wire number is more important. Terminal numbers may get changed, but the wire number should be related to the function of the wire and should change less often.

Lancie1 said:

In general, all points that are electrically the same (share the same node on the schematic diagram) should have the same basic wire number. The number should only change when there is an electrical device between two nodes.

It may not be possible to always make the terminal block number the same as the schematic wire number. That is nice if you can get it. For me, the wire number is more important. Terminal numbers may get changed, but the wire number should be related to the function of the wire and should change less often.

Click to expand...

Yes wire numbers stay the same accross termnal blocks, and all on a bus would be the same. They pick up the number from the schematics ex. 11021 (sheet 11, row 2, first wire) is 24vdc+ digital on this current schematic I am working on. All 24vdc+ digital is 11021 unless it is modified, example being going through a NO contact of a relay. The 11021 all go/originate from TB2-1. There are many TB2-1 terminal blocks, but they are jumpered together.

Generally the people who work on this stuff in the field prefer that a terminal number be the same as the wire number landed on it. Think about what would happen if a wire fell off the terminal.

The machine goes down, the electrician or tech opens the panel and sees a wire has fallen off. If the terminal label and wire labels are the same, this is a 10-15 second fix. If they are not, then you are assuming (and we all know what happens when you do that!) that the documentation will always be complete, accurate, and readily available. At the absolute minimum, a 10-15 second repair becomes a 2-3 minute repair, longer if the drawings are not readily available, and that particular circuit is not quickly found in the drawing set. In a manufacturing environment, time is money. So think about it this way, if you don't match the terminals to the wire numbers, you are unnecessarily adding (albeit a small amount of) expense to the lifecycle of the machine.

You'll see a lot especially in IEC panels that terminal strips are treated as devices unto themselves, and will have their own designation on the schematics like "X1," "X2", etc. For some reason, Europeans really don't like wire numbers. I've seen a number of IEC panels from European manufacturers where the wires aren't labeled at all, and any troubleshooting is completely dependent on having the documentation, which is rarely in English. Basically, these panels aren't build to be fixed. They are built so that you spend major bucks on the manufacturer's service tech when the machine breaks down. Anyway, back to what I was saying. I've seen a few Euro panels where the wires are labeled, but actually have different labels each end that are in the format of deviceid:terminal. So a wire landed on Terminal Strip X1, Terminal 5 will be labeled X1:5 while the other end would be a device like A1.3:X2 or something. That would solve the "what if a wire falls off?" problem while still allowing you to be all fancy and Euro with your panel design. ;-P

WE do it like this, the block is TB1 and each individual terminal is marked up with it,s own number, for instance 1,2,3,4,5,,6,7,8,9... and so on, then on the drawings we have each cable has a label attached with the TB number and the individual terminal number.... TB1- 5 so much easier when trouble shooting and trying to trace cabling in panels with cables all the same colour...

I use a different color terminal block for the "buses " Blue for 24VDC, red for 120VAC, white for neutral and yellow for outside sourced.
It draws your eyes to the different blocks so you know where to put the other lead of the meter.

I mostly build small panels, and I use triple-level feed-thru terminal blocks for all my field inputs. The bottom two levels are my DC bus, which serves two purposes. On the field side, every sensor has a place to connect its + and -. On the panel side, this gives me a bunch of + and - terminals, so I don't have to daisy-chain components.

To label the terminals, I just use a fat sharpie to color the marking strip before I install it. I use brown for + and blue for - since that's the color code for most cordsets.



-Eric

I have found it best to use the wire number for the terminal number, and all electrically identical wires should carry the same number. If all terminals come from a power supply output they should all have the same number. After all, if they are all directly connected, they are the same and are interchangeable, right?