# Understanding DIN terminal block current ratings

I am making a control box for 12V 5 DC motors (~1.5 A total) and LED panels (~30 A). The system will pull ~30-35 A when it is running. Upon hearing of my project, a friend gave me some Allen Bradley 1492-J3 terminal blocks. I asked about the current rating and he said 'the amp rating is probably fine.'

But, I am not sure how to interpret the spec sheet. The spec sheet says they are rated at 25 A. Does that that 25 A rating mean that 150 A total could be pulled across all 6 blocks? Or does that mean the total when summing the current across all jumpered blocks can't exceed 25 A?

• 25A Per block.. – Trevor_G Mar 12 '17 at 4:13

It means that they are rated to have 25A through their internal bus bar, and also though any wire-to-block connection point.

Note that these terminal blocks only have two screw connections; they are made to connect one single wire to another single wire. They also make jumper strips that connect in through the top of the terminal blocks. These either screw into place or simply press in:

On page 46 of the full datasheet, it says:

Jumpers carry 100% of rated terminal block current.

So let's do a thought experiment. Say you have 6 LED panels that take 5A each. You jumper six terminal blocks together (one for each panel), and you connect your power supply to one of these blocks. In this case, you have your main power wire providing 30A to one of the blocks, which isn't allowed by the ratings.

Instead, you could make two groups of three blocks each. That way you wouldn't have any single connection points that are over the rated current.

By the way, instead of buying the jumper strips you could just use wire to daisy-chain multiple blocks together. This requires multiple wires to be installed under the same screw clamp, which is not allowed by many industrial electrical codes.

• I think your thought experiment is helpful - I saw the statement on jumpers in the datasheet, but I am not sure I understand it. So, let me continue your thought experiment and see if I learned anything. I could use a 50A rated block at the load and a 50A block at the ground, the jumpers then distribute the ~5A needed to each 25A block and not 30+A through each block. – TBP Mar 12 '17 at 13:51
• @TBP Yes, you got it, as long as the jumpers were made for the 50A blocks and not the 25A blocks :) But, I'm not sure that the 50A jumpers are compatible with the smaller, 25A blocks... Hmmm... – bitsmack Mar 13 '17 at 16:43
• Thanks for confirming that. Interestingly, they pretty much make one screw in jumper for the 1492 series it works, at least up through the 50A block. So I am good there. – TBP Mar 14 '17 at 19:01
• @TBP Sweet! That's good to know :) – bitsmack Mar 14 '17 at 19:15