LED Display With 4 Power Supplies: Calculating Total Amps, Wire Gauge, and Connector Rating

I am a DIY user trying to understand basic electrical knowledge. I’m not sure if I am in the right place to ask so if not, I’m sorry.

I have an LED display screen (see attached photos)that has 4 power supplies connected together (maybe the term is looped). We are running on 100-120 volts and according to the label each power supply draws 6.8 Amps.
I am assuming (and need clarification) that the total load is 27.2 Amps?

If the above is correct (27.2 Amps), does that mean the supply cable (that is connected to the first power supply - e.g main line input) needs to be something like a 30 Amp 10 gauge wire?

Does the wire gauge between each power supply need to be 30 Amp 10 gauge wire or can it reduce in size towards the end power supply?

Also, the blue plastic (PowerCon type) input connector that receives the main line input is only rated for 20 Amps.
Doesn’t it need to be 30 Amps???

Any assistance would be most appreciated.
Thanks

Hi

From the pictures it looks like you have 4 x Power Modules in parallel, fed by 2 x Input Connectors (splitting load between such).

In theory you are correct in that at ~110v each would draw 6.8A and your concerns for cable sizing etc would be correct. However that is the maximum power they would draw when outputting 5 Volts at 60Amps. You will most probably find that the modules are not approaching anywhere near that, as to do so much thought would be given to heat dissipation and the practicalities of cable sizing to name just two considerations.

I suspect that if you measured the input and output currents of each module you will find that the values are well within cable / connector capabilities. A current clamp would be the easiest method but not all do DC.

Hope this helps,
Regards

Thanks for your help.
The second blue connector is to link to another display and not an input.
I will try to test the amps being used with a DMM and see what reading I get.
Can you tell me where to connect the DMM to record the total load?
Thanks

Hi

Daisy-chaining units via the two blue connectors makes sense (in/out) and reinforces my view that the modules are not being driven hard at all.

A current clamp (if available) would be my choice but if you only have a DMM then the first thing is to check your DMM capabilities. What is the maximum amperage it can safely handle? Handheld DMM's usually have a 10A maximum and may not do AC at all, only DC, or AC at a far lower amperage. Double check capabilities before anything. We will assume though that your DMM can indeed handle 10A AC and that you have appropriate test leads with no signs of damage.

As the 110v AC input is feeding multiple modules, each potentially drawing around 6A (doubt if they are) the combined load could easily exceed 10A.

If you are confident working with mains voltages, and I cannot over stress the need for safety awareness, I would measure the current going into each module in turn, then to find the total current drawn, add the values together. If you are not confident with Mains, get a current clamp.

Disconnect the unit from the mains completely (switched off with nothing connected to blue connectors). At the Live input on each of the modules (L) you can see from your photos that you have two brown wires. To test a module you will need to remove both brown wires from the module and safely and securely connect them together, perhaps with a suitable piece of connector strip / terminal block. Then, making sure your DMM is set to highest Amp range and the correct terminals are used (most use Common and a dedicated 10A terminal) you will need to connect from the Connector Strip / Terminal block to the module under test (L). I don't know what probes you have but they may allow you to screw them in place or you may need to use wire to extend connections. However if you are doing this I again cannot over stress the need for safety. You must ensure that there is no chance of you coming into contact with the Mains voltages and no chance of them coming into contact with anything else. "It's OK, it's just a quick test" is a quick route to the cemetery.....

Double check connections are safe and double check DMM settings and terminals. Position the DMM so that you can clearly read the display without touching it. Connect the Mains at the blue connector. Keeping your hands and everything else clear, switch on the Mains to the unit. All going well your DMM will display the current drawn by the individual module you are testing. Make a note of the value. Switch off the Mains. Disconnect blue connector. Double check you are disconnected from Mains. Remove DMM and reconnect brown wires to the module under test (L).

If you repeated the above for each module and added each value together, you would have the total current drawn by the unit. However even a modest clamp would be far easier and safer. If you have no reason to suspect anything is wrong, you could assume all modules are driving roughly equally (no guarantee though) and just multiply your first reading by four to get a rough guesstimate of total current.

Hope this helps.