Help with Current(mA) draw!

[AlexTheGreatester]

I need some help understanding some electrical stuff! I have a few large format 3d printers that come with 6amp power supplies. The company I bought them from states that each printer needs 6 amps to properly run the UV array. Now here is where confusion comes in. I use an electrical monitoring plug. One of those ones that gives you the Power(W), Voltage(V), and Current(mA). They say that the printers are only drawing 1130mA when running with the UV array on and 540mA on the off layers. If that's right they are only drawing around 1.1amps, right? That's no where near how much they should be drawing according to the company. Am I misunderstanding something or are they not getting enough power.

 

[AlexTheGreatester]

I need some help understanding some electrical stuff! I have a few large format 3d printers that come with 6amp power supplies. The company I bought them from states that each printer needs 6 amps to properly run the UV array. Now here is where confusion comes in. I use an electrical monitoring plug. One of those ones that gives you the Power(W), Voltage(V), and Current(mA). They say that the printers are only drawing 1130mA when running with the UV array on and 540mA on the off layers. If that's right they are only drawing around 1.1amps, right? That's no where near how much they should be drawing according to the company. Am I misunderstanding something or are they not getting enough power.

In case it matters, the power supplies say on them:

Input: 100-240V~ , 50-60Hz, 2.2A
Output: 24V, 6.66A, 160W

And the reason I'm asking the question is because the company is telling me that I probably don't have enough power running to them and I should run a new circuit from my breaker for each printer so they each have their own 15amp circuit.

 

[Lucien Nunes]

The maximum output current rating of the power supply unit is 6.66A at 24V. Multiply the two to get 160 watts maximum power rating. Your power meter is measuiring the input current as 1.1A at 120V. Because the voltage is five times higher, the current will be about five times lower for the same wattage, i.e. it works like a transformer. 1.1 x 120 = 132 watts going in. So if the power supply is say 90% efficient, it is outputting about 120 watts to the printer, or 5A at 24V. They would be reasonable in saying it needs 6A to give a safety margin. All sounds fine to me.

If there were a problem with inadequate electrical supply, the units would probably just keep shutting down and restarting, or a breaker would trip. No idea why they think that.

 

[AlexTheGreatester]

The maximum output current rating of the power supply unit is 6.66A at 24V. Multiply the two to get 160 watts maximum power rating. Your power meter is measuiring the input current as 1.1A at 120V. Because the voltage is five times higher, the current will be about five times lower for the same wattage, i.e. it works like a transformer. 1.1 x 120 = 132 watts going in. So if the power supply is say 90% efficient, it is outputting about 120 watts to the printer, or 5A at 24V. They would be reasonable in saying it needs 6A to give a safety margin. All sounds fine to me.

If there were a problem with inadequate electrical supply, the units would probably just keep shutting down and restarting, or a breaker would trip. No idea why they think that.

That all makes sense. This is what I was told by them.

"Each machine will draw about 4-5 amps on full load. 4 machines will put you between 16 and 20 amps. Most residential circuits are 15 amp. That would put you past the 80% load recommendation by CSA and will cause electrical issues if it doesn’t start blowing breakers."

Which is nowhere near correct from what I gather. As the machines only draw around 2A from my residential circuit.

 

[Lucien Nunes]

Perhaps whoever wrote that isn't familiar with the machine and just read it from the spec, not realising it was 4-5A at 24V not 120V AC. Anyway, four 160W power supplies will be fine on a 15A circuit, provided it isn't powering a bunch of other stuff as well. If it's GFCI-protected you can sometimes max out the permissible ground leakage current with units like this and get random GFCI trips, before you reach the maximum load current. But again with four power supplies it should be OK for leakage too.