Rumba plus : Custom Hotbed Build - Power Supply Question

Hi,
I'm looking for some help with powering the hotbed and Rumba Plus motherboard. My build is a custom build because I wanted a bigger print area for more capabilities so I have four(4) beds connected in a square shape, well I figured I could connect it parallel to the board. I have done the math for this and I hope it's right. I wanted to know if the ATX power supply I chose is the right decision and what would be the best route to take. How would you do it? I'm new to all this but the thought, "Go big or go home", crossed my mind so here I am lol.
For some reason it wont let me attach pictures from my phone, so if I find a way to do so I'll upload pictures.
The ATX power supply is a EVGA power supply-80 plus 500w
+5V - 20A
+3.3V - 24A
+12V - 40A
-12V - 0.3A
+5VSB - 3A

The hot beds are also in parallel to each other.
1 hotbed =
12V
10A
120W

Your PSU is inadequate. The bed heaters will max out the 40A rating of the PSU, leaving nothing for the extruder heater, stepper motors and fans. Also it's hard to manage 40A of current.

A much better option for heating large print beds is to use a silicone heater, either AC mains voltage if you take the appropriate safety precautions, or 24V if you want to use low voltage. Choose the silicone heater power rating to provide about 0.4W power per square cm of bed, and choose a size slightly smaller than the bed plate to leave a margin around the edge for fixings.

If you want to persist with using PCB bed heaters, then if they are dual voltage you can wire them for 24V and connect them all in parallel. Choose a 24V PSU rated 600W or more.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ok, thank you. Is that power supply for just the hotbeds or the whole system? Because I already have a 12v 20A power supply that I ordered before I realized it wouldn't work, so I could, in all reality, run separate power supplys for the hotbed and motherboard, which I have a set of 3D Printer Heat Bed Power Modules General Add-on Hot Bed Power Expansion Board MOS Tube High Current Load Module

Edited 1 time(s). Last edit at 01/04/2019 11:38AM by bricelee.

PCB bed heaters vary a lot in resistance and hence current draw and power. My suggestion of a 600W PSU was for running everything, but that assumes that your bed heaters really do draw 480W total, not more.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The specs on those beds state a 120 wattage draw each, but I done the math and the board only draws 12V how would that work with a 24V power supply? In parallel, voltage drops are the same as source. I mean its rated 12V to 35V, so i know it can handle it, i just dont understand the math.

Are the PCB bed heaters dual voltage (12V or 24V), or not?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes they are, I'm currently wiring them up for the 24V