It Begins .. Wiring to a 12V-25A PSU with a 220V Heated Bed

  • Hi,
    Received my board today, excellent time to delivery by the way..

    I am upgrading an "older" P3 Steel XL with a 220V Heated bed. It has one 12V-25A PSU and was running a simple 5V relay to the heated bed and the 220V power source.

    First question, my old Ramps had four (2+, 2-) 12V wires from PSU to power input and I read that I could connect both to the one power in on the Duet WiFi.
    Question is: do I need to connect both sets (4 wires) or is one set (2 Wires) enough when I will be powering the Heated bed from 220V via an SSR anyway?

    Second question, I have a few 25A and 40A SSRs around so plan on using one of them to connect the AC Side to the bed & 220V and then run the Duet Heated Bed connections to the DC side of the SSR? The SSR accepts 3-32VDC..

    ANy input would be welcome ..

  • One set of wires running the Duet will be fine. Connect the +/- of the Duet's bed heater output to the SSR +/- on the DC side.

  • administrators

    +1 for the previous response.

  • yup you only want 2 wires for 12 volts.(12+vdc and return). PC power supplies often have multiple rails so you can share the load across different supply lines not that it matters since you only need one 12v source correct? Some rails have more amps than others BTW so not all 12v lines are the same. Check manufactures site for details if PS is not clearly labeled. i run ssr and 110 v 750 watt 300 x 300 mm bed heats up to 65c in about a minute so just maybe overkill depending on bed size. LOL recommend in line fuse to limit amps based on what you need and not what is available. you probably should not need anywhere near 40 or even 25 amps to run it. With that kind of potential, highly recommend massive chassis ground especially for the bed. Can't remember if it is 5vdc or 3.3vdc but if pc power supply, you can add that to the duet wifi too. hope this helps… 🙂

  • Thanks for all the answers.. Have begun wiring up ..
    Best Regards

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