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I am currently building my own 3D printer, it is all set and ready to go but I seem to be having issues with the silicone heat bed I purchased. The motherboard I use is from the Flashforge Creator Pro for it allows me to use dual print heads.

The silicone heater bed I purchased has 3 leads with the capabilities to be run three phase which was something I did not ask for nor did I expect. Now I've noticed that when I plug it into my board, the board says that it is sending power to the bed but it doesn't seem to heat up. Also when I wire its thermistor, in it keeps reading around 110°C at initial startup and would not recognize room temperature.

One last thing, my power supply is a 24v rather than the standard 12v. I'm stuck because I have no idea how to resolve these issues. Do I need a different heat bed altogether or should I make it 3 phase and if I do how would I go about doing so? The pictures are too large so here are the links:

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  • $\begingroup$ A 3 phase bed sounds suspiciously like one meant for mains power. Are you sure this is a 24V bed? $\endgroup$ – Tom van der Zanden Feb 7 '18 at 8:18
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    $\begingroup$ This is what I purchased aliexpress.com/store/product/… $\endgroup$ – LDF Feb 7 '18 at 9:51
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    $\begingroup$ "110 v 220 v Silicone Rubber Heater": perhaps one pair of wires gives you the 110V version, whereas the other pair would give you the 220V version? In any case, hooking up a bed meant for 220V up to 24V will only give you around 1.2% of the designed output power, so it's not surprising that it doesn't heat up noticeably. Try measuring the resistance between the various pairs of input wires to figure out what voltage they're meant for. $\endgroup$ – Tom van der Zanden Feb 7 '18 at 10:30
  • $\begingroup$ Don't use this for a 3d printer. The seller has specified the wrong part for the job. $\endgroup$ – Sean Houlihane Feb 7 '18 at 15:44
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    $\begingroup$ Do any of the answers helped you to get an answer on your question or helped you come to your own conclusions then please do vote and accept an answer. This helps us reduce the unanswered questions list. Found an other answer (then the already posted) yourself? Please add that answer (and accept after 48 hours) to share your experience with the community. If you have not been able to address the problem please update your question. $\endgroup$ – 0scar Sep 7 '18 at 6:16
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What you purchased is probably a bed that can be configured for either 110V or for 220V, depending on how you hook up the wires: the bed contains two heating elements, hooking these up in parallel gives you the 110V version, hooking them up in series gives you the 220V one.

If you attempt to use this bed with a 24V supply it won't work. The power dissipated by a heater is proportional to the voltage squared. Depending on which way you hook up this bed, you'd either get 1.2% of the designed power (220V mode hooked up to 24V), 4.8% (110V mode hooked up to 24V) or 2.4% (one half of the 110V circuit hooked up to 24V).

If my assumptions are correct (which you could verify using a multimeter to measure the resistance between the various pairs of wires), then the only way to use this bed is to connect it to mains power and use a (solid-state) relay to control it. However, please get advice from somebody experienced in working with mains electronics before doing this. Do not attempt this on your own.

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    $\begingroup$ Excellent answer. If your printer has a moving bed, I'd further discourage you to use a heting mat running on mains. The cables feeding into the mat will be subject to continuous mechanical stresses and - in the mid-long run - will fail. This is true for any cable/voltage, and this is why there are so many mods to prevent heated bed cables for bending too much. However the danger posed by a a 240V AC cable failing is orders of magnitude more severe than that posed by a 24V DC one. $\endgroup$ – mac Feb 7 '18 at 15:06
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    $\begingroup$ @mac: not inherently, with a grounded chassis and properly-rated fuse. 1A @ 240v is less fire-prone than 10A @ 24v, fire will be the result of frayed wires from flex. Strain relief is a solved problem for moving cables, just cost-cutting printers don't tend to use it because not using zip-ties is cheaper than using them. That said, the FFCP only moves the bed in Z, so it's mostly moot :) $\endgroup$ – Bryan Boettcher Feb 7 '18 at 17:56
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    $\begingroup$ @LDF How large is the printer you're building? Is it a 600mm X 600mm build plate (the one you linked to)? In that case, it's not a good idea to try running it off that board. The power required is too large; you're going to overload the motherboard and set something on fire. Please be careful, it doesn't really seem like you know what you're doing. $\endgroup$ – Tom van der Zanden Feb 7 '18 at 20:13
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    $\begingroup$ The silicone heater you have now is probably your best option, but it requires mains power and a (solid-state) relay to control it. You can't run a heated bed this large off the heated bed output of your motherboard; it requires too much power/current. $\endgroup$ – Tom van der Zanden Feb 7 '18 at 20:43
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    $\begingroup$ if you use a mains powered heater, you should earth the bed with a cable that is able to carry the fault current for long enough to blow the fuse (i.e. some ~100A for a few seconds). $\endgroup$ – Sean Houlihane Feb 7 '18 at 23:09

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