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I have seen many people saying on this site and many other 3D printing websites that 24 V systems are safer, compared to 12 V systems. By safer, I am talking in terms of fires or other electrical and component failures.

Why would a 24 V system cause less danger? I would think that 12 V would be safer because it is very common (automotive) and many parts have been around for a while that use it. Although there are an increasingly amount of boards that support 24 V, many don't or need fuses or other parts that do support 24 V.

Also, many parts that I have used are rated for 12 - 24 V. A 12 V power supply can go a bit over fairly comfortably. A 24 V power supply can't without partially going over the rating.

If I had to build a printer designed with safety as a main priority, what voltage would be best?

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  • $\begingroup$ safer than what? further, are you confusing component safety and personal safety? $\endgroup$
    – Carl Witthoft
    Commented Jan 30, 2017 at 15:39
  • $\begingroup$ Safer than 12 V. I am talking about risks of fire or other electrical failures. Edited to include details. $\endgroup$
    – lights0123
    Commented Jan 30, 2017 at 15:41
  • $\begingroup$ A component rated for 24 V nominal will have enough margin to allow for supply variation. The more sensitive components are protected by regulators (which are likely to be specified to work up to 32 or 36 volts). Automotive 24 systems run at 28 V when on-charge, just as an example. $\endgroup$
    – Sean Houlihane
    Commented Feb 1, 2017 at 13:11

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The most important "safety" advantage when using 24V (compared to 12V) is that to get the same power, you only need half the current. A 192W heated bed would need 16A at 12V, but only 8A at 24V.

Since one of the most common safety issues is underrated screw terminals being used for the heated bed (just search for "3d printer fire"; you'll find quite a few pictures of charred plastic around screw terminals). For example, the screw terminals on RAMPs board are only rated for up to 12A. That would be okay at 24V, but well over the limit at 12V.

Since the wire gauge is dependent on current, you can also use somewhat thinner wires with a 24V system (or equivalently: wires that would melt in a 12V setup won't in a 24V setup). The power dissipated in a wire scales quadratically with current, so the same wire being used in a 24V setup would only waste a quarter of the heat of that wire in a 12V setup. There is also less strain on switching devices (such as MOSFETs or relays). The same applies here: power loss is quadratic with current.

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  • $\begingroup$ As a caveat, note to select correct hardware! E.g. a heated bed for 12 V with a fixed resistance will consume twice the current at 24 V, requiring thicker wires; hence just switching to 24 V is not necessarily more safe! $\endgroup$
    – 0scar ♦
    Commented Jul 26, 2019 at 8:16
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From a pure safety standpoint there is nothing about a 24v system that is distrinctly more safe than a 12v system. I see you added comments about something involving wire sizes. This is not really a factor.. I would say not knowing what wire size to use is a whole other issue. There is nothing stopping you from putting on larger wires.

The following websites verify the fact that a 24v needs smaller wires. Though again the system it self is not safer because the wires required are smaller.

I will also note the size difference is negligible anyways. It is not a major difference.

Now one exception to this. If you had a 24v and a 12v compatible board. I would pick a 24v. The reason is not that the wire sizes needed are different. But for the reduced danger of the CONNECTOR that the wires attach to. I see quite often in the flashforge owner group boards that have caught fire due to a cheap connector that can not handle the load for the printer.

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  • $\begingroup$ I have seen comments on this site with people who have seemed pretty convinced that 24 V is much safer. They have talked about how smaller wire sizes are needed, and how if you undersize wires it isn't as much as a problem with 24 V. I wrote this question to see if there were any other reasons that 24 V was preferred from a safety standpoint. $\endgroup$
    – lights0123
    Commented Jan 30, 2017 at 16:02
  • $\begingroup$ You want to use a higher load with smaller wires.. I think these guys are trying to get you to burn your house down.. Don't believe every yahoo on the internet... $\endgroup$
    – MakerModder
    Commented Jan 30, 2017 at 16:11
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    $\begingroup$ Their main argument is that with a higher voltage, a smaller current is needed, and therefore smaller wires. Undersizing wires will lead to heating, and not fires. Is that not true? $\endgroup$
    – lights0123
    Commented Jan 30, 2017 at 16:15
  • $\begingroup$ Wire size is a bit out of the scope of 12 v 24.. Someone with an EE background will come along and answer better than me. I have found some google results. However the size changes are marginal. $\endgroup$
    – MakerModder
    Commented Jan 30, 2017 at 16:25
  • $\begingroup$ For sure, updated with the info in question. Not a myth, more of an exaggeration. Again your printer will heat up way faster on 24v. $\endgroup$
    – MakerModder
    Commented Jan 30, 2017 at 16:34

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