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I obtained the following wire 22 Gauge Stranded Hookup Wire from Radio Shack:

Type/Style: AWM/1007
Wire Gauge: 22 AWG
Insulation Thickness: AVE. 0.42 mm
Rated Voltage: 300V
Temperature Rating: 80°C / 176°F

Use Limitation: Internal wiring of appliances; or where exposed to oil at a temperature not exceeding 60°C or 80°C, whichever is applicable.. Tags may indicate the following: 600V Peak - For Electronic Use Only.

I'd like to be able to hook up RAMPs 1.4 to my switching power supply with this wire. Will this work okay?

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22awg wiring is good for a max of 7A in this usage case. Your power supply can provide 30A. So it is definitely not large enough wire gauge for good wiring practice -- in the event of a short, you want the PSU's over-current protection to kick in before the wiring overheats. That would mean 14ga between the PSU and board. 16ga would probably cover your actual load requirements just fine, but we need to know a lot more about your printer to say that for sure.

12v systems need heavy duty wiring, at least on the main supply lines. You can use 22ga for individual power consumers, such as fans, extruder heaters, etc. (No heatbeds.)

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  • $\begingroup$ I think you mean "in the event of an overload". In the event of a dead short the protection should kick in almost immediately, well before the wires have any chance of heating up. $\endgroup$
    – Tom van der Zanden
    Mar 25 '16 at 18:30
  • $\begingroup$ It's not uncommon for PSUs to allow significantly higher draw than their rating before the overcurrent protection kicks in. For a high-current, low-voltage PSU like this, the supply wires, terminals, board traces, etc can provide enough short circuit resistance (a few tenths of ohms) that a dead short won't actually trip the overcurrent protection fast enough to avoid immolating undersized components. $\endgroup$
    – Ryan Carlyle
    Mar 25 '16 at 19:52
  • $\begingroup$ Yet another reason why we should all be switching to 24v PSUs... way safer than 12v PSUs. Less risk of wire heating, smaller wires for less wire fatigue on moving parts, and much more reliable tripping of over-current protection. $\endgroup$
    – Ryan Carlyle
    Mar 25 '16 at 20:08
  • $\begingroup$ @RyanCarlyle When you say 22ga above do you mean 22awg ? Is ga shorthand for awg? $\endgroup$
    – leeand00
    Apr 10 '16 at 6:54
  • $\begingroup$ @RyanCarlyle I ended up using AWG 10 wire type MTW OR THWN OR THHN (it's a pretty thick wire) for the wires between the switching power supply and RAMPS 1.4. It's good up to 600V, it's overkill but I think it'll do the trick. $\endgroup$
    – leeand00
    Apr 30 '16 at 12:02
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That should be fine for powering RAMPS, steppers and extruders but it is on the thin side. To err on the side of caution you should use somewhat ticker wires. However, you should definitely use thicker wires for the heated bed connection.

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  • $\begingroup$ Definitely not big enough gauge for a heated bed. Actually, it's probably not big enough for steppers and a 12v extruder either. $\endgroup$
    – Ryan Carlyle
    Mar 25 '16 at 18:15
  • $\begingroup$ @RyanCarlyle That seems to contradict your own statement that it's good for 7A. 7A is more than enough enough to power an extruder and steppers though if you have very beefy steppers and drivers to match you might run into trouble. $\endgroup$
    – Tom van der Zanden
    Mar 25 '16 at 18:26
  • $\begingroup$ A 40w 12v extruder draws 3.3A alone, that's half your "absolute max" wire capacity. Then each stepper is likely to be between 0.3A and 2A, depending on stepper specs, driver selection, current setting, etc. (PSU load is max 1.41x higher than the current setting at half step positions with both coils energized.) Call it 1A each, w/ four steppers = 4A. Now you're over the wire rating, before considering the controller board and fans. You MIGHT be ok if you preheat with motors de-energized, and have good motor selection so the chopping drivers run efficiently and reduce motor draw from the PSU. $\endgroup$
    – Ryan Carlyle
    Mar 25 '16 at 20:00
  • $\begingroup$ And don't forget, 7A is "chassis wiring" rating, which means the wire is allowed to heat up considerably. Conservative rating should be a fair bit less than that. $\endgroup$
    – Ryan Carlyle
    Mar 25 '16 at 20:02
  • $\begingroup$ The 40W extruder example is a bit contrived, since PWM will keep the average power draw much lower than the maximum (and during heat up, steppers would generally not be enabled). The video shows that 3A can be enough to run a printer just fine. I agree 22AWG is on the thin side, and edited my answer to reflect that. If you want to get completely technically within the specs, you have to account for the fact that the connectors on RAMPS aren't even rated for 30A so no matter how thick you make the wires, you'll always have that point of failure before the PSU enters protection mode. $\endgroup$
    – Tom van der Zanden
    Mar 25 '16 at 20:16

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