Code Compliant (NEMA?) Power Supply Wiring/Enclosure Advice?

[gchristopher]

For those of us using non-PC power supplies (Meanwell RSP-750-24 in my case), can anyone recommend a power supply enclosure system that will be electrical-code compliant?

The basic problem using this power supply inside the printer is that now there are 120AC, 12VDC and 24VDC wires all sharing the same space inside an ungrounded wooden box that is also an electric heater with moving parts. I'd like to move from this DIY setup to something that would be up to code for use in a residential space, especially to reduce the worry if I ever leave a print running unattended.

My understanding is that the basic idea for electrical compliance is to put the AC and DC wiring into separate chambers of a grounded, fire-resistant box.

Does anyone have some recommendations of where to start and what direction to go? Any particularly good references for how to make it safe enough to actually be up to some kind of residential wiring code? It seems like home LED lighting deals with this a lot, but their power supplies tend to be physically smaller, so I haven't found a junction/project box that's sized for the Meanwell yet.

I was thinking that the most straightforward and future-proof solution might be something like building a really beefy external supply box:
- Find an off-the shelf grounded metal project box that fits the power supply, though perfect separation of AC and DC wiring will be impossible since the screw terminals are not that far away from each other on the supply. This will be physically separate from the printer.
- Fit the project box with a standard fused power jack with a switch. (Lots of people seem to be using a one that takes a standard micky-mouse AC plug, like this one, only installing it directly to the printer.)
- Run 24V out of the project box, to an appropriate DC jack installed in the printer. (Are there better places than Mouser/Digikey to look for those kinds of cables and connectors?)
- Keep the rest of the DC wiring, 12V step down, motor, hot end, heat bed, in the printer, because it's significantly lower-risk than having AC household current wiring in there.

Any comments and suggestions would be appreciated! I haven't seen a lot of discussion on this topic, but it seems like the kind of safety issue that would be really worth finding the best and most cost-effective answers. Thanks!

[rurwin]

This might be a good starting point: https://en.wikipedia.org/wiki/Appliance_classes

I think IEC6044-1:2007 is the current applicable standard. It is only available for money, and rather a lot of it. However, the Indian standard seems to be identical (albeit the 2002 edition) and does seem to be available: https://law.resource.org/pub/in/bis/S05 ... 1.2003.pdf
Warning: it's long, complex and you probably don't need most of it.

[Eric]

Ungrounded is a scary word primarily when you're talking about highly conductive enclosures that can shock you. Wood is a very poor conductor. Besides, your power supply is already a grounded metal box, assuming you've correctly attached the AC ground to it and the 3-prong outlets in your house are properly wired. Personally, I think external power bricks are more dangerous than internal supplies, after seeing what the unaware will do with one (e.g. in-use power brick completely buried with discarded clothing in kids room).

For residential use, you have other safety issues to consider for unattended operation. First and foremost is the risk of fire. You want the printer in a location/situation that won't burn down the house if fire happens. Enclosing the whole thing in a metal box is one option. Automatic extinguishers and emergency electrical shutoffs are other things to think about.

Another consideration is isolation from family spaces. You don't want your family to be continuously breathing the microparticles that 3d printers put out. If you can't isolate, then you need to think about ventilation solutions.

[Xenocrates]

If what you're looking for is just separating the AC from the DC lines, then I suggest a Nema 1 enclosure such as https://www.automationdirect.com/adc/Sh ... /SC101204G

Put a knock-out with strain relief in for the AC and the DC, switch in another knockout or a drilled hole, and use a 4 conductor solution to connect the remote switch of the power supply to the printer. For the DC power connectors, I recommend Power Poles (Use the crimper Powerwerx sells, don't use pliers), likely using 45A contacts and 8 gauge silicone wire. This gives you a keyed connection on the printer, with the ability to switch things on and off, that can handle the amperage of the entire power supply, that still gives the printer the ability to be turned off by the switch or turn itself off. Put a fuse block and a nice beefy 15-20A switch (Power supplies have large inrush currents and inductive loads due to the transformers internal to them). I might also put a fuse on the DC side, especially if you use a wire less than 8 AWG. Size the fuse for the lowest amperage rating carrying the full supply (AKA, until it gets to a power distribution block inside the printer). I would also fuse each output from the power distribution block to protect downstream wiring. I also recommend that you sleeve/sheath the cabling from the power supply to the printer, either in flexible steel conduit or a few layers of big heatshrink, to prevent damage to the insulation or the cabling from being completely sheared through. There is a lot of amperage there, and it can mess things up even though the voltage is low.

[gchristopher]

Thanks for the replies! Hopefully I can come up with something cheap-ish in the direction of a power enclosure.

Yes, the hope is to bring the operation of the printer up to a level of safety and reliability to leave running unattended in a residence. The issues you all raise all definitely have to be addressed.

Any other ideas or comments?

[Eric]

If you have pets, assume murphys law is in full force.

Once, I had a cat somehow get my binoculars strap looped around his neck, which of course caused the binoculars to chase him when he pulled away. He ran around madly, then jumped on the kitchen center island to get away....but the binoculars kept chasing him, knocking off dishes and glasses. He ran up the stairs and he finally got away from the evil binoculars when the metal strap connector bent open. It was actually quite amusing, except for the mess in the kitchen that had to be cleaned up. A few glasses died that day, but amazingly the binoculars survived being slung around like a flail.

The point is, if that panicked dash had sideswiped a printer, the printer probably would have ended up on the floor. There's an amazing amount of potential force in a 15-pound cat.

[barry99705]

If you have pets, assume murphys law is in full force.

Once, I had a cat somehow get my binoculars strap looped around his neck, which of course caused the binoculars to chase him when he pulled away. He ran around madly, then jumped on the kitchen center island to get away....but the binoculars kept chasing him, knocking off dishes and glasses. He ran up the stairs and he finally got away from the evil binoculars when the metal strap connector bent open. It was actually quite amusing, except for the mess in the kitchen that had to be cleaned up. A few glasses died that day, but amazingly the binoculars survived being slung around like a flail.

The point is, if that panicked dash had sideswiped a printer, the printer probably would have ended up on the floor. There's an amazing amount of potential force in a 15-pound cat.

About 91 jules.

[geneb]

x3 power bonus for "mad panic".

g.

[gchristopher]

Yeah, it seems safe to assume that dogs, cats, and small children are guaranteed to find a way to take down any printer they can reach.

[Swity1981]

It's like they have a sixth sense for electronics. One moment you have a perfectly functioning printer, and the next, it's a victim of curious paws or tiny hands.

[Swity1981]

It seems like there's an unspoken pact among dogs, cat , and children to view printers as personal enemies. They have an uncanny ability to find and exploit weaknesses in even the most robust models.