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I have a Bambu Carbon X1 3D Printer in my shop. My shop was built before grounding was required; so it has a GFCI Breaker installed to protect new 3-prong electrical outlets with their applicable "No Equipment Ground" stickers.

The 3D Printer has a fairly large power supply, and generates significant amounts of "leakage current" (AC to Ground). The documentation states that the leakage current is about comparable to running a washing machine, but states that it "complies with GB4341 and IEC62368 safety standards." Touching the metal frame of the printer sometimes has given me a noticeable continuous zap.

I'm concerned about the safety of this setup. In theory, the GFCI + Compliance with standards for leakage current would make this safe, or at least a low risk. Or would it?

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    I'm curious as to why you don't add a few ground rods and correct this problem. A noticeable zap is not good and should be corrected. Is your main panel grounded?
    – JACK
    Sep 20, 2023 at 16:27
  • @JACK The main panel is grounded. It would have had even it's own ground rod, except that a ground rod is (as far as I understand) not recommended for sub panels and should instead be provided by house ground (as the shop is a sub panel from the house).
    – G.S.
    Sep 20, 2023 at 16:50
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    Panels don't require ground electrode systems (rods, plate, ufer, etc); buildings do. Can have all the sub panels you want in a single-building house and only one GES is required (connected to the main panel). If a sub panel is in a building detached from the main building then that building needs its own GES, connected to the first subpanel in that building.
    – Greg Hill
    Sep 20, 2023 at 16:55
  • I should clarify @GregHill just to make sure we are on the same page. Our house has a panel, grounded, with grounding rod. Our sub panel runs from the main house, has separate neutrals and grounds, and the neutrals and grounds go back to the main panel. We have a ground rod installed in the shop in addition to the house, but I can't remember if it is attached to the ground bus bar in the sub panel or not (the shop, and the rod, were originally a fusebox) and would need to take off the cover to check - but either way it runs to house ground.
    – G.S.
    Sep 20, 2023 at 16:59
  • That's good; under NEC detached buildings should have both a local ground electrode system and a grounding conductor running back to the main panel.
    – Greg Hill
    Sep 20, 2023 at 17:09

2 Answers 2

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A GFCI should detect and interrupt leakage current no matter what the destination of the leakage -- the leakage doesn't have to go into an equipment ground conductor. If you walk up and touch that printer and get a zap, current is going somewhere. If it exceeds the GFCI's limit then yes, adding a GFCI would stop the zap by interrupting the circuit. I guess that's "safer" because it limits the magnitude of the potential shock, but it's still not right. It could be annoying in a practical sense too: the GFCI may protect you from shock and ruin your print in the process by cutting power to the printer.

We can't really say whether the power supply is leaking excessive current or not. Either way, connection of the metal chassis to the equipment grounding system should get rid of the personnel shock potential by draining any leakage away into the grounding system.

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https://blog.bambulab.com/quality-assurance-and-operations-update/

The printer's safety in all operating settings meets the national standard GB4341 and the European IEC62368 standard. To achieve fast printing and heating, the printer's heating power is relatively large, and so is the leakage current. X1 and P1P have a similar leakage current as a typical washing machine. This is especially noticeable when many printers use an AC power supply of greater than 200V to print high-temperature filaments. Please choose a circuit breaker with sufficient leakage current to avoid this problem.

https://bambulab.com/en/about-us

Right now we have three sites located at Shenzhen and Shanghai in China and Austin, Texas of U.S.

https://www.reddit.com/r/3Dprinting/comments/10rhg2u/bambu_labs_is_sus_china_exploiting_you/

so assuming a washing machine means ~ 10 amps at 120V, let's say 1000 watts of leakage power. What a decoy saying complies with GB4341 and IEC62368 safety standards. I would have to look them up specifically, would not surprise me those standards technically have nothing to do with electrical safety and the leakage current is out of their scope.

national standard GB4341 I initially said I couldn't find it, I think i found it https://codeofchina.com/standard/GBT4341.1-2014.html English Name: Metallic materials-Shore hardness test-Part 1:Test method

Let's have an academic exercise for a sec - you have a GFCI protection, which should trip at 5 milliamps leakage current between load to neutral; the ground on a GFCI serves no purpose in the ground fault circuit measurement. It's greater than ~ 5 mA difference measured between current going out and coming back on two wires in a single phase application...

you said so it has a GFCI Breaker installed and also said Touching the metal frame of the printer sometimes has given me a noticeable continuous zap.

Did you get your GFCI breaker with the printer?

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  • The GFCI breaker is a Square-D Homeline model with Plug-On Neutral, with a built-in CAFCI.
    – G.S.
    Sep 20, 2023 at 21:30
  • Also, the "GB" in GB4341 is actually this: en.wikipedia.org/wiki/…
    – G.S.
    Sep 20, 2023 at 21:31
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    10 A of leakage current is completely absurd and certainly not what they meant. They wanted to say that the leakage of the printer is similar to the leakage current of a washing machine.
    – TooTea
    Sep 20, 2023 at 21:49
  • IEC62368 is the current safety standard for "general purpose" power supplies (wallwarts etc) and has been adopted by UL as UL62368... Sep 21, 2023 at 2:36
  • @ G.S. your link to wikipedia for GB4341, um there's no 4341 on that page when I do control-F.
    – ron
    Sep 21, 2023 at 13:50

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