0

Most outlets in my house are non-grounded (line and neutral contacts only). I just bought a Hakko fx-888d soldering station, and immediately noticed that touching the iron-station cable gives the same sensation as when I plug in my aluminium Macbook. This sensation disappears when I unplug both devices. I measured the voltage between the ground (from a grounded outlet in the bathroom) and the Hakko cable; it was about 100...110 V (I used the AC regime of the multimeter).

What causes this voltage? Is it dangerous for me or for electronics?

UPDATE: I live in the Netherlands, where having 2 contact outlet is allowed. The human safety is ensured by RCD = GFCI. The house is not that old and is well wired (with copper) and grounded, where required. While I'd be happy to improve it and rewire the ungrounded outlets, it doesn't make much sense as I am renting.

Also, plug orientation here is arbitrary (plug can be inserted in the outlet in two ways), so the design never relies on which wire is neutral and which one is line.

texnic
  • 207
  • 1
  • 10
  • A duplicate of https://electronics.stackexchange.com/q/267146/117785 and many other questions about AC-DC converters leakage. – Ale..chenski Mar 16 '19 at 20:18
  • @Ale..chenski Different device, but same issue. Likely a conventional step-down transformer with poor primary-secondary isolation. Capacitive coupling can be substantial. –  Mar 16 '19 at 21:02
  • If your house is old enough to be an ungrounded system, it is possible many of your plugs are wired incorrectly with hot and neutral reversed. For parts like casings that should be attached to ground and nothing else for safety reasons, when they are left floating, they can sometimes be brought to substantial voltages by parasitics. It would be wise to get a plug tester and test all of your plugs, and of course it is unwise to use a device that requires a ground with an ungrounded source. – K H Mar 16 '19 at 23:59
  • This sensation you're describing, can you describe it better? You mention it as if it is normal, but generally speaking, you *should* feel nothing whatsoever when you plug in a device, Macbook or otherwise. Is the sensation you describe the sensation of getting a 120V shock? If so, cease the activity *immediately* and troubleshoot your system or if you don't have the necessary skill, hire an electrician. Even if they don't kill you (50-100mA at 120VAC is about right to stop the heart), 120V shocks can cause permanent heart problems and should be avoided. – K H Mar 17 '19 at 00:03
  • Can you also provide a picture of the part of the cable you are referring to? My Hakko uses an insulated cable with the only exposed metal parts being the tip and tip holder. Where is the exposed metal you are measuring voltage to ground from? – K H Mar 17 '19 at 00:08
  • @K-H, FX-888D is an ESD station, so it has conductive plastic parts. I am measuring by touching the cable insulation with the probe. Also, I am in Europe, neutral and line can be swapped here. And no, I am not getting shock. The question about the printer the guys linked provides more detail. But thanks for your care anyway! – texnic Mar 17 '19 at 00:13
  • @Sparky256, the word "poor" doesn't match Macbook Pro in my mind :) Is it really a bad design/implementation or something physically inavoidable? I even wonder why they ground unibody in the first place. – texnic Mar 17 '19 at 00:19
  • Hmm good to know that's a property of my iron(It's esd safe as well). In that case it seems likely that your casing is internally connected to "neutral" on the plug and the plug is miswired. Sadly common mistake, especially on old systems. Power down circuit at panel, meter plug, pull the plug and check that neutral is connected to wide prong. If it is, reenergise and meter neutral voltage to ground. If the neutral is live, follow it back to the panel box by box, fixing any problems on the way. Then check all downstream boxes that split off the line you just checked. – K H Mar 17 '19 at 00:23
  • At any rate don't use equipment that requires a ground on an ungrounded system. Add a surface ground if necessary(ugly, but does the trick), and if your house is ungrounded or wired in aluminum wire, every time you do any work on it, you should be looking for the appropriate time to gut it and replace the wiring, or if you have a lot of money or the finish is expensive, hire an electrician to do an upgrade with minimal damage(homeowners can't pull concealed work permits in most areas). If you do have H/N reversal problems, the wiring of your entire house is suspect and should be checked. – K H Mar 17 '19 at 00:26
  • Also, if you like apple products, that's fine, but be aware that they are not built to a significantly higher quality standard in many ways than their cheaper counterparts. You should not operate with the illusion that their engineering is superior in such a way as to make any specific intrinsic flaw unlikely. As far as why exterior metal parts would be grounded, the purpose of grounding is to provide a low impedance path to earth for fault currents. This ensures that when they flow, fault currents will be large enough to trigger their associated safety apparatus. – K H Mar 17 '19 at 00:36
  • If you'd like a better idea of what you're getting with an apple product, go on youtube and watch a number of Louis Rossman's repair videos and listen to his rants. Generally speaking you get something very nice, that is indeed fairly well(certainly not flawlessly) designed, but above average, typically with high end technology, and you pay a large markup(1.5x-2x) for the look and the name as they are status symbols. When, not if, something goes wrong, you can expect a high probability of having to replace the device, even if it is repairable. – K H Mar 17 '19 at 00:42
  • Not only is it potentially unsafe, using that soldering station in an ungrounded outlet has the potential to damage sensitive electronic components such as ICs, LEDs and MOSFETs. – Jasen Слава Україні Mar 17 '19 at 05:46
  • @Jasen, perhaps you could convert it to an answer and elaborate a bit further? If I understand the linked answer correctly, this effect is well known and safe. But I am still confused by physics as in where does the connection between ground and the source of this voltage come from. – texnic Mar 17 '19 at 08:05
  • @Ale-chenski, I read your other answer a few times and still cannot understand the source of my voltage properly. Care to add an answer here with a simple diagram? I don't see how a transformer (connected to line and neutral) would put voltage on the ground and why voltage would be less than half of mains. – texnic Mar 17 '19 at 08:25
  • Since it appears that the 888D station uses an AC transformer as the primary section of AC-to-iron conversion, this topic has a likely answer to your observation. https://electronics.stackexchange.com/a/410912/117785 – Ale..chenski Mar 19 '19 at 03:09
  • Also, since your country electrical system doesn't have earth ground, you need to make your own grounding wire, check this internal image of 888D, https://2.bp.blogspot.com/-W8i_VMeDOOk/UTdkQM9FURI/AAAAAAAAChk/n4beO-DOeqk/s640/IMGA0283.jpg it has a screw terminal with grounding symbol. – Ale..chenski Mar 19 '19 at 03:12

1 Answers1

0

Plug config. doesn't really matter in case of AC supply as long as you don't have dual supply systems (in some countries you can get both DC and AC supply on request to your house) .

Having an Earth connection is a good safety measure since the electrical wiring wears over time due to the heat produced in conductor inside and the aging insulation around the wires ,which will start to conduct electricity slowly over time .There is chance that at some point of time the insulation of whole electrical circuitry in your house could fail and can cause electric shock of max. supply voltage while using home appliances due to leaking current .

And also Earthing provides safety for the circuit itself avoiding/delaying possible fire accident due to shorting between the Live and Neutral wores incase of failure of wiring insulation .

Summing it all up ,I'd suggest you to change all your sockets in the house to 3 pin sockets (with dedicated Earth supply I mean) and provide proper earthing and use appliances with earth connection as much as possible .

Aron
  • 1
  • 1