Problem with power in bathroom. Dafuq just happened?

No idea what just happened, please if you have any ideas… Help?

Issue: no power on one outlet and bathroom integrated fan and controller not working

What happened? Wanted to put a small dehumidifier into my bathroom. It was working fine in another room. I turned it off, unplugged it, and plugged it in in the bathroom. There was a bang and electric smell from the dehumidifier. The fan and fan control stopped working, and there is no voltage on the power outlet when I measured with a voltmeter. Light and other outlets are still ok.

What did I check yet?

In the home fuse box there is no apparent fuse tripped. I didn’t find any other fuses or similar items in the bathroom or house. The fan control box also doesn’t contain any fuses, actually it doesn’t have any AC cables, only low voltage control cables. Maybe I’ll have to check the ceiling fan box…

The power outlet was the one near the toilet, where some silly ass warming Japanese style toilet seat is installed. I assumed maybe it’s silly unnarked 220V then, but in another bathroom the same outlet is 110V. Also on the switch box there seems to be only 110v…


The plot thickens: inside the fan box is a label saying “220V”.

Act 2: So I measure all voltages in the fuse box, all are 110V.

Act 3: Except for 2 fuses connected together, which are 0V.


Act 4: these fuses look not tripped to me, but then it turns out I’m not familiar with this kind of fuse. The “handle” is on the same position as all other fuses in the box, but there is a small window which shows a red color.


Act 5: fiddling with the fuse primes it again. Fan and power outlet work. Of course, this one power outlet in the home indeed is 220V, but no markings.


Lessons learned:

  1. Trust your instincts.


  1. If it smells like 220V, likely the issue was 220V.


  1. Don’t use German logic:
  • There need to be no markings on outlets that can damage appliances
  • just because two outlets in two bathrooms have the same function, it doesn’t mean they carry the same voltage


  1. I was looking for a 220V outlet for a coffee machine. Now I know I could place it in the shower. What could possibly go wrong :rofl:

Do we have a post of the month? That’s awesome. Glad you weren’t hurt.

1 Like

Worth it just for the memes.

Trust no one. Trust nothing.

1 Like

Now, now. The Germans are responsible for a great many top-tier appliances and electronics. Don’t be bitter just because your people didn’t manage to come up with this particular life-changing device.

1 Like

I’m wondering about the geographical distribution. I’m under the impression there are significant cultural differences between the Rhineland and Prussia, going back centuries. What part of Germany do most of the great German inventions come from?

A nice hot cup of coffee in the shower actually sounds pretty nice!

1 Like

Sneaky Taiwanese ‘electricians’ wire a 220V outlet as a 110V and don’t tell you until you plug in a 110V and it says boom! Does it make sense?


Yeah, as the smell already indicated, it’s more than just a fuse blown. Let’s see if Tatung provides spare parts. If not, I know the ODM of this dehumidifier now, they’re on Alibaba and might provide spares :+1:


Since I didn’t find Tatung spares easily, I decided to do what every engineer would do: check with someone who knows such stuff. Luckily there is a power supply developer sitting next to me, who pointed out that the damage might be contained to the AC part only (If one is lucky, and if the power supply design was good).

Turns out he was right. After googling a lot, I now understand a bit better what happened. I’ll share hoping it helps some other silly furinners or locals that plugged in 110V appliances into 220V outlets.

The thing that blew is a varistor, also known as MOV (Metal Oxide Varistor). And it worked exactly as designed, luckily. This thing is supposed to help against spikes of too high voltage. It does so by shorting the two AC input pins whenever the voltage is too high. Normally such voltage spikes happen only for super short times, which the MOV can withstand without getting too hot (they still wear out after a few such events, though). Now since silly me supplied 220V, and this MOV apparently was a type that trips below this voltage, all that happened was that the MOV shorted the input pins, causing the input current to be abnormally high, which in turn caused the two small fuses in the power supply to trip. After that, no more current flowing. In that process the MOV sadly died, but the rest of the power supply was most likely unharmed.

A quick trip to the underground Guanghua Electronic Plaza (near the computer shops above ground) later, I had the necessary 2 replacement fuses and a suitable MOV. The choice of MOVs >110V and <220V there was very limited, so I went for the only one I could find, a 140V United ChemiCon TNR15G221K:

For the fuses, I went with the same rating as the originals had (220V/5A/slow), only in a round housing vs. the original square ones:

The only other component in the AC side is a 1M Ohm discharge resistor, which despite being blackened by the MOV soot turned out to be still OK.

After de-soldering, cleaning, and soldering of the replacement components the power supply still looks like shit, but works :heart_eyes:


  1. It’s best not to plug 110V devices into 220V sockets
  2. Don’t mess with AC if you don’t know how to do so safely
  3. You could also just leave out the MOV, it would still work. For testing this is fine, but your device is then unprotected from surges (or 220V wielding idiots like me).

I have same problem but I think will just call my landlord to send someone to fix it. :smile:

If your landlord pays for your sillyness, that’s great :+1:

You should watch this guy :grin:


Damn I wish I had this “220V hair dryer in the US” video ready when I had to explain about adapter plugs vs. transformer :praying:

All I know about electrical installation at home:

  1. Fuse boxes here do not work as they are supposed to because Taiwanese do not like them tripping when overloaded so they put a fuse beyond the max so it won’t trip. What can go wrong?

  2. Finding out where the wires go and what power load they carry means stepping through the mirror into another dimension where our logic does not work.

  3. Moreover, what is your bathroom now was probably once the balcony. If a new building, this also applies as they may have modified original plans or workers changed their mind midway.

1 Like

This isn’t rocket science… every electricians knows what amp should go with what wire diameter and all that.

What happens is probably a lot of landlords not wanting to hire a real electrician and so they overload the circuit themselves, and causing problems.

A lot of Taiwanese homes have 50 amps at 220v and it’s not enough if you have more than 2 AC units. If you want to add a dryer, induction cooker, etc. you really need at least 250 amps. Note if it’s 50 amps at 3 phase that’s basically 250 amps at 220v because 3 phase carries a lot more current than single phase. If you have 3 phase there will be a transformer somewhere in your flat for your 110v. 3 phase gives you like 235 v when connected to any of the 2 phases (I measured this) but won’t give you 110 no matter what hence then need for a transformer. So good if your property has 3 phase and you want to use dryers and induction cookers… or industrial machines like mills/lathes.

Some people have the bad practice of wiring the American style outlets with 220v because they are too lazy to wire it for some other plug (like the ones your AC plugs into). And you not knowing (they are supposed to label this, but maybe the label wears off over time) plugs a 110v appliance into 220v which fries it.

I have a welder that runs on 220v and I wire those AC unit plugs into the unit so I don’t do the stupid thing of wiring a standard US style plug with 220v and blow stuff up. Plugging a 220v appliance into a 110v outlet usually just means the appliance doesn’t run properly (like a hair dryer not hot enough) but doesn’t cause any fires.