Why is this device shorting out my power?
May 18, 2015 7:47 PM   Subscribe

Why would using an American electrical device on European voltage cause it to short out circuits at home when I plug it in again after coming home to the US?

I recently traveled to Europe from the US and plugged in my, um, personal massager in my hotel room using a plug adapter. It immediately shorted out power to the room. Oops!

I then returned to the US and plugged it in again -- where it then ALSO shorted out the power to my room. It had never done this before.

Now I'm really curious -- what is occurring on an electrical/circuitry level to explain this behavior?
posted by anonymous to Science & Nature (8 answers total)
 
My first thought is that it has nothing to do with any Euro/U.S. difference - it's simply that your personal massager and/or the power cord is broken. There is an electrical connection being made somewhere that should not be, causing a short circuit, which in turn will trip circuit breakers/blow fuses.
posted by soundguy99 at 7:58 PM on May 18, 2015 [3 favorites]


If it's tripping the breaker, it's drawing more current than the breaker is rated for. Most likely it's got some sort of dead short inside it. Considering that it happened when you first plugged it to a 220v circuit, that's probably where the problem came from. Was your plug adaptor actually a transformer (something that changes the voltage), or just a plug adaptor? If it was just a plug adaptor, that's your culprit right there. Twice the voltage your device was expecting has a funny way of melting electronics.
posted by mollymayhem at 7:59 PM on May 18, 2015 [6 favorites]


Personal items with electric motors are generally not built to deal with different voltages; using an adapter that doesn't step down the voltage will do bad things to it. The most well-known plug-in personal massager is explicitly 110V only. Even one that claims to be multi-voltage but is sold in the US may be taking certain liberties.
posted by holgate at 8:21 PM on May 18, 2015 [1 favorite]


It immediately shorted out power to the room.

If you're lucky, that will be because your device has an inbuilt surge protector which has responded to gross voltage overload by failing safe, meaning that from the time of failure onward it presents as a short circuit in order to trip the supply breaker and protect downstream components from further insult.

If you're not so lucky, it will be because the device's motor is now a melted lump of slag that's done essentially the same thing by accident.
posted by flabdablet at 9:47 PM on May 18, 2015 [1 favorite]


If you're lucky, that will be because your device has an inbuilt surge protector which has responded to gross voltage overload by failing safe, meaning that from the time of failure onward it presents as a short circuit in order to trip the supply breaker and protect downstream components from further insult.

I would also guess that it died as soon as it was plugged into twice its rated voltage in Europe and now has a short circuit. 99% chance it's dead, throw it out. The rest of the explanation quoted above is wrong - failing safe is to fail to open circuit, not short. As to how a short circuit would protect downstream anything, I'm not even going to try to pick that apart...
posted by deadwax at 1:01 AM on May 19, 2015 [4 favorites]


For most electronic devices, the US uses 110volts and Europe uses 220volts. Most devices today are made to be compatible with either voltage. However, if the device is somehow stuck on wanting 220V, it might be trying to draw to much power, and an AFCI breaker in the US could easily be reading that as a dangerous surge, and trip the breaker.

I am an electrician, not an electronics guy - so this is a guess at what your device is doing, but that is my first thought.
posted by Flood at 4:06 AM on May 19, 2015


failing safe is to fail to open circuit, not short. As to how a short circuit would protect downstream anything, I'm not even going to try to pick that apart...

Surge protectors are generally wired across the supply mains, from active to neutral. Their job is to protect the connected equipment from excessive voltage (often temporary - hence "surge") and they do that by lowering their own resistance enough to divert the bulk of the surge current after detecting excessive voltage across their terminals.

Some types do it by lowering their own resistance so much and so quickly as to simulate a switch connected directly from active to neutral, effectively mimicking a short-circuit electrical fault and protecting the connected device by crowbar action. Others conduct just hard enough to limit the instantaneous voltage that appears across their terminals to some presumed-safe value, generally relying on the short duration of surges and the inductance of the supply wiring to limit the amount of energy they themselves need to absorb.

If a surge protector fails it is far safer for it to fail short than open, because if a surge protector fails open it effectively disappears from the circuit altogether and might as well not be connected at all.

A surge protector suitable for equipment designed for a 110V supply would almost certainly fail, and fail hard, when connected to a 220V mains; the amount of energy that a shorted surge protector would absorb in the time between triggering itself and blowing the breaker would be about four times what it would see if triggered by a spike on a 110V mains.

The main reason I thought of a failed crowbar-style surge protector, rather than immediately assuming simple motor burnout, is that it might be possible for such a surge protector to fail short without emitting the pungent and inescapable stink of properly burnt-out electronics or motor windings, of which no mention was made in the question.
posted by flabdablet at 6:22 AM on May 19, 2015


Ah, I read downstream components to mean other appliances plugged into the same circuit, not downstream components of the same appliance, which left me scratching my head. I also thought you meant the appliance failing to a short was a safety feature generally, whereas I suspect you'd agree surge protectors presenting a short to the mains are very much a not so nice compromise and appliances failing to an open circuit would be preferable. I see what you mean now, sorry.
posted by deadwax at 6:25 PM on May 19, 2015


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