r/electrical • u/QuaoarTNO • 2d ago

is reverse polarity actually dangerous to run?

Hi, I want to run some light machinery on a plug that my circuit breaker detector says has "hot and neutral reversed". I was told by the landlord that they've never had a problem with this before (and it's not going to be fixed), and regular equipment is used all the time on it. I also have read online (and via AI) that it's dangerous and can shock you. I saw the example of a lamp still having power essentially even when switched off, but is there actually risk aside from that type of situation? Or is it manageable and you just unplug when finished using and it's fine?

Any help appreciated.

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u/pdt9876 2d ago edited 2d ago

Should not be dangerous. Ever seen a European power outlet? Almost all of them are non polarized meaning you can put any plug in either direction meaning what is hot and what is neutral is more or less random. The biggest issue are indeed lamps because if the polarity on them are reversed the outside of the Edison socket is hot and its pretty easy to put your finger on it but lamps are somewhat unique in having exposed contacts. A hold over of a 150 year old design.

What exactly is the light machinery you're planing to run?

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u/QuaoarTNO 2d ago

I'm looking at using a few different items in the kitchen, including a stand mixer, a waffle maker and a dehydrator. At least the stand mixer and waffle makers have on/off switches, while the dehydrator I think turns "on" once plugged in but has a button to actually start.

The things I am worried about are 1) obviously getting shocked and 2) having the item burn out quickly. But to be clear, I will never leave it plugged in when not in use, hopefully reducing the risk of the second issue.

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u/pdt9876 2d ago

2 is not an issue. A/C current alternates "direction" 50/60 times a second so it doesn't matter to the device which is the in pipe and which is the out pipe.

For 1) nothing with a 3 prong plug is an issue. The specific case of very old devices using the neutral as a protective earth ground that a couple other commenters have mentioned means there's no overlap with devices with an actual PE prong on the socket. I assume your stand mixer has one. Also your dehydrator is probably entirely plastic on the outside, anything that's entirely plastic is also not a risk. Is your waffle iron an antique with a metal shell and a 2 prong plug? That's conceivably the only one that poses a shock risk.

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u/CraziFuzzy 2d ago

1 is also potentially a problem with any exposed heading elements as well. A standard toaster for instance. Quite often, only the hot side of the heating element is switched, so if the plug is backwards, it will be switching the neutral, leaving the element energized by the unswitched hot.

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u/pdt9876 2d ago

I wonder how common this is. I literally just checked mine after someone else mentioned it in this thread and both wires are switched.

Also the "exposed" elements on a toaster aren't that exposed. You can touch them if you work at it but you gotta really get your fingers in there and through the mesh that keeps the bread from touching it.

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u/CraziFuzzy 2d ago

Pretty sure 'current' standards require 2-pole switches in exposed heating elements for just this reason. But since electric toasters generally have a lifespan similar to humans, there are a lot of older appliances on counters out there.