Reverse polarity

During a recent inspection, my electrical tests revealed several electriical outlets with revese polarity. How serious is this and what kind of problems could ths cause?

David, I always report this as an Issue with the electrical system and recommend a licensed electrician properly rewire these outlet(s). Under certain circumstances it could present a shock hazard, so it could be very serious !


Thanks for the info- I’ll pass it along


Thought I would add this;

Hot / Neutral reversal, called reverse polarity, is probably the most common error you’re going to encounter. While few (if any) electrical devices care much whether the current runs left to right or right to left, almost every electrical plug made in the past few decades is polarized for safety’s sake. They can only be plugged into (modern) outlets in one orientation, which is designed to ensure that if there are any electrical shorts in the device, exposed metal parts don’t carry the current. Wall sockets that have reversed polarity are considered an electrical shock hazard, which is why they’re noted on pre-purchase house inspections. Fortunately, the condition’s fairly easy to fix: all you have to do is reverse the black and white wires.

Marcel :slight_smile: :smiley:

Think of a simple lamp. Instead of the button at the bottom of the socket being live the metal sides are live.

A modern gas furnace will not function with reverse polarity. I haven’t seen anything else that cares, but I am sure there are some other appliances. Regardless, it is still a hazard and should be repaired.

Most lap-top/notebook…have polarity protection but may blow an internal fuse when used on a reversed polarity receptacle

BEST to check the receptacle before plugging in your equipment on-site…you never know…

Same here. I ran into this same situation with my last two inspections, one a trashed foreclosure and the 2nd a very nice home. Reported both and recommended a lic electrician.

Most lap-top/notebook…have polarity protection

Didn’t think this was an issue since it goes through a transformer first anyway.

Reversed polarity can be dangerous because many appliances will operate properly even though the supply wires are not connected in the proper order. Traditional reversed polarity occurs when the black (ungrounded) and white (grounded) conductors are reversed. A shock hazard may not exist, but other mechanical hazards can occur. If an internal fault should occur in the wiring, the equipment would not turn off when the switch is released or would start as soon as the supply cord is plugged into the improperly wired outlet. This could result in very serious injury.

and this…

I don’t see why a laptop power supply would care what the polarity is on the input. They’re typically rated for 100-240 VAC meaning that they will work with or without a neutral.

Never heard of that either.

It’s ash backwards report it.

Great picture, Marcel. Most people will understand that.

Yes but in most the screw portion is insulated from the outer metal shell and shade support.

BUT not all.

I has one last year where the metal floor lamp was “hot” and not insulated as pictured.

The screw portion may be insulated from the outer metal shell and shade support *but the bulb **exposed *metal part while being screwed (in or out) is not

That’s usually the issue, where you could contact the shell of the lamp while changing the lamp. And the graphic isn’t really the best for describing the danger of reverse polarity at the receptacle because it actually depicts the lamp socket as mis-wired. If the receptacle were reverse wired the lamp shell would be hot even with the lamp switch in the off position.

Some electronics will have internal fuses on the hot side and not the neutral, therefore, if the wiring is reverse the fuse may not blow and the equipment gets damaged.

Also, Laptop power bricks are rated for 120-240, the 240 being European voltage and not two phase.

re laptops, you are confusing DC and AC, if you check your laptop’s AC cord you will probably see that it has two equal width prongs, meaning you can plug the cord in any way at all, you can also plug it into 240 volt. The AC goes through the power supply (the black plastic brick) that converts AC to low voltage DC, which if connected wrong, can indeed allow the the magic smoke that makes it work to escape.