Is My Outlet Grounded? How to Check Using a Multimeter

[Pengwuino]

This is probably too silly of a question to ask in one of the actual engineering forums so i threw it here. How can I tell if my outlets are grounded? I finally got a decent surge protector and when I plugged everything in, the little light that says "Not grounded" came on :(. I checked all the outlets in that set of 4 outlets and none of them looked grounded. How can I check? I have this lil multimeter from radioshack I got long ago that's rated 500V max, 200mA max which i doubt should be used haha. Maybe my surge protector is defective.. hmmmmmm!

 

[Evo]

http://www.greatinspector.com/faq-elec-unground-outlet.html

 

[Loren Booda]

Thanks for the resource, Evo! I'm of the older persuasion.

 

[Pengwuino]

Oh Evo you have so little faith in me :P The outlets in question are 3-pronged, except when I connected this new surge protector, it said the outlet wasn't grounded. I need to figure out if the faceplate is misleading and has 3-pronged outlets but having no actual ground.

 

[Astronuc]

This is probably too silly of a question to ask in one of the actual engineering forums so i threw it here. How can I tell if my outlets are grounded? I finally got a decent surge protector and when I plugged everything in, the little light that says "Not grounded" came on :(. I checked all the outlets in that set of 4 outlets and none of them looked grounded. How can I check? I have this lil multimeter from radioshack I got long ago that's rated 500V max, 200mA max which i doubt should be used haha. Maybe my surge protector is defective.. hmmmmmm!

It's not a silly question. It's probably worthy of general engineering. I found older outlets in our house that were not grounded, or were improperly grounded, and it is a violation of current code.

If there are only two wires in the line (usally one white and the other black) on the back of the receptacle, then it is not grounded. There should be a third line, green insulation or bare copper, that should be grounded.

http://en.wikipedia.org/wiki/Ground_and_neutral
http://en.wikipedia.org/wiki/Electrical_wiring_(United_States )

The neutral line (white) is sort of ground (I believe the term is floating ground) but it would grounded at the circuit box or through the line, as opposed to a lower impedance ground that is supposed to be wired directly to the ground (local earth) - independently from the circuit breaker box.

The wiring in my house is black (hot) and white (neutral) with bare copper ground wire.

 

[Chi Meson]

Use your meter in continuity check mode. Put one probe in the ground hole and the other in the neutral slot (which should be the WIDE slot. The narrow is "hot.")

If it is grounded, then there should be a continuous circuit, since ground and neutral are both connected to the same ground.

 

[Cyrus]

You should use the well proven method of the ground-o-meter.

Simply unbend the device and probe the outlet for a positive indication. You can already see it detecting active magnetic fields in this picture.

 

[Pengwuino]

Well I just woke up after checking the outlets, I'm not sure what happened. All I remember is some sparks and for some reason I decided to take a nap?

My arm feels numb as well and something smells like burning flesh. Maybe a dead animal in the walls.

I think I'm going to call an electrician and exterminator tomorrow to fix this.

 

[Cyrus]

Well I just woke up after checking the outlets, I'm not sure what happened. All I remember is some sparks and for some reason I decided to take a nap?

My arm feels numb as well and something smells like burning flesh. Maybe a dead animal in the walls.

I think I'm going to call an electrician and exterminator tomorrow to fix this.

You idiot! you put the wong side of the ground-o-meter in the socket. Do it again with the other end...jeez. Do I have to do everything around here for you? If you do it right, it should read 1.21 jiggawatts.

 

[dlgoff]

[PLAIN]http://www.delstat.com/images/Outlet_Tester.jpg

 

[Office_Shredder]

You're going to call an exterminator to take care of the dead animal? Maybe you should sleep on it

 

[Saladsamurai]

<snip> ... If you do it right, it should read 1.21 jiggawatts.

OOoooh! Somebody got the brand new Jay - Z big jigga-man multimeter for christmas! Does it have the jigga-who setting? Or just jigga-watt?

 

[Office_Shredder]

The new ones come with a jigga-please extension that performs oral sex on you as you read the voltage.

 

[Cyrus]

I have no idea what you kids are talking about...I feel old. Thanks, jerks.

 

[Saladsamurai]

The new ones come with a jigga-please extension that performs oral sex on you as you read the voltage.

Oh jesus...

I have no idea what you kids are talking about...I feel old. Thanks, jerks.

Don't worry Cy, if it makes you feel any better, I am sure that I have a few years on you

 

[Ivan Seeking]

Just for the record, in the US, a [white] neutral wire is grounded. A "floating ground" generally refers to a "defined" ground that is not Earth grounded. We use this frequently in industry for noise immunity in signal circuits.

So a neutral wire IS grounded. However, while a neutral wire normally carries current, a green ground wire only carries current in the event of a failure. That is the only real difference between the two.

 

[Danger]

Something smells like burning flesh.

Are you sure that it isn't burning fish? That would be explainable.

 

[Moonbear]

Well, the easiest and most obvious thing to check first is to just unscrew the outlet from the wall and look if there's even a grounding wire attached. I have seen houses with 3-prong outlets installed, but without any grounding wire attached (it's clearly a code violation, but people do it anyway).

If you do have a grounding wire attached, it's time to nose around and see where they go if you can. If you're in an older building, sometimes wires are grounded through the pipes...until someone unknowingly replaces a section of pipe with PVC.

Another obvious place to look is outside where your electric service enters the house and see if there's a separate wire literally running into the ground.

If you find out that your outlets are not grounded, you have a few choices. You can switch them to two-prong outlets (probably the least desireable option). If you find that your grounding wires are run through the pipes and there's a PVC section, you can run a bridge wire across that section to reground it (check on your local electrical codes first, in case this is no longer allowed...while it used to be common, the idea still gives me the heebee jeebees). Anything beyond that, and you should probably employ an electrician to remedy the problem, just so you don't invalidate any home fire insurance by attempting to do it yourself, even if you know what you're doing (and since you're asking the question, I'd venture the guess that you probably don't know what you're doing on this one).