I’ve only been inspecting a short while and today I did my first house with two prong outlets.
This is probably a dumb question but, what do you do? My three prong tester wouldn’t go into the three prong outlets. How do I know they were even working?
May I suggest a cheater plug or a test light?
Pick up one of the grounding adapters for a dollar. Just verify that is a polarized one. (The hot prong will be smaller than the neutral prong) The tester you are probably using should only show an open ground when using the 3 prong adapter. That will indicate correct polarity.
John, you can check if the receptacle is operable by using volt stick or voltmeter. Regardless, since two prone receptacles are ungrounded you should recommend upgrade to grounded ones (at least those that will be used for computers) or GFCIs as a bare minimum.
Plain ole’ Ticker will work…you can verify it is working, you can determine if it has proper polarity and it will only cost you about $ 15.00-$20.00 bucks.
That’ll let you know if it’s got a hot wire, but it won’t let you know if the rec is functional (open neutral). I’d rather test for polarity with a TIC tracer and plug a test lamp in to verify functionality, if a functional test is what is intended.
If it is an old receptacle, predating the 3 prongers both holes will probably be the same size so how will you determine polarity? It may just be installed upside down 
Don’t forget to note the ones that have lost their tension. Most will be bad in an older home to the point of plugs falling out easily.
Correct me if I am incorrect, but Yuri’s statement regarding a 2 prong being ungrounded is innacurate.
If the system is grounded, and the ground is extended to the box, and the receptacle is mechanically bonded to the box, then the receptacle is “grounded”, no?
My thoughts are that the difference between a 2 and 3 prong is that they are both technically grounded, but the 3-prong allows the system ground to extend to the applicance it connects to, if a ground plug is required.
Cheater plugs should have the green wirre, or green metallic thingie, securely fastened via center screw on the receptacle cover, otherwise using them is a no no.
So, assuming the system is indeed “grounded”, am I right or wrong here?
I will disagree merely to draw a response as my curiosity runs concurrent with yours.
Joe, old houses that have two prong receptacles most likely were wired with old cloth-covered wiring that did not contain ground wire. How could the outlets be grounded?
Yuri,
1930-40 Homes wired with BX are quite common.
Joe, I agree with BX, but this is expensive and was not so common here. Anyway, two prong receptacles are outdated to comply with “modern days requirements”
Geographic differences noted.
While BX may not have been commonplace in your area, BX was quite common in this area.
Yuri,
If the receptacle is not damaged, and the system is indeed grounded (easy to determine when the dead front cover is removed), and the 2-prong is grounded, then what is the problem? Is the receptacle defective, or not?
Also, what does “outdated by today’s requirements” mean? I submit that a majority of today’s plug-in electrical devices do not require a system ground (except for vacuums, cleaning machines, some other motor-driven appliances, etc). Some double-wound electric motors no longer require it, either. I’m not poo-pooing the idea, by the way. I’m going back to the initial question and Yuri’s statement.
As to any assumption whether a ground conductor is present in the branch distribution cable, this is the reason the dead front cover is removed. As I stated, we’ll assume that the distribution system is grounded. That was what my comment was directed at. There are some clowns who take a cable, absent of grond conductor, and bootleg the neutral. Just because it has a “grounding” receptacle doesnt mean it’s correctly wired.
Now, (again) the original question went to testing. If you have a cheater plug (which is not a way to cheat, really, but a way to extend the system ground to a device that requires it), then a wiring tester is adequate. I touch the green wite to the center screw on the receptacle cover…
I’ll bet that some of these original systems and receptacles are sometimes safer then when Harry The Homeowner strikes.
Think about this. Most electrical appliances today do not have a three prong cord. Only metal case appliances, or computers which need an equiptment ground to shunt surges to. A wiggy is still in my tool box, cheap, effective. Back in the old days we had a hot and a ground, no neutral. Now, the neutral and the ground wire generally go to the same bus bar in the breaker box. Is the neutral grounded? Of course it is. But… it is not called THE Ground. If whatever you have plugged in to the outlet does not have a three prong, grounding cord, you do not need a ground.
Joe, what I mean is that neither NEC nor CEC allow installation of two prong receptacles in today’s construction. My reply to the initial post was based on the assumption that two prong receptacles were wired with old cloth covered two conductor romex. In this case you either need a dedicated ground for computer equipment or GFCI. If there is a system ground and the outlet box is grounded by some means, then there is no need for replacement of two prong receptacles unless one needs three prongs. And yes, you are right here :mrgreen:
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Most the two hole ungrounded outlet systems I run into are supplied by two wire cable, no armor, how can the box possibly be grounded?
Will,
The system you are describing is one of ungrounded receptacles. The original question went to how to test a two-prong. Yuri chimed in that a 2-prong isnt grounded. Playing Devil’s Advocate, I pointed out that the presence of a 2-prong receptacle doesnt necessarily mean that the receptacle is ungrounded. That determination is based on examination of the system, itself. Like cloth covered cables with no ground, versus BX or Romex, with ground path included.
Although a lot of places ignored it, the GI Bill/FHA required a grounded wiring method in the 50s. That was either AC cable or the reduced size Romex. That still got installed with 1-15 receptacles and the only thing grounded was the box. It did allow the adapter to work though as long as the device was made up tight to the box.
I know they actually had GI/FHA inspections in the DC area. That probably didn’t happen out in the hinterlands. In 1971 the house I bought would not pass the GI inspection. (Aluminum wire)