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I'm fairly competent as a DIYer, but I don't have the ability to dig in to this problem directly yet.

I'm considering buying a very historic house (more than 180 years old). The wiring coming out of the breaker box (and it is breakers) appears to be relatively modern. That is, it has plastic sheathing rather than a paper-like stuff that I have seen in some older houses.

However, all of the outlets I saw during the tour were un-grounded three-plug outlets. That is, you could plug three lamps in with out needing a splitter. However, nothing had a ground pole. (I'll post a picture if I ever find one).

Picture from electrical-contractor.net

Does this indicate some complication (beyond lack of ground) that I should be aware of with the wiring in the wall?

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    Ecnerwal: Thanks for finding that. This is exactly what kind of outlet is all over the house. – Elros Aug 5 '15 at 15:24
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You, or your house inspector, would want to investigate if the "modern wiring" makes it all the way to the outlet boxes (in which case a simple replacement will get you grounded 3-prong outlets) or if it stops short and leaves you with old ungrounded wire to the actual outlets (in which case you'll want to lower your offer by several thousand dollars to pay for the rewiring.)

The triple outlets could just be a fashion choice, but you need to know to make a reasonable offer on the house.

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  • Of course. However, I won't be able to dig in to the wall to see. I'm more concerned about relatively modern wiring at the panel being converted to something like knob-and-tube in the wall. – Elros Aug 5 '15 at 15:31
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    Those triple outlets may still be technically legal. There are some even older outlets similar to that that had 5 sockets. You also want to make sure that the wires aren't made of aluminum. If you see 3 copper wires with modern color codes (red, black, and bare wire) then you are fairly safe as long as the wire is continuous and goes directly to the panel. – Jason Hutchinson Aug 5 '15 at 20:30
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    Digging into the wall is not required. Simply opening up the outlet boxes and inspecting the wire coming into them will generally tell the tale, and if the seller won't let you or your home inspector do that, it's a huge red flag (i.e., assume the worst and lower your offer accordingly if you still think you want to buy the place, or just walk away and find a different house.) – Ecnerwal Aug 5 '15 at 20:54
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    If the outlets are like they are in the picture, then they are polarized plugs. You can tell because one side of the plug is slightly larger than the other. Use a non-contact voltage tester to test if these outlets are wired properly. To test for polarity, take the circuit tester and test the hot side of the plug (the narrower one) and see if you read a voltage. Then test the wider side (neutral). You should get a reading from the hot side, but not the neutral side. If both are hot, then it is incorrect. After that you can use a multimeter to test the line voltage. It should read around 120v. – Jason Hutchinson Aug 6 '15 at 20:04
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If the outlets are all 2-prong openings, then obviously the sockets are all ungrounded which is a bad thing. Running grounds to all the outlets in the house and replacing the sockets with grounded 3-prong sockets could be annoying.

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    I'm a little curious why an answer gets 3 down votes and not a single comment on why. I don't see that this answer is so farfetched as to earn -3. Anyone care to backup their down votes? – mjohns Aug 5 '15 at 21:20
  • I didn't down-vote, but I considered it. The question already specifies a concern over lack of ground. The question requests what else might be wrong. Your response only repeats a concern already mentioned in the question. – Elros Aug 12 '15 at 19:21

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