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I just rented an apartment (Colorado, for what it's worth RE code) that has 2-pronged outlets throughout the place except for two GFCI's, one in the bathroom and one in the kitchen.

I bought the $.30 2->3 adapter and screwed that extension piece of metal into the faceplate, and then used a cheap 'tester' to see how the outlet was wired (it has 3 lights, and they come up in combinations to indicate no ground, no hot, no neutral, etc). Each outlet I tested was 'no ground', so the boxes themselves aren't actually grounded.

I asked the landlord about this and they said 'we asked at Home Depot, and they said it's no big deal, just use a surge protector'. I don't know much about wiring/circuits etc, but this seems like shady advice given the landlord's interest to not rewire. I am a professional programmer owning a good amount of expensive hardware that 'asks' for 3-prong outlets to be used when plugging it in.

My question: What are the potential hazards (to myself and my equipment) of using a 'falsely' grounded 3-prong plug with my equipment? Is this something I should press the landlord on for code issues? (It may have been grandfathered in, the building is old but was recently redone).

Thanks for any input and advice.

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My primary concern would be for your safety with the circuits with GFCIs. I find it hard to believe that just those two circuits would have been upgraded to grounded cable in a remodel, and I can't see any way that a GFCI could work with ungrounded cable. Test that the GFCIs work correctly on their own. Does your receptacle tester also have a GFCI test function? If so, use it on the GFCIs too.

It's OK to have two-prong outlets if they're not grounded: see this answer to this earlier question for more information, but a surge protector simply prevents sudden changes in supply voltage from reaching the equipment it's protecting, be it on live, neutral or ground; it doesn't do anything to provide a good, stable, ground level where one didn't previously exist.

Electronic equipment often likes to have a stable ground level as a reference point. Under normal circumstances, the ground conductor in NM cable doesn't carry any current, so it's all at the same electrical potential as the ground spike outside your building. Without that stable level, a piece of equipment's internal "ground" can vary. This usually isn't a problem internally within a single piece of equipment, but can cause problems if electrical signals are shared between two pieces of equipment: mains hum in hi-fi systems would be one example of this. You can mitigate the effects by keeping related equipment close together to minimize the amount of electrical wire between them (like plugging them into the same duplex receptacle) but, depending on exactly what equipment you have, you may still run into problems.

As far as code compliance, permit applications and inspection results may be a matter of public record (they are in my locale), so you could do some research into what was done during this remodel.

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    GFCI works without ungrounded cable because its purpose is to interrupt a ground fault by opening the circuit, not to ground power. It measures flow in and out, and when the delta exceeds a limit, it opens the circuit to stop the flow of current entirely. The assumption is that the missing current was diverted across your heart, and you'd appreciate living another day. – Jeremy W. Sherman May 15 '12 at 23:35
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    Seconding @JeremyW.Sherman , GFCI does not require grounding, although they are supposed to have a label reading "No Equipment Ground." – Craig Dec 7 '14 at 23:28
  • @JeremyW.Sherman did you mean "GFCI works without grounded cable"? – ijoseph Aug 25 '18 at 21:37
  • @ljoseph: Yeah, pretty sure I hesitated between "with ungrounded" and "without grounded" and wound up botching it. GFCI will work, ground or not. – Jeremy W. Sherman Aug 28 '18 at 13:25
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I'm not a professional electrician and won't ever argue that the third wire is useless or anything like that, but where I live two-pronged outlets are the only choice in houses built before perhaps 1980 and I've been living in such house for many years and I know dozens of people who have been living in such houses too and I've never heard any equipment ever died specifically because of using a two-pronged outlet. Don't forget mind that when something breaks the owner brings that unit to a service shop and the service shop would be glad to say "oh, you used a two-pronged outlet, that voids warranty, goodbye" yet that never happens.

Your primary concern should be your own safety - like if insulation gets damaged somewhere and you hold the damaged unit with one hand and touch a steel water pipe with another.

  • Actually, according to my older brother (late 50s), when something breaks these days you 'darn' it, which means holding it over the trash can, regretfully saying "Darn!" then letting go. This costs less than the fuel to get to the "repair shop" if you can even find one. I see lots of closed electronics repair shops. Even the local Radio Shack went away. Darn! – user50401 May 6 '16 at 1:33
  • @nocomprende Not while the warranty is still in effect. – sharptooth May 6 '16 at 6:59
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There is probably no danger to your equipment, but there is serious personal danger. Without a separate path to ground (the third prong), any equipment malfunction that causes the frame or chassis of the equipment to become energized (live) may represent a lethal shock hazard to anyone who touches the unit. This current leakage may not be enough to trip a breaker, and it may only give you a “tickle” when you touch the equipment when you are dry, wearing rubber-soled shoes, and standing on wood. But touch the same equipment when you just got out of the shower and are in your bare feet, and you could become a statistic.

A surge protector has nothing to do with grounding. It merely clamps the line voltage if it rises above a preset level because of power company problems or a lightning strike. You should always have surge protection on all sensitive electronic equipment, such as computers, TVs, etc.

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    That's partly true. In order to be shocked one has to become a conductor between a unit and something grounded. So if you just stand on dry floor and don't touch anything like a water pipe you'll not be shocked most of the times. This explains how people live dozens of years in houses with two-pronged outlets and never get shocked (see my answer for the background). – sharptooth Feb 7 '11 at 8:04
  • Put another way: a surge protector will protect your devices from damage and malfunction. It will not protect you – this is the job of grounding and GFIs. – user149408 Apr 8 '16 at 7:47
  • Much consumer equipment is plastic-cased with no exposed metal these days for this reason. In a wall switch, only the screws holding the cover plates are grounded (or not) and you can use plastic screws for this if you wish. – user50401 May 6 '16 at 1:30

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