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We have one room in our house that only has two-pronged receptacles and they are not grounded.

I've read that you can install a GFCI outlet on a non-grounded junction box and that would be okay.

My question is, is it really safe?

Can I plug in a surge protector and then plug in my laptop and smart phone and not worry about electrical issues?

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An ungrounded GFCI is possibly NOT adequate for sensitive electronics.

You need to check your equipment. If your laptop power supply says that it requires a grounded receptacle, take it seriously:

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GFCI's Protect Humans From Electrical Shocks (Grounding is about other stuff)

The primary purposes of grounding are protection from overvoltage (lightning strikes, weird events at the local power substation), voltage stabilization (grounding means connected to the earth, and the earth is the closest thing to a stable reference voltage in most places), and it does also provide a degree of human protection.

You can connect a 3-hole GFCI (or a regular 3-hole receptacle downstream from a GFCI) and it is perfectly safe for living creatures like you.

The GFCI is all about human safety. It trips if there is any imbalance in the voltage on the hot and grounded ("neutral") conductors. The voltage on both wires should be identical when a load is attached. If there is a differential, it's because current is leaking somewhere else. If enough current is leaking through you (particularly through your heart) it might be your last day.

These ungrounded GFCI receptacles, while perfectly safe for people, should be labelled "No Equipment Ground" because they are NOT grounded, and therefore are not necessarily safe for all equipment.

Some equipment is sensitive or highly-sensitive to grounding

Grounding keeps electrical surges from blowing up your appliances and electronics. Grounding helps ensure stable voltage for those sensitive electronics, and it also reduces hum in electronics, and more. At least some surge suppressors shunt current to the grounding conductor (they also absorb current regardless of grounding), and so on.

For example, if your laptop power brick has a 3-prong plug, chances are pretty good that if there's a power surge, it will divert the surge down the ground wire away from your expensive laptop. Unless there's no ground wire.

Look at it this way; if you plug a $20 hair dryer with a three-prong plug (this is an analogy, I have no idea if there actually are any hair dryers with three-prong plugs) into an ungrounded GFCI-protected circuit and something happens to the hair dryer, well, no foul, right? You didn't get electrocuted, and you can throw the hair dryer out and replace it easily enough or suffer the inconvenience of waiting for your hair to dry if $20 doesn't fit in the budget this month.

On the other hand, if you plug a piece of expensive, hard-to-replace equipment into an ungrounded receptacle, well you've been warned. Your warranty will probably be void if the manufacturer determines that the equipment wasn't grounded. If it's insured and the insurance company determines that it wasn't properly grounded, they'll probably deny your claim. If you're an inventor and the equipment is the result of years of hard thinking, sweat and penny-pinching, you're just plain starting over.

But if the receptacle is protected by a GFCI (fingers crossed the GFCI doesn't fail as they occasionally do), then at least you won't get electrocuted.

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You can get a 3-prong plugin at locations that only have 2 wires by installing a GFCI. There should be a label in the box with the GFCI that says "No Equipment Ground" which must be applied to the face of all 3-prong outlets protected by the GFCI including those downstream.

It's perfectly safe for your power tools, plug your drill, etc in as much as you want.

A surge suppressor plugged in at that location will NOT work. The wiring fault light on the unit will be on, because the is no actual ground which it need to suppress a surge.

Your smart phone probably isn't 3-prong.

Edit: (thanks to @craig in comments) Laptops with a ground pin should not be used in a GFCI labeled as "No Equipment Ground". There are varieties that may need Equipment Ground for effective static discharge. I can also find examples where I don't believe that's the case, but it's better to say laptops should not omit the equipment ground.

"Other" electronics may vary by what and why it's a 3 prong plug. The consideration is that the human safety from electric shock is covered by the GFCI, if however the device needs ground to dissipate static charge, or has built in surge suppression, it should not be used in an outlet marked "No Equipment Ground".

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  • I'm confused. Doesn't 3-wire mean hot, neutral and ground? I don't have a ground wire to those receptacles. – milesmeow Dec 10 '16 at 15:20
  • Corrected the typo sorry @milesmeow – Tyson Dec 10 '16 at 15:20
  • You're right about the brick. The laptop I have has a brick that converts between a 2-prong plug and a 3-prong. – milesmeow Dec 10 '16 at 15:26
  • That is NOT necessarily always true about laptop chargers. – Craig Dec 11 '16 at 5:03
  • @craig I did include the word "modern" because I can go find "other" examples in our companies hardware boneyard of retired equipment--- however in the past 8-10 years I don't know of anything, if you have examples please link, so I can get the answer updated. – Tyson Dec 11 '16 at 5:55

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