Changing 2-prong outlet to 3-prong?

[BigToque]

I've got 14 plug outlets I want to change from 2-prong to 3-prong.

I've opened them up and they've all got hot/neutral/ground wires.

The ground wire is screwed into the metal casing and the hot/neutral attach to the plug.

Can I just wire in a 3-prong in place of the 2-prong and keep the ground wire connected to the metal casing? Or do I have to physically wire the ground wire to the new 3 prong plug?

 

[Demon-Xanth]

If the ground wire is indeed ground, then you can just wire in a 3 prong and consider yourself very lucky. It's better to attach it to the lug, though really they're usually all connected together anyways.

The way I would do it:
Buy one outlet.
Get an outlet tester.
Wire that one up.
Check it.

If it's good, (two lights, no red) then you're good to go for the rest. If not, you'll need to figure out why and re-evaluate what you have ahead of you.

<-- rewired virtually his entire house last spring due to the lack of grounds.

 

[DrPizza]

If you have a voltmeter, check to see that the voltage between hot and neutral is the same as between hot and ground. If so, you're good to go. They sell pigtails at hardware stores, if you don't want to bother cutting & stripping wire to ground the outlet to the box. (A ground screw with a wire already attached.)

 

[TheSiege]

If your metal box is indeed grounded then you are fine, push come to shove a GFCI will give you the protection of a grounded receptacle although some equipment do not function correctly without a ground. But I doubt you would have anything like that, just certain motors and high end computer stuff.

<-----Electrician

 

[BigJ]

If you buy receptacles listed as "self-grounding" and the metal box is indeed grounded, you do not have to connect a pigtail from the box to the receptacle.

If you buy standard receptacles, then you will have to run a ground wire from the box to the receptacle screw.

If using NM cable (Romex):
Take note, you can only land one wire under the ground screw that is currently securing the ground wire to the metal box.

If using Armor-clad cable (BX is what it is most commonly referred to as, although this is incorrect):
Make sure that the wire going to the ground screw in the box is not a thin silver looking wire. This is actually a bonding strip that runs inside the cable used to provide a low impedance path. If this is the case, the box may still be grounded due to the nature of AC cable, but you would want to remove this silver wire and put in a new ground screw + wire to the receptacle if using regular receptacles.


Article 250.146 in the NEC is the relevant article, specifically 250.146(B).