2 prong to grounded outlet question

eoren1January 7, 2010

We are purchasing a house built in the 1940's with 2 prong outlets throughout. As part of the remodel, we are upgrading the service to 200A circuit. The electrician also quoted me a $20 charge to change out each 2 prong outlet to a grounded 3-prong one. I'm wondering how difficult this would be for me to do. I have done basic things like installing ceiling light fixtures.

Help/advice is greatly appreciated.


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I hope he doesn't plan on pulling out the 2 prong and replacing it with a 3-prong with no additional work. That would be far from code. At the minimum you would have to have a GFCI put in at the 1st point in each circuit and mark all the outlets with a sticker that says "GFCI protected no equipment ground" or put a GFCI breaker on each affected circuit with the stickers. I'm sure he is not running a grounding wire or rewiring each outlet for $20 each unless he profits $5 to $10 per hour. There are some not so smart electricians still out there changing them out with no additional work that think what they are doing is ok or just know it is not part of the permit and wont be inspected.

    Bookmark   January 7, 2010 at 11:39PM
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If he is indeed charging $20 for each receptacle, he is most likely only replacing the receptacle and NOT actually running a ground.

Adding a ground is MUCH more involved and generally can cost between $100-$150 PER receptacle. That's because the electrician has to pull a NEW 14/2 wire as well as a new receptacle. All the existing wiring would be abandoned in the walls since they are now useless.

    Bookmark   January 8, 2010 at 12:17AM
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Thank you both for posting and I'll have to profess my ignorance here. The guy told me that the outlets were 'groundable' and would not require rewiring or adding a ground. I think the wiring is Romax. I'll email him to ask specifically what is entailed in changing out the outlets.

    Bookmark   January 8, 2010 at 7:29AM
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If he is a professional and he is only charging $20 I would have to assume(bad idea) that he has already determined that there is a ground present in the box.
If not then maybe he is installing GFCI breakers in the panel on those circuits. If he does that then it is simple to just change the receptacles and lable them not ground present.

You need to ask him exactly what he is going to do. Are you going to get actual grounded receptacles or just 3 hole receptacles?

    Bookmark   January 8, 2010 at 8:15AM
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The best case scenario would probably be if the original 1940s wiring was metallic sheathed (e.g., BX, AC or MC..whatever you want to call it) or was run in metal conduit. In that case, it's possible that your outlet boxes are readily "groundable". But if it is actually Romex from that era, as you suspect, it's unlikely that it has a ground wire present.

I'd be surprised if a proposal to replace outlets for $20 a pop would include individual GFCI receptacles. They cost around $15 apiece retail, although a pro buying in quantity with a trade discount may be able to get them for a few bucks less. That certainly doesn't leave much room for labor.

By all means, ask your electrician exactly what he would do, what is included in the price, and how he's determined that the outlets are "groundable".

    Bookmark   January 8, 2010 at 10:47AM
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Hello eoren1

You only have a couple of options on how to change your ungrounded 2 prong outlets to 3 prong outlets.

Here is a drawing on some of the ways the electrician can wire up your new 3 prong outles.

Hope this helps-----Let us know how you made out with your project.

Have A Nice Day

    Bookmark   January 8, 2010 at 11:15AM
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Got a question for you, Linesman. What are those green wires linking the ground posts of the outlets?

It seems to me that adding them when there is no actual method of grounding just aggravates the situation since, in the future, someone may incorrectly conclude that there is a proper equipment ground present.

Yeah, I know that there is supposed to be a label indicating "no equipment ground", but those are often washed off or peeled off or they disappear when somebody changes covers.

I dunno. This seems like a "truth-in-advertising" issue to me that's likely to do more harm than good.

    Bookmark   January 8, 2010 at 12:04PM
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The ground conductor from the GFCI receptacle to the other 3-prong receptacles serves no purpose, and is not required.

    Bookmark   January 8, 2010 at 12:51PM
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The ground conductor from the GFCI receptacle to the other 3-prong receptacles serves no purpose, and is not required.

Actually, the conductor is specifically prohibited by 406.3(D)(2&3). Should the GFCI fail, an uncleared ground fault at one receptacle would be shared by receptacles connected by ground wires.

Linesman's drawings C & D are wrong.

    Bookmark   January 8, 2010 at 7:41PM
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Thanks again for all of the comments.
We close on Friday and, at that point, I'll have free reign. I have noticed three prong outlets in the basement which leads me to hope that the outlets are groundable but that they just put in the 2 prongs. Is there an easy way for me to tell when taking the outlet covers off if the outlets are groundable?
Thanks again,

    Bookmark   January 9, 2010 at 2:16PM
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If they are truly ground-able, it means that, when you SHUT OFF THE BREAKER FOR THE BOX and pull out the receptacle, you will find a black and white wire connected to the receptacle and a bare copper wire coming out of the Romex cable that is not presently connected to anything; this would be your possible grounding wire. To meet code, this wire: 1) needs to be long enough (6" outside the box), and 2) be grounded all the way back to the breaker box, which means that all the ground wires on all the circuits must connected up so that you have a continuous run to the breaker box. If this wire is not present (as I suspect you will find), or if it can not be connected up to the breaker box, then you can't ground the receptacle without the electrician pulling a new ground wire or a new Romex cable to each box. If you can't do that, then installing GFCIs is your only alternative to improve safety.

    Bookmark   January 9, 2010 at 3:29PM
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Thank you Kudzu9
I'll report back when I hear from the electrician and/or check it out myself next week

    Bookmark   January 9, 2010 at 7:18PM
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Good luck. I'll be interested to hear what you have to report.

    Bookmark   January 10, 2010 at 4:22PM
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A fundamental question....why are you bothering to change every outlet merely because it is a 2 prong? I faced the same scenario but realized that practically no lamps, clocks, or other appliances I own even had 3 prong plugs on them to begin with. Naturally, in areas such as the laundry and kitchen it was a must because the refrigerator, stove, dishwasher all had plugs which required 3 prong outlets.

    Bookmark   January 14, 2010 at 11:24PM
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The house is ours!!!
Below are pix of the opened outlets. Please tell me that red wire is a ground...
As for the question or why to change them, got two little kids so, at a minimum I'm going to change them to tamper resistent and figured I would just get three prong ones for their room. Ours will have TV and possible computer so will need at least one 3 prong. You do raise a very good point though.
On with the pix:

    Bookmark   January 15, 2010 at 3:29PM
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You also need some box extensions to get the front face of the box within 1/8 inch of the face of the wall.

the red wire attached to the receptacle is probably a hot, possibly switched.

You need to measure form the hot to the metal box itself.
If you get a good solid 120 V (or whatever is from hot to neutral on the receptacle) you might have a ground present.

I cannot see the back of the box well enough to tell if AC cable is present, but the wire insulation (likely cloth over rubber) was used in a lot of AC cable.

NM (plastic sheathed cable) came in later so the clothe is rarely present.

Some careful cutting of the wall should allow you to see the cables entering the box (and still be covered by the plate) if you cannot see them inside the box.

Keep in mind that while GFCI devices can protect people when a ground is not present, surge devices to protect your computer really need a ground to function correctly.

It would be worth the trouble to get a very good ground for any electronics.

    Bookmark   January 15, 2010 at 4:07PM
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Thanks for the post. Sorry but I lost you somewhere around 'box extensions' :)
I'm planning on putting in a central surge protector off the new 200A service regardless.

    Bookmark   January 15, 2010 at 4:56PM
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Congratulations on your new home!
The red wire is not a ground.. This outlet appears by your pictures to be controlled by a wall switch since I see two black hot wires which are wire nutted together in the back of the box. If so, the red is a switch leg.
Here is how you can solve your grounding question....go down to the basement and examine the cables which are entering your fuse or circuit breaker panel. If they are BX (metal spirals) then your metal boxes should be grounded. Get a light tester and touch one end to the metal box in the wall and the other end to the black (or red) terminal (make sure the wall swich is on, if applicable)...if the light goes on, you have a grounded system and you can install the 3 prong outlets and they will provide ground in the 3rd slot. Please note that if you have BX, you will not have a green wire to attach to the green screw on the new outlet, nor will you need one since the screws will make contact with the ground of the metal box automatically.
Just a word of advice. If you truly do not need a grounded outlet, it is sometimes better to leave the old ones alone. Cloth covered wires are usually fine when left undisturbed, but when you pull them out and push them back the insulation can fall off and leave you with a bigger problem than you started with. Good luck and enjoy your new house.

    Bookmark   January 15, 2010 at 5:08PM
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Thanks Scottys. That was very informative.
Now let me ask a very stupid question - do I need a grounded outlet? We're only talking about the 4 bedrooms on the second floor. One for each kid (2 and 4 years old), a master and a guest room. Kids will have lamps and clock radios, humidifier; fish tank for the boy. We will have an LCD HDTV, cable box, possible media extendor/miniPC to stream movies from below. I was already planning on a bit of work to the master to put in Cat5e cable. Figure it would be little extra work/money to put in three prong grounded outlets given the increased demand in that room. As for the kids and the guest room, are there any reasons to mess with the outlets/wires? Is there any added safety considering the kids young ages? Would it be reasonable instead to put in a tamper resistant outlet?
Here's one

I can't find any that are only two prong.
Alternative would be this one that is GFCI

Thanks again,

    Bookmark   January 15, 2010 at 5:19PM
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Electrician has been to the house and notes that all outlets are grounded. Will keep three bedrooms as-is with two prongs. Master will get changed out to 3 prongs for future HDTV, etc.
Thanks for all the comments and help!

    Bookmark   February 6, 2010 at 11:06PM
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