Switching 2 prong to 3 prong outlet

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  #1  
Old 07-24-03, 10:57 AM
bikeboy
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Question Switching 2 prong to 3 prong outlet

I recently purchased a house built in 1940 (if you need that info). It has the older two prong outlet thoughout the house. I switched over some of them to three prong outlets. I wired them correctly hot/hot and neutral/neutral. Using my tester its telling me that the outlets are grounded. I have been reading and not getting a clear picture if I need to do anything else for the ground. I read somewhere that I need to attach a ground wire to the green screw on the new 3 prong outlet and then where do I attach that screw??? If that is indeed what I need to do. The question is what do I need to do if anything and why? I want to be safe. I occationally when I plug something in see a very small spark. This doesn't happen everytime, just occationally.

Thanks in advance
Mark
 
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  #2  
Old 07-24-03, 01:09 PM
Gary Tait
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Do the new recepticls have a spring clip arount the screw at the one end?
If not, you need to run a ground wire between the receptacle and the box.
 
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Old 07-25-03, 11:50 AM
bikeboy
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I'm not sure if it has a spring clip, nor am I 100% sure I know what that is. It seems pretty self-explanitory. I'll check that when I get home today. If it doesn't, how do I run a ground wire from the outlet to the box. I know I need to run it from the green screw on the outlet but how do I run it to the box, where should I attach it. Also what do I use for my ground wire? Should I just by some 14/3 wire at the store and just cut out a piece of the bare copper/ground that is in there or can I get something else?
Thanks again
Mark
 
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Old 07-25-03, 04:59 PM
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This is a bit more complex than you might at first think. You may be reading a ground thru some flexable metal conduit which doesnt make a good ground. It the wire in flex or like Romex cable, or is it conduit?
 
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Old 07-25-03, 09:51 PM
bikeboy
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It is flexible metal conduit. What to do then to get a "good" ground?
Thanks
Mark
 
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Old 07-26-03, 08:19 AM
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Replacing 2-prong receptacles with 3-prong Grounding receptacles where the existing Wiring Method is "old" Armored Cable is practicaly SOP with most electrical contractors.

ANY Ground is better than NO Ground, and Grounding-type receptacles are effective ONLY when a 3-prong cord-cap is inserted in the receptacle, presuming the Green wire in the cord is bonded to the metal of the connected load.

If you have Grounding-type receptacles on the kitchen counter-top and plug in an appliance equipped with a 2-wire cord, you still have a serious shock-hazard because the metallic surface of the appliance is not Grounded.This is the reason the Code requires GFI protection for receptacles in that specific location ,in addition to other locations the house.
 
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Old 07-26-03, 09:06 PM
bikeboy
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PATTBAA,
What??? What does this mean in human terms please "practicaly SOP with most electrical contractors"
I am not really understanding your post.
Please explain
Thanks
 
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Old 07-26-03, 09:35 PM
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it is a NEC (National Electric Code) violation to replace the two prong receptacle with a three prong grounding version without an approved ground. Armored cable sheath is not an approved grounding conductor. The only legal and safe way to do this is to replace the receptacles with GFCI (Ground Fault Circuit Interrupters) receptacles. You must then affix the sticker that says "No Ground Connected" (comes with the GFCI) to the wall plate to alert people that the receptale is not grounded even though it has the third grounding prong. I do not know of any electrical contractor whose SOP (Standard Operating Procedure) is to violate the NEC and open themselves up to liability when someone dies from shock or fire. Also, if you make the changes you previously stated and something happens, your insurance company may not pay!
 
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Old 07-29-03, 09:19 AM
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The relevant Code article on the issue of using the metallic sheath of Armored cable as an Equiptment Grounding Conductor (EGC) is Art. 320.108 , Equiptment Grounding,which reads-----"Type AC cable shall provide an adequate path for Equiptment Grounding as required by 250.4----). (2002 NEC)

That is ALL that is stated in the Article. The Article DOES NOT state----" shall provide and adequate path AND SHALL CONFORM TO THE REQUIRMENT of Art 320.100" (which requires a bonding strip. To posit that Article 320.108 specifically prohibits the use of Armored Cable without the bonding strip as an EGC is to add words and restrictions to the Article that are not stated in the Article.

At some "point in time' the NEC added the requirement of 320.100. If it is presumed that the "new" Armored Cable automaticaly became the ONLY Type of Cable that could serve as an EGC,then it must be presumed that all existing installations with the "old" Armored Cable automaticaly became de-facto Code violations because NOTHING ( boxes, motors, fixtures) could be considered properly Grounded.

I now quote statements culled from two un-impeachable sources on the issue of the bonding-strip. The first is from the "NEC Handbook", 1996 edition.

"The ARMOR of Type AC cable is recognized as an EGC. (the internal bonding-strip) increases the ARMOR's effectivness as an EGC"-------Please not the implication----the cable ARMOR is the "primary" EGC, not the bonding-strip.

More specific in this statement from "Electrical Grounding", auth Ronald Riley, based on the 1996 NEC.

"The metal bonding-strip in Armored Cable is neither designed or put there with the intent that it be used as an EGC. The primary prurpose of the strip is to maintain continuity across any opening that might result from bending the Armor. The outer flexible Armor ALONE is depended on ----- to conduct any Fault-Current and to have aqequate low-impedance"
 
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Old 07-29-03, 05:27 PM
Kray
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I have a few questions related to this same topic so thought I would piggy-back on here. When built in 1963, my house was wired with 14-3 copper wiring but all original receptacles were the old two-prong variety. My questions:
1. I thought the two prong receptacles were used in the older "2 wire" systems. Since my house was wired with 14-3, I've been curious why the builder did not use 3-prong outlets? Just saving a few pennies, maybe?
2. I've been gradually converting the 2-prong outlets to 3-prong
outlets. For each 3-prong receptacle I am running a short piece of bare (or green) wire from the screw at the back of the metal outlet box to the green screw on the receptacle. Is this the way to do it? Any other requirements to keep in mind in making this conversion?
3. I'm a little confused by the fact that some of the boxes, added during remodeling projects, are plastic instead of metal. Obviously, they have no grounding screw in the back. In this case. what should be done with the green grounding screw on the 3-prong receptacle? I've been assuming it should be connected directly to the incoming ground wire, or via a pigtail if there is a ground wire both entering and exiting the box? Is this correct?
4. Finally, from viewpoint of grounding and safety, which type of outlet box is best, metal or plastic? Or does it matter?
Thanks
 
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Old 07-30-03, 08:07 AM
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To the best of my knowledge, 2-prong receptacles were permissible in 1963.The transistion from 2-prong to 3-prong was gradual. The first Code requirement for Grounding receptacles was not applied to all receptacle outlets.When it was decided to require all receptacles to be the Grounding-type, a time-period was allowed for factories and supply-houses to dispose of their stock of 2-prong receptacles.

You were astute by connecting a jumper between the receptacle and the metal outlet box. Non-metallic cable has the most effective Equiptment Grounding Conductor for receptacle circuits because the bare EGC is the same size and the same metal ( copper) as the Neutral (White wire) Branch-Circuit conductor. A superior Wiring Method for a"custom" residential installation would be Armored Cable equipped with an insulated Green EGC.

An advantage to plastic outlet-boxes is the cubic-inch volume of the boxes.
 
  #12  
Old 07-30-03, 11:57 AM
DaveB.inVa
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Originally posted by PATTBAA
[More specific in this statement from "Electrical Grounding", auth Ronald Riley, based on the 1996 NEC.

[/B]
Thats a great book as far as installation practices and code references... but I have a large problem with the "Electron Creed" where it says "Do you believe electrons are always trying to get back to earth"... then it says "I do" after that statement.
 
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