need polarization safety help...

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  #1  
Old 08-15-02, 02:39 PM
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JeffNelson
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need polarization safety help...

My problem is I have many old lamps without polarized plugs. So I am trying to figure out what is the safest and NEC legal way to have them plugged in. Logic tells me the hot wire should goto the middle tab in the lamp socket. That way if it was plugged in and no bulb in the lamp someone would have to reach in and touch middle tab to get a shock instead of hitting the threads. But here is where I am confused. I have a UL listed nightlight for the bath room so I tested it thinking I could get the right answer from that. However it has the hot side wired to the threads so I am really confused. I was hoping someone could tell me the correct way to have old two conductor nonpolarized lamp plugs to be plugged in.
-Jeff
 
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Old 08-15-02, 03:52 PM
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We had this disscussion earlier and I was corrected,,, there is a code that says the it is supposed to be hot in the middle. It seems that I have seen them the other way also somewhere but Mr. Goodrich and sparks set me straight.
 
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Old 08-15-02, 04:36 PM
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bwetzel
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Does this two prong plug have one side bigger than the other. Some do not, so you could plug it in different everytime.
 
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Old 08-15-02, 04:52 PM
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Polarization

The ridged side of the lampcord is the identified conductor wich is used as the grounded conductor of the circuit. The grounded conductor should be connected to the wider blade of a polarized plug and to the screw shell of the lampholder. The other conductor of the lamp cord should be conected to the smaller blade of the polarized plug and to the switch. The other contact of the switch should be connected to the center contact of the lampholder.
--
Tom
 
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Old 08-15-02, 09:00 PM
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JeffNelson
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sberry27-
Thank you that is exactly what I was thinking.

bwetzel-
As you have probably figured out by now I was speaking of a two conductor cable and plug that did not have one blade of the plug enlarged to force the right polarization. I know it can be plugged in either way but I want to replace this nonpolarized plug with one that is for safety sake and was looking the answer if there was a code on it. sberry pointed(thank you)that there is and I had the right idea the first time. Thank you for your time in assitance though.

hornetd(Tom)-
Have no idea what you said because it is way over my head but thank you for taking the time to respond.

-Jeff
 
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Old 08-16-02, 05:16 AM
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hornetd's answer is precisely the information you are looking for. I would suggest you take the time to understand it. The important points are:

(1) Modern lampcord (i.e., the wire used for making cords for lamps) is polarized. If you look closely you will see that the insulation on one side of the cord has ridges in it, the other side is smooth. The side that is smooth is hot, the side with ridges is neutral. (This is mainly of interest if you are changing the cord for a lamp as well as the plug, as your older cords are probably not ploarized.)

(2) Plugs are also polarized (as you know), the narrow blade being hot and the wider blade being neutral.

(3) The lamp switch should be connected to hot. You always switch hot, you never switch neutral.

(4) The screw shell (threads) of the lampholder should be connected directly to the neutral. The center contact connects to hot through the switch.
 
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Old 08-16-02, 11:12 AM
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mikewu99-
How is what you just said any different then what sberry said but in simplier terms? First the two conductor old lamp cord has no such difference. It appears to be around a 14guage brown lamp cord. I knew how to find which wire does to the threads and which goes to the tab. I just used a multimeter and used the continuity tester. I was just trying to find out if there was a code for which polarization was to go. Logic told me from a safety stand point it would be in the inner tab and the nuetral would be threads. sberry gave me exactly what I was looking for there is a code and you always wire hot to the inner socket tab. Problem solved I put a new plug on the old lamp which is a polarized plug so it can only go in one way. Thanx for explaining it just turned out to be more info then I needed.

-Jeff
 
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Old 08-17-02, 05:16 AM
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Originally posted by JeffNelson
mikewu99-
How is what you just said any different then what sberry said but in simplier terms? First the two conductor old lamp cord has no such difference. It appears to be around a 14guage brown lamp cord. I knew how to find which wire does to the threads and which goes to the tab. I just used a multimeter and used the continuity tester. I was just trying to find out if there was a code for which polarization was to go. Logic told me from a safety stand point it would be in the inner tab and the nuetral would be threads. sberry gave me exactly what I was looking for there is a code and you always wire hot to the inner socket tab. Problem solved I put a new plug on the old lamp which is a polarized plug so it can only go in one way. Thanx for explaining it just turned out to be more info then I needed.
-Jeff
I missed the fact that you were looking for a code citation. Here is the applicable section of the 2002 NEC .

410.23 Polarization of Luminaires (Fixtures).
Luminaires (fixtures) shall be wired so that the screw shells of lampholders are connected to the same luminaire (fixture) or circuit conductor or terminal. The grounded conductor, where connected to a screw-shell lampholder, shall be connected to the screw shell.



--
Tom
 
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Old 08-19-02, 04:54 AM
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JeffNelson:

If you think I gave you too much information, I apologize. You indicated that you did not understand hornetd's reply and I was just trying to clarify it.

IMHO there is no such thing as too much information.
 
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