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Polarity on SPT Homemade Ext. Cords


jim6918

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Now I am really showing my ignorance of basic electricity. Earlier this week, when I started cutting and making up my SPT runs, I was very careful to pay attention to the ribbed side of the wire so that I could line it up with the neutral side of the male plug. I "assumed" that the neutral side of the female plug was the same way, however my buddy who was helping me yesterday noticed that it is opposite on the female plugs. So that means I have about a dozen or so extension cords wired incorrectly. I have always noticed that most (if not all) incadescent mini light sets do not have a polarized male plug so to me that would indicate that polarity is not an issue. New to me this year are LED stringer sets cut to custom lengths. I have 11 of these LED strings wired incorrectly, but the kicker is that every one of them light correctly.

Should I climb up on the roof and change these plugs around, or does it really make ia difference?

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It doesn't make a difference with Christmas lights... BUT *I* would make them right. You never know what you may use these cords for in the future and it's just piece of mind knowing they are correct.

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Jeffrey wrote:

It doesn't make a difference with Christmas lights... BUT *I* would make them right.  You never know what you may use these cords for in the future and it's just piece of mind knowing they are correct.


It does make a difference in safety, namely with C7 or C9's. I know you didn't mention them, but reversing the polarity on those will result in the side of the bulb being hot instead of the base tip area. Much easier to get shocked that way.

But not a big deal on mini's...
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Jeremy Wiles wrote:

Jeffrey wrote:
It doesn't make a difference with Christmas lights... BUT *I* would make them right. You never know what you may use these cords for in the future and it's just piece of mind knowing they are correct.


It does make a difference in safety, namely with C7 or C9's. I know you didn't mention them, but reversing the polarity on those will result in the side of the bulb being hot instead of the base tip area. Much easier to get shocked that way.

But not a big deal on mini's...

I did a little Googling after I posted this and in one fairly interested article did notice that there is a shock concern because one side is hot all the time.
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Not sure what you mean about the "female side being opposite". With SPT wire, the smooth, printed (usually embossed) side is the hot, and the ribbed side is the neutral. This should be true for both male and female ends, unless the cord was improperly manufactured...

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I'm not sure what you mean by "opposite on the female plugs" either. Your mini's and Led's will work with the polarity reversed but for safety I would correct the cords. You never know, next year that cord might end up on somepart of the display where polarity does matter.

Darryl

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Let me try to explain. If you look at a male alligator plug, the neutral prong that pierces the insulation is nearer the front of the slot where you first insert the wire and then bend over. On the female the neutral prong is at the rear of the slot, so you have to flip that end of the wire over to maintain polarity. If you have male and female alligator plugs, look at them. I am probably not doing a very good job of 'splaing.

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I know exactly what you mean. I noticed the same thing. If you think about it though, when you put the female on one end, connect the wire and if you left the wire in a straight line when you get to the other end, you have to "turn" the male around to go on the other end. So keeping the wire oriented the same way in that example puts the teeth in the same orientation...

Probably makes even less sense with my $.02, but I did notice the same thing...

J.

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Jeremy Wiles wrote:

I know exactly what you mean. I noticed the same thing. If you think about it though, when you put the female on one end, connect the wire and if you left the wire in a straight line when you get to the other end, you have to "turn" the male around to go on the other end. So keeping the wire oriented the same way in that example puts the teeth in the same orientation...

Probably makes even less sense with my $.02, but I did notice the same thing...

J.

Thank God. I am glad I wasn't losing my mind. The way you described it makes more sense than my description.
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I'm with you now!

I'd fix the cords. If you ever use a wiring harness that has a shared neutral, that depends on having properly polarized plugs (if not you can blow triacs/fuses due to the dead short that results)

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One more day of nice weather, so I guess I"ll haul my sorry butt on weak knees up on the roof and change the plugs. Thanks for all the replies.

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Also, different batches of plugs may have different orientation for which way the ribs go relative to how you hold it. This year, all the ones we have appear to work correctly if held the same way. Other years I have had to tell people to always figure out which blade is the wide one, and where its prong is, to line up the ribbed side.

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When I made mine I ignored the ribbed and smooth (to tell the truth I didn't notice the difference) but the large prong (male) lines up with the large slot (female). I used a multimeter to test them.

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PaulXmas wrote:

When I made mine I ignored the ribbed and smooth (to tell the truth I didn't notice the difference) but the large prong (male) lines up with the large slot (female). I used a multimeter to test them.


At least they are fine for now. The reason that convention could still be important is if you go back and convert some of those into two shorter cords in a couple years. Will you, or someone helping you work on your display remember that you had some that were not conventional?

Separately, on the importance of polarization and C7/9 strings. LOR does it right, and switches the hot lead, but some other products do exist that switch the neutral, so that even with the bulbs off, either the hot or neutral lead may get you.

With LOR, if the string is live, and the thread is hot instead of neutral, someone could get zapped by the thread while unscrewing a bulb, even after the bulb turns off, as long as the thread is still in contact. If hot is on the center contact, once it breaks contact, the bulb goes off, and the thread stays neutral, and unable to shock you by itself.
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-klb- wrote:

PaulXmas wrote:
When I made mine I ignored the ribbed and smooth (to tell the truth I didn't notice the difference) but the large prong (male) lines up with the large slot (female). I used a multimeter to test them.


At least they are fine for now. The reason that convention could still be important is if you go back and convert some of those into two shorter cords in a couple years. Will you, or someone helping you work on your display remember that you had some that were not conventional?

Separately, on the importance of polarization and C7/9 strings. LOR does it right, and switches the hot lead, but some other products do exist that switch the neutral, so that even with the bulbs off, either the hot or neutral lead may get you.

With LOR, if the string is live, and the thread is hot instead of neutral, someone could get zapped by the thread while unscrewing a bulb, even after the bulb turns off, as long as the thread is still in contact. If hot is on the center contact, once it breaks contact, the bulb goes off, and the thread stays neutral, and unable to shock you by itself.

After getting zapped a few times I have a very healthy respect for electricity! "IF" I shorten the cords I will make sure they are correct!

When I wired up my relay I checked and double check that everything was correct before I took it outside in the yard well away from everything plug it into an extention cord that I plugged into a power bar that was switched off....took a deep breath and hit the switch!

No smoke or fire this time LOL

I checked the ground and polarity with a little yellow tester on everything I wire up.
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