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Adding a three prong plug  Rate Topic 
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 Posted: Sat Nov 2nd, 2019 06:13 pm
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Alan Jurisich
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So I'm ordering supplies to finish up my vortalex and some electrical safety popped into mind concerning the metal chassis.  Obviously there's some risk of electrical shock through the chassis if I did a poor job of insulating my union/splice points and they were to contact the chassis.  So I'm considering installing a three wire power cord to add a chassis ground as a safety measure.  I went to looking for a 1950's styled three pronged plug and have been surprisingly disappointed.
So it got my wondering how often someone has had issues with electrical shock from a chassis.  How many people have done a fairly reasonable wiring job and had a shock hazard develop over the course of operation?  Am i perhaps being overly protective. Now in my work there's technically no such thing as over protective until you have someone wearing insulating gloves and gauntlets to work on 120 or wearing a heavy Cal suit to work on de-energized (and locked out tagged out / pulled out of service) 4160 equipment.  At that point you're just impeding your ability to work effectively/safely. That was pretty off topic there but main question is:

Is anyone in the forum of the opinion that adding a chassis ground to your vintage fan is a worth while safety investment even if your being very mindful of insulating your electrical junctions? If so, where do you find your plugs at?

My brain is telling me yes, and if i can't find a period appropriate styled plug to fit that I'll do the best I can to at least make it appeasing.

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 Posted: Sat Nov 2nd, 2019 09:34 pm
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Stan Adams
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The safest thing to do is run it through a GFCI receptacle, then you don’t have to worry. Your 50s model should not leak, so probably would not have any issues with a three prong cord. Many of the really old fans leak & have some real issues with a 3 prong. Also make sure your cord is polarized with hot or small prong going to the switch.

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 Posted: Sat Nov 2nd, 2019 11:20 pm
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Alan Jurisich
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I assume by leak you mean lubricant. So what kind of issues did this cause? Is it not sensitive enough to trip from the creepage to the chassis caused by the lubricant? Or is it the lack of protection from a hot to neutral short?

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 Posted: Sun Nov 3rd, 2019 12:08 am
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Stan Adams
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By leakage, I mean current leakage. Many older induction motors have a certain amount of leakage from inductive currents. Some/most if not polarized will leak through the old insulation. If you get an electrical tester which beeps, if you plug it in one way with the switch being on the neutral leg, the hole fan will beep with voltage. If you flip the plug around, everything is fine.

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 Posted: Sun Nov 3rd, 2019 04:15 am
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Patrick Ray
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I make some antique-style extension cords and some I make are grounded.  Grand Brass makes antique-style grounded plugs and are really nice quality. They have these in black, brown, white.
https://www.grandbrass.com/item/plgb04bl/plugs-nema_5_15p_grounded_plugs/

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 Posted: Sun Nov 3rd, 2019 05:15 am
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Nathan Britt
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I like to put a polarized plug on and wire the hot wire to the switch. This will cut the windings out of the circuit when the fan is off. If you're still worried, a GFCI will trip if it detects a substantial leakage. If I'm not mistaken Snake Head Vintage sells a polarized bakelite half round plug that is period correct.

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 Posted: Tue Nov 5th, 2019 09:04 pm
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Jim Kovar
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Nathan Britt wrote: ...a GFCI will trip if it detects a substantial leakage.
Substantial?  :wondering:

A 5 milliamp ground fault...
...circuit break within
          as little as 1/40th of a second...

Chances are you won't even feel it. :thumbup


Last edited on Tue Nov 5th, 2019 09:09 pm by Jim Kovar

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 Posted: Tue Nov 5th, 2019 10:33 pm
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Steve Sherwood
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I believe the "leaks" are referred to as Eddy Current.

https://www.youtube.com/watch?v=BIsKthqeKSo

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 Posted: Wed Nov 6th, 2019 03:01 pm
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John McComas
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Steve Sherwood wrote: I believe the "leaks" are referred to as Eddy Current.

Sorry Steve, no cigar. 

Eddy currents are generated in moving magnetic fields that are generated by alternating currents in ferrous materials. 
(That's why we have laminated stators in AC motors.)  Eddy currents are like short circuits within
the stator core and create wasted energy as heat.  DC motors with solid iron cores do not
have eddy current problems, but if you ran AC in a solid metal stator, you would have Eddy current problems.
Laminated stator plates can be used for both AC or DC motors.


Electrical leaks are generally caused by breakdown in the insulation between the power wiring and the motor case.
They can be AC or DC.  The amount of leakage is defined usually as milliamps of leakage current.

I can't believe you didn't offer to give me a ride in your pimp mobile! :cry:

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 Posted: Sat Nov 9th, 2019 08:28 pm
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Steve Sherwood
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I will bring it to Pig Pickin. I will pick you up.

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