Weird line cord


I installed my window air conditioner and the GFCI on the end of the cord would not reset. I figured I would replace the plug and get an inline GFCI to replace what was there.
I cut the plug off the end of the cord. As I was doing this I was wondering how I would figure out which side was black and which was white. Well I looked at the cut end and to my relief I saw a white, black and a green conductor inside the sheath, OK a piece of cake.
As I cut back the sheath I found that the white and black wires were wrapped with a copper shield like the outer conductor in CATV cable.
I was like what was I supposed to do with this shield. I cut it back the "shield" to keep it away from the terminals, put the plug together plugged into the GFCI and every thing worked.
So why the "shielding"?
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Cliff Hartle wrote:

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That's what I would think but what about an air conditioner needs shielding?

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Cliff Hartle wrote:

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*Are you sure that was a GFCI on the end and not an AFCI?
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http://www.peterspirito.com/afci_faq.htm What are the National Electrical Code requirements for AFCI's?
AFCI's were added to the 1999 National Electrical Code in Section 210-12 for bedroom receptacle outlets beginning on January 1, 2002.
The 2002 NEC (Section 210.12) requires AFCI's for all bedroom circuit outlets. An outlet is defined as any point on the wiring system at which current is taken to supply utilization equipment. This includes receptacles, lighting fixtures, ceiling fans, smoke alarms, etc.
The 2005 NEC (Section 210.12) has the same requirements for bedroom circuit outlets with one exception - the wording changes to specifically require a Combination Type AFCI beginning January 1, 2008. In all cases the requirement is to protect the entire branch circuit.
NEC Article 100 Definitions
.Branch Circuit - The current conductors between the final overcurrent device protecting the circuit and the outlet(s). .Outlet - A point on the wiring system at which current is taken to supply utilization equipment. Please see the NEC for the exact wording of the requirements. Some areas may adopt other effective dates and may expand the requirements beyond the bedroom circuits. Contact your local authority having jurisdiction (AHJ) to verify code requirements for your area.
Why do the 1999, 2002, and 2005 versions of the NEC require AFCI protection for only bedroom circuits?
NFPA fire statistics show that a high percentage of electrical fires occur in bedrooms. There are many appliance cords in bedrooms, for example, radios, clocks, blankets, air conditioners, heaters, TVs, vacuums, as well as, lamp cords. All of these cords can be trapped/abused leading to arcing faults. Further, there are long runs of installed wiring (M-B, "Romex") between the loadcenter and the bedroom outlets. The wiring can be abused during installation (e.g. stapling) and after installation (driving nails into the wall etc.) Therefore, the most logical room to start with would be the bedroom.
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Also, people sllep in bedrooms and maynot awake in time.
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the braid is likely to protect other devices in room for RF spikes off the air conditioner
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*Article 440.65 of the 2008 NEC requires a leakage detector or an AFCI on corded room air conditioners..
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Cliff Hartle wrote:

Did you test the outlet before chopping the cord off?
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I question why you would want or need a gfi on a window unit.
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Who knows what goes on in the mind that writes the codes. I would guess that if it is a window unit, someone could be outside on the ground and if there was a short of the hot wire to the case of the AC then if touched you could get shocked.
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Ralph Mowery wrote:

Ya know what? That's exactly true. I recall some years back a woman who had been swimming was electrocuted as she tried to enter her hotel room. At first they kept mentioning that it had an electronic card reader type lock, but further investigation found a short from the A/C unit below the front window to the steel door frame.
I also have a window unit with a built in GFCI on the cord.
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I didn't check to see if it really was a GFCI I just assumed it was.
As for why its needed, my thought is its an appliance that half sits inside, half outside and the base is full of water.
You know the whole water and electricity don't mix.

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That makes perfect sense. It is really an outdoor appliance and so ought to be gfi protected. Maybe I'll put a plug-in gfi on my window unit. That'll be this weekend's trip to the big-box.
I would also guess (no stronger word) that the shield is for RF and is not an electrical-safety component. See if you can expose the shield in the remnants of the cut-off plug, and use an ohmmeter to see if it's connected to the ground pin. If so, you can maybe connect it to the ground in the replacement plug too.
But if it's also connected to the grounded chassis of the a/c unit, that's probably all that's needed. In shielded communications cables (ie, old rs-232 cables), the shields were *not* to be connected at both ends, to prevent ground loop currents between equipment with different earth potentials (common in large buildings). I can't see that that could arise here. But the point is that the shield only needs one ground connection point to be effective.
Now, why would the old gfi plug not reset? Maybe the unit has developed an internal short? On the old plug that you cut off, if you can safely insulate all the conductors that are coming out of it, try plugging it in and seeing if it will reset now. If so, that a/c unit probably has a real problem.
Chip C Toronto
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On 5/29/2010 6:39 PM, Cliff Hartle wrote:

Back in the early 1970's I worked for an electrical supplier when ground fault breakers first became widely available. One of the problems with the new fangled devices was RF sensitivity, the breakers would trip every time someone keyed the transmitter on a ham or CB radio. It's quite possible that the shielding is to prevent spurious tripping of the built in ground fault for the AC unit. It may be that it is so sensitive to RF from things like cordless phones or cellphones that the shielding proved to be a necessity.
TDD
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wrote:

I think the device is supposed to shut off power if the cord is damaged. Like if your dog bites into the cord, connecting one of the conductors to that "shield" through conductive canine saliva.
--
Mark Lloyd
http://notstupid.us
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On Sun, 06 Jun 2010 19:21:05 -0500, Mark Lloyd

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On 6/6/2010 7:21 PM, Mark Lloyd wrote:

My sister and husband had a weird dog that would get mad and run about the house pulling electrical cords from the wall sockets. One time the goofy canine bit in to a live one and after a long session of yelping, decided not to ever do that again.
TDD
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