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Re: Replacement receptacles [Re: renosteinke] #184200 02/04/09 01:28 AM
Joined: Jan 2004
Posts: 1,507
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George Little Offline
Member
Okay gang- I was baiting you as is the habit with me.
Reno has covered part of it in that the plate would not be grounded and even if one were to use a non-metallic plate and nylon screws the yoke would not be grounded. There is an exception for a work around it in 406.2(D) so that's covered but the contractor would not be permitted to use the uninsulated conductor of the 12/2 w ground on the "Isolated Ground" terminal per 250.146(D)

What really gripes me tho is that the contractor had sold him a bill of goods on how much better system this was and I couldn't say anything to anyone but the contractor about his unprofessional deed.

Last edited by George Little; 02/04/09 01:34 AM.

George Little
2017 / 2014 NEC & Related Books and Study Guides
Re: Replacement receptacles [Re: George Little] #184201 02/04/09 02:02 AM
Joined: Aug 2007
Posts: 853
L
leland Offline
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Baiting is good!

If this one is so sly,would they not have grounded the yoke with the same conductor?

Re: Replacement receptacles [Re: leland] #184203 02/04/09 02:42 AM
Joined: Sep 2005
Posts: 99
T
Tripp Offline OP
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You guys are killin me. This is better than a Hitchcock movie. So don't quit me now!

- Tripp

Re: Replacement receptacles [Re: gfretwell] #184206 02/04/09 10:08 AM
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SteveFehr Offline
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Originally Posted by gfretwell
Actually I imagine the trip through the little toroid transformer might filter out some small transients. I know an engineer who said a simple overhand knot in the cord would filter out some very high frequency noise. I don't know how true it is but I am never in a hurry to untie a knot that develops in the cord of my electronics.
Tying an overhand knot or putting a loop in a piece of wire increases the inductance and can, indeed, attenuate high-frequency noise and dampen some transients. Wrapping the cord around a ferrite choke will be more effective since the pereability of iron is so much higher than air, but just a loop in air will help, too.

A single loop has negligible impedance vs 60Hz, but don't go overboard or you could end up with a DIY power factor "correction" inductor and increase circulating current in your circuit.

Re: Replacement receptacles [Re: renosteinke] #184300 02/06/09 06:48 PM
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BrianP Offline
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Originally Posted by renosteinke
I do see the need for a real ground path, though. Electronic appliances often use the ground path ... either to always have power ("instant on," timers, motion sensors, etc.), or in order for the surge suppressor to work.


Any intentional use of power should never use the ground path. The grounding conductor is used for grounding of any metal parts (safety ground) and surge suppression.

Most surge suppressors have 3 separate surge suppression devices in them. One protects against line-to-neutral (L-N) surges, one protects against line-to-ground (L-G) surges, and one protects against neutral-to-ground (N-G) surges. Without the ground, the L-N protection should still work, but the L-G and N-G will not.

Re: Replacement receptacles [Re: BrianP] #184304 02/06/09 08:14 PM
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Posts: 5,316
renosteinke Offline
Cat Servant
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"Should" is a fine concept, yet it is a fact that the ground path is utilized by a variety of products as a conductor for minor amounts of power.

This is, perhaps, why the NEC only bans "objectionable" current on the ground.

I've lost count of the sundry light fixtures and replacement ballasts that come with the caution "will not work without a good ground" marked right on them.

Re: Replacement receptacles [Re: renosteinke] #184305 02/06/09 08:25 PM
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BrianP Offline
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I know that some ballasts rely on the grounded metal close to the lamp for starting. Your original statement was about electronic equipment, not lamp ballasts. There is no reason a computer, TV, stereo, etc. should use the ground for power. Modern electronics all run on low DC voltages (12V, 5V, 3V, etc.), and these DC voltages are produced by a power supply. The power supply only needs the line and neutral. The ground is there only for safety.

Again, fluorescent lamps (and perhaps other ballasted lamps) are a special case, and some of those do need a ground for proper operation. Computers, stereos, etc. do not. (An earth ground may have an impact on system noise on a stereo.)

Re: Replacement receptacles [Re: BrianP] #184312 02/06/09 10:44 PM
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renosteinke Offline
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Wee, I'm not about to get into word play; nor is it my ambition to dissect everthing I encounter.

The ballasts with such lables have all also touted themselves as "electronic." Whatever is inside the mysterious black box, they seem to have left out the heavy, gooey, tar.

Likewise, we have documented, on this very site, other electronic devices that most definitely had current to ground in normal operation. Motion sensors, photocells, and even SOME illuminated switches utilize the ground as a conductor.

I can also point to the 'wall switch' type intermatic timers as something that includes the 'we need a ground' statement.

At least one type of surge supppressor relies upon the ground path to rid itself of excess voltage. That this may not be the 'latest' type is immaterial; for the purposes of this discussion, it's enough to know it exists.

It's getting pretty hard to find things around the home that don't use electronics .... I'm pretty sure my toilet doesn't - but I do have an old one!

Re: Replacement receptacles [Re: renosteinke] #184315 02/06/09 11:21 PM
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Posts: 65
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BrianP Offline
Member
I can understand that devices that function as switches (photocells, timers, etc.) may use the ground as a current path, since there is often no neutral in the box.

Yes, surge supressors will clamp surges between line or neutral and ground, and require a ground for that to work. The line to neutral protection should still work, but that is only 1/3 of the total function. Some of the more elaborate surge suppressors may use the ground for the line-neutral protection.

The original post was referring to a computer with an ungrounded outlet. Therefore, I was thinking mainly of electronics that plug in, not hard-wired devices.

In any case, having an actual ground is preferred even if the device still functions without it.

Sorry for any misunderstandings.

(I think you can find toilets with electronics in Japan, among other places!)


Re: Replacement receptacles [Re: BrianP] #184320 02/07/09 12:34 AM
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Posts: 1,507
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George Little Offline
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Brian- The "Ground" is not a normal current path for the items you mentioned. When a switch for example is turned on, the two wires (single pole switch) conduct the only current in the switch circuit. If one of these two wires shorts out to a grounded surface such as a metal conduit, then you are are correct the conduit now is a current carrying conductor. Quite often a switch, photo cell or mechanical timer are not fed with a neutral. If a switch has a pilot light on it or a timer has a motor then we would run a neutral to it.

I don't mean to talk below your level of training but I was confused by your statement about the switch, timer etc. If I miss understood your post I apologize.

Last edited by George Little; 02/07/09 12:35 AM.

George Little
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