For Better Or Worse?

neolitic

To start with, I'm not trying to be a smart a$$ here, I'm trying to understand this,okay? That said I'm ready for Sparks to jump down my throat anyway, so here goes. I stuck one of those little Sperry 3 lite testers into a 3 prong outlet that I had grounded to the box after checking to see that the flex conduit ran all the way to the panel. It shows ground okay. Now I was told here earlier, that this wasn't a ground.
A) Isn't this a better path to ground than say through a person?
B) Should it still be taken out and replaced with a 2 holer?
Running an actual ground wire in this case (as with many others) just isn't gonna happen until there is MAJOR gut job on all three floors. Just want to know what's really better in the real world?
Some times even old guys still want to learn some things.

gravtyklz

It's a shame people have to ask questions and then 'duck and cover'...

neolitic

It's all good, I'm a big boy

Northernboy

Your Sperry 3-prong tester told you there was a good ground, but I don't know how much resistance to ground is needed to cause that tester to not light up. Flex (Greenfield) is not considered to be a good ground in lengths over 6 feet because it's one continuous metal strap spiraled around itself. Over time the worry is that the metal gets corroded or rusty and loses it's contact between the spirals creating a longer, higher resistance to ground. If the resistance is large enough the breaker won't trip on a short to ground through the flex. Replacing a 2 prong with a GFCI receptacle is a code compliant solution. As for "real world" I won't comment as I've seen too many people get their shorts in a bunch comparing real world to code world. I think most of us know how to make that grounding receptacle work, with a 2 inch jumper and be "electrically similar" to a code installation without using the flex as a ground.

Speedy Petey

It depends on the question and how it was asked.

__________________

neolitic

This time the question (seriously and respectfully) is, should I leave it or pull it? Comes up all of the time in old houses--I've got nothing I can plug my cords into, so...
From now on I'll take it out, unless they want to spring for a GFCI. But I really don't know if there is something more dangerous about what I've done than an ungrounded outlet.

Speedy Petey

neolitic, sorry. I meant nothing against you. I just think gravtyklz is still feeling the sting from a previous thread where the question asked was extremely basic for a supposed "pro".


First off, describe the "flex conduit". Is this greenfield flex, or are you simply referring to the AC cable itself?
If this is AC/BX cable, is there the thin bond strip run with the conductors? If so then the sheathing is a legal and safe ground.

__________________

neolitic

It' what I've always heard called Greenfield. It's 1920's vintage don't think they used the bonding strip then, and it's been too long since I had any of this exposed to say much more about it. I have seen newer stuff with that strip.

gravtyklz

Definitely still a little sore from that...but not really sure where the "pro" is coming from.

jproffer

I'm not speaking for Speedy, but I'm pretty sure it came from a combination of this:

and this: (I paraphrase)

All due respect, but this alone would be enough to demote you from PRO to "supposed pro", I would think.

__________________
Jim P.

gravtyklz

Yes thats under my trade not under my "knows everything about". But in anycase I dont wanna hijack someones thread over another one of these...

Sparky Joe

I'm no engineer, but it seems to me that the construction of flex is why it's not used as a ground as opposed to conduit.
This has nothing to do with corrosion over time because everything steel corrodes, and most flex nowadays is aluminum, but the rule still applies.

I'd say it's because the ground fault current carrying path is being run parallel to itself. One ring is parallel to the next, thus one ring's magnetic field would choke off the current carrying capability of the next ring. But each ring is touching, hence no more than 6 feet.

I know to most this may sound like I'm nuts, but I don't speak for the masses, rather to people who have a concept of electro-magnetism.

Northernboy

Serving 2 apprenticeships and more code update classes than I can remember, I was always taught the "poor connection between the spirals" theory for the 6 foot rule. But you make a good point Sparky Joe. I will have to sit and contemplate on "ELI the ICEman" for a while today.

It's better to burn out, than fade away -- Def Leppard

Northernboy

Why don't you just carry one extention cord with the ground snipped off, instead of replacing receptacles everywhere you go? Am I the only one who has one of those?

househelper

I really hope you are not serious about this?

But then I see you snip off plug grounds too....

Northernboy

Why not snip the ground if its a 2-wire rec. anyway. If you have an aversion to this then buy a plug adaptor and spend half the day trying to find it.

Northernboy

As for the seriousness of the jumper comment, I was trying to get a rise out of someone. It sure does fool those little plug-in circuit testers though!

Dustball

Wikipedia saves the day. Basically the conduit turns into an inductor- http://en.wikipedia.org/wiki/Inductor

http://electronics.howstuffworks.com/inductor1.htm

Northernboy

Don't look to hard Dustball, try "Lenz's law" or counter EMF

Dustball

I knew a bit about this from back when I was in school but as time goes by, the less I remember.