FAQ's- Myths and Misconceptions

[peter d]

I was wondering if the new FAQ section is going to contain answers to some of the more popular myths floating around in the electrical trade. I know myself and others have talked about this before so I hope I'm not beating a dead horse.


Some of the myths, with a detailed explanation as to why the are false, would be a nice feature.

Myths like:

</font>

• <font size="2" face="Verdana, Helvetica, sans-serif">Electricity is always trying to find a path to ground</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Multiwire circuits are unsafe.</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Grounding electrodes are there to "ground the system so the breaker trips"</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Working live is OK as long as you are qualified</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Receptacles should be installed with the ground up. </font>

<font size="2" face="Verdana, Helvetica, sans-serif">
Those are just a few that I can think of now, and there are many others.

 

[iwire]

Re: FAQ's- Myths and Misconceptions

Peter it sounds good to me.

 

[peter d]

Re: FAQ's- Myths and Misconceptions

Bob,

You may have trouble with that one, people have strong feelings on that just like grounds up or down.

Yup, you got that right.

My main goal is to evaluate everything from a safety standpoint. Mutiwire circuits are only unsafe to people who don't understand them properly. As has been said a million times before, we can't be designing and building electrical systems around the unqualified mind.

It will be very unfortunate if the NEC starts heading in that direction, and I for one don't want that to happen.

 

[electricman2]

Re: FAQ's- Myths and Misconceptions

Multiwire circuits are unsafe.

Until I joined this forum, I didn't know there was so much misinformation out there about multiwire circuits. I use them wherever possible. No sense running more wire than you have to.

 

[hurk27]

Re: FAQ's- Myths and Misconceptions

By Pete: we can't be designing and building electrical systems around the unqualified mind.

It will be very unfortunate if the NEC starts heading in that direction, and I for one don't want that to happen.

While I agree with this, But it's kind of exactly what the NEC does. But it goes one step further it also includes some codes for what could happen in end use by the user.
It just wouldn't have to be as big.

 

[frani]

Re: FAQ's- Myths and Misconceptions

I for one like to use multiwire branch circuits. But like you I listen to the unqualified complain that they are unsafe. The more they complain about them the more I realize how little they know about electricity. The ground up on outlets was the way I was trained as an apprentice. So....now it's just habit, as there's nothing in the code about it. They rational they had for installing them that way was logical.

 

[bill addiss]

Re: FAQ's- Myths and Misconceptions

Peter,

To answer your question, yes - the FAQ areas will be used. Those are good suggestions, we just have to come up with some good (and ironclad) wording.

Bill

 

[wirenut1980]

Re: FAQ's- Myths and Misconceptions

Not to bring up a touchy subject , but what is the misconception about multiwire branch circuits? And what is the truth about them?

 

[sandsnow]

Re: FAQ's- Myths and Misconceptions

Originally posted by hurk27:

If we have qualified electricans doing every job and we never had a problem would we need the NEC?
I would think yes.
It just wouldn't have to be as big.

 

[dema]

Re: FAQ's- Myths and Misconceptions

I got the Myth quiz, as I'm sure you all did. In school, I never saw the point to 'tricky' questions. It doesn't test what students know - just how savvy they are.

Electricity is trying to find the lowest resistance path from higher potential to lower potential. This frequently is the easiest path to ground.

Anyone want to argue with that?

In an ungrounded system, overcurrent protection frequently won't operate correctly. I realize that grounding stabilizes voltage and the circuit breakers trip on current, but having a 'safe', low resistance path for fault current does allow for predictable overcurrent protection.

The code states that the purpose of an effective ground fault path is to provide a low-impedance path for current in the case of a ground fault. If it isn't to make the touch potential safer, and it isn't to make overcurrent protection operate then what pray tell is it for? (Both answers were listed as false in these quizzes/myths).
Or is the answer to both questions 'false' solely because the code doesn't give the reason behind the reason? :roll:

The sum of the angles of a triangle is 180 degrees is also a false statement. Why? Because of Einstein's theory of relativity. It is only true in medium sized spaces - like the realm of everything that we can see, hear or touch on the face of this earth. When you get into outer space, the laws change, and it isn't true. You know what? If somebody asks me if the sum of the angles of a triangle equals 180 degrees - I'm going to say its true.

All right, set me straight if I'm misinterpreting.

 

[rbalex]

Re: FAQ's- Myths and Misconceptions

In the ?For What It?s Worth? department two ?unqualified? persons, the maker of Proposal 2-9 and the maker of the supporting Comment 2-4 to eliminate multiwire branch circuits, are on the NEC Technical Correlating Committee.

Philosophically, the ?unqualified? MUST be who we seek to protect first. The question that must then be asked is: ?When does that protection cease to be ?practical safeguarding??? Sometimes, ?Stay away from that, it could hurt you,? may be sufficient; usually it isn?t.

[ December 02, 2004, 12:48 PM: Message edited by: rbalex ]

 

[don_resqcapt19]

Re: FAQ's- Myths and Misconceptions

dema,
Can you point your comments to specific questions in Mike's quiz? Your comments are too general for me to make a reply.
Don

[ December 02, 2004, 04:10 PM: Message edited by: don_resqcapt19 ]

 

[jtester]

Re: FAQ's- Myths and Misconceptions

quote from deema
Electricity is trying to find the lowest resistance path from higher potential to lower potential. This frequently is the easiest path to ground.
Electricity follows ALL paths, not just the easiest or lowest resistance one. The current just divides unequally. Two people holding on to a 277 volt wire can get shocked simultaneously, not just the the one who represents least resistance path.

In an ungrounded system overcurrent protection frequently won't operate correctly.
I believe OCPD's will operate correctly, if applied correctly, they just don't operate for ground faults.

Jim T

 

[peter d]

Re: FAQ's- Myths and Misconceptions

Originally posted by bill addiss:
Peter,

To answer your question, yes - the FAQ areas will be used. Those are good suggestions, we just have to come up with some good (and ironclad) wording.

Sounds good Bill. I'm looking forward to it coming on line. Any idea of when?

 

[peter d]

Re: FAQ's- Myths and Misconceptions

While I agree with this, But it's kind of exactly what the NEC does.

Very true.

But when people propose rules for the NEC to start elimating efficient wiring practices, because they are viewed by some as "unsafe," well, that doesn't make a bit of sense to me.

Oh well, life goes on. Give me my multiwire circuits and I'm happy.

 

[iwire]

Re: FAQ's- Myths and Misconceptions

Originally posted by dema:
Electricity is trying to find the lowest resistance path from higher potential to lower potential. This frequently is the easiest path to ground.

Anyone want to argue with that?

Sure

No matter what spin you want to put on it electricity is not 'trying' to get to ground, it needs to go back to the source, the transformer, generator fuel cell what have you.

Many times the earth just happens to be a handy conductor back to the source,

Originally posted by dema:
In an ungrounded system, overcurrent protection frequently won't operate correctly.?

I would say that is false, the reason you use an ungrounded system is specifically so the overcurrent protection will not operate on the first ground fault.

As soon as a ground fault happens on ungrounded system a ground fault indicator should activate. At that point the ground fault is tracked down and repaired.

Even with the one ground fault everything runs OK and safely. If another phase ground faults during this time the OCP will operate immediately.

Remember that even with ungrounded systems all the metal parts are grounded.

Originally posted by dema:
I realize that grounding stabilizes voltage and the circuit breakers trip on current, but having a 'safe', low resistance path for fault current does allow for predictable overcurrent protection.

Are you still referring to ungrounded systems?

The operation of the OCP is entirely predictable on a correctly wired ungrounded system.

Originally posted by dema:
The code states that the purpose of an effective ground fault path is to provide a low-impedance path for current in the case of a ground fault. If it isn't to make the touch potential safer, and it isn't to make overcurrent protection operate then what pray tell is it for?

Lightning protection and high voltage imposed on the neutral from a utility company fault.

 

[bill addiss]

Re: FAQ's- Myths and Misconceptions

I'm looking forward to it coming on line. Any idea of when?

Peter,

The feature is online now. Danny (MHE Webmaster) did a great job setting it up. We just have to decide what to put in there and how it should be worded.

If anyone wants to make suggestions go right ahead. Remember, we need something that is absolutely correct, and wording that is easily understood.

Bill

 

[bthielen]

Re: FAQ's- Myths and Misconceptions

If we have qualified electricans doing every job and we never had a problem would we need the NEC?

Is it not that the definition of a qualified electrician is that he/she knows and follows the NEC and other applicable codes? Licensing and qualifying are not necessarily the same thing. I can be licensed but that doesn't mean I'll follow the codes. The need for inspectors is apparent here. I don't think anyone can truthfully disagree that without inspections, there would be a lot of "cutting corners" to save a buck. It's human nature. The fact that our work will be inspected helps keep us honest. Case in point, review the thread; "Who Uses NEC".

Bob

 

[bill addiss]

Re: FAQ's- Myths and Misconceptions

The fact that our work will be inspected helps keep us honest.

It also limits our liability.

Bill

 

[rbalex]

Re: FAQ's- Myths and Misconceptions

Originally posted by bill addiss:
...It also limits our liability.

Bill

How?

Every statute I've ever read, and it's probably in the 100's now, has something to this effect in it:

80.29 Liability for Damages . Article 80 shall not be construed to affect the responsibility or liability of any party owning, designing, operating, controlling, or installing any electric equipment for damages to persons or property caused by a defect therein, nor shall the _____ or any of its employees be held as assuming any such liability by reason of the inspection, reinspection, or other examination authorized.

I know this is now an 2005 "Annex" requiring specific adoption; but it is "model law." This concept is in every statute I know of that give AHJ's their "authority" in the first place. As far as I know, AHJ approval doesn't diminish anyone's liability in any jurisdiction I'm familiar with.

[ December 03, 2004, 01:36 PM: Message edited by: rbalex ]