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Question ??????

8K views 87 replies 27 participants last post by  BigJim 
#1 ·
here is a question ... FUN one ..

your standing in a bathtub full of water.... naked ... you put your right hand "IN" the neutral side of the GFI ...and your Left hand in the Hot side ( for the DIY ) would the GFI trip ...or would you get electrocuted ??


AND WHY !!!
 
#2 · (Edited)
I'm not an electrical engineer, but I believe the breaker would trip. The electricity sees far less resistance flowing through your body to the neutral side of the circuit than through your body and then the water, however that should simply mean that less current should flow through the water - but not zero. This of course assumes your plumbing is metal and goes to ground.

Interestingly, if you take the water out of the equation, you get electrocuted (because the GFCI sees you as a normal electrical appliance.) So in this case standing in water is safer than not! An apparent paradox, but that is how GFCI is meant to work.

Good question.

(The above is my guess at a hypothetical question, not the definitive answer, in case some idiot at home wants to try this.)
 
#10 ·
I'm not an electrical engineer, but I believe the breaker would trip.
What does being an EE have to do with it??? I'd bet most EE's don't even know the principle of how a GFI works.

And no, the breaker would NOT trip. :no: Not for a while at least.
 
#3 · (Edited)
Depends on how "good" a contact was made at each of the 3 points, fingers on receptacle slot contacts (2 places), and feet through water to metal drain fitting to plumbing system to gounding electrode conductor back to panel..

Some current will flow through your body between hot and neutral, and some current will flow through your body between hot and ground. If the latter is less than a few milliamperes, the ground fault interrupter unit will not trip and you could be electrocuted by the hot to neutral flow.
 
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#5 ·
The equivalent circuit for this is approximately three resistors in a wye arrangement. Two of them are your arms going to the receptacle slots, and the third is your body going into the bathtub. If the bathtub is grounded, then two points are at zero potential (right hand and feet) while the third is at 120V (left hand). So the result is that current flows in the left hand, and out both the right hand and the feet. The current out of the right hand would be similar to the current out of the feet (depends on the relative resistances of those body parts). This would trip the GFCI since a substantial amount of the current leaving the hot terminal does not return through the neutral, but instead goes to ground through the bathtub.

If the bathtub is fiberglass with a PVC drain line, the result may be different. The water in the tub is isolated from ground. Now the circuit is just hand-to-hand, and all current returns through the GFCI so it doesn't trip. You get electrocuted, but the bathtub has nothing to do with it.

One thing will definitely not happen: the breaker will not trip. There's no conceivable way that more than 15A will flow in this scenario. That would require a total resistance of 8 ohms or less, but body resistance is on the order of hundreds of ohms even neglecting skin resistance.
 
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#9 ·
Allan pretty much covered the points....

The kicker is that if your bathtub is a newer fiberglass tub with all ABS drains....chances are nothing will happen if you touch just the neutral or hot....the tub is effectively 'floating' (voltage wise), hence, no path to ground. In fact, you could be in the tub....drop a hot wire into the tub....and as long as you don't touch anything outside of it....your fine....

Now...when you touch both the hot and neut.....your a$$ is getting zapped....and I doubt the breaker will trip....should wake you up....
 
#15 ·
Electricity needs a path to flow.....

If the bathtub is fiberglass with all plastic plumbing....there is not electrical path to ground.

Ever see the guys who do the power line maint? Helicopter deposits them on the power line and the scoot down it without an issue....even though they are sitting at over 100K volts....no path between their body and ground.

As for tripping the breaker....while your body typically has a lower resistance than water....the amount of current flow is dependent on several factors...if the bathtub is 'floating' (not grounded)....you can touch either conductor but no current will flow. But, if you touch both of them...current will flow through your body.

It does not take much current for you to die....once again, several factors...your health...surface area of the contact between your fingers and the conductors, how much salt is in your body and on your skin...etc. But that current is really no where near the breaker trip point....so, grab both conductors with both hands and enjoy the ride....

Side note....grab both those wires with the same hand....it's going to hurt...could burn your fingers....but it's not going to kill you....not going through your heart....and it still won't trip the breaker...
 
#26 ·
you put your right hand "IN" the neutral side of the GFI ...and your Left hand in the Hot side
My question is why is that reversed ?

When you stand in front of a GFCI installed ground pin down, the neutral is on the left and hot is on the right. So, to follow the instructions you would be crossing one hand over the other. Based on the spacing most people would end up with a firm contact at the wrists.

Is that part of a trick question, or just mis-leading information ?
 
#34 ·
The thing about electrical engineers, or engineers in general is they usually only are good at what they specifically do. If their job doesn't utilize GFI protection, then they probably don't know much about it. I'll bet ya Speedy isn't too far off of his 90% statement.
 
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#35 ·
I'm the one who first mentioned electrical engineer, and the context was how electricity flows, not how GFCI operates. An EE who doesn't understand how electricity flows is like someone with a degree in English who can't read, or a degree in math who can't add. Let's get serious.
 
#36 ·
k_buz said:
The thing about electrical engineers, or engineers in general is they usually only are good at what they specifically do. If their job doesn't utilize GFI protection, then they probably don't know much about it. I'll bet ya Speedy isn't too far off of his 90% statement.
What a silly, overly broad and fact free generalization. Looks like someone has degree envy to me. Maybe income envy as well.
 
#40 ·
I’m new here, but Ill chime in because I’ve worked with EE engineers and electricians often. An Electrical Engineer is usually very specialized; he might design microchip circuits, signal processing systems, medical imaging equipment, computers, appliance, radio antennae, pretty much any electronic device, etc. etc. EE are responsible for the design of power distributiuon systems, generation stations/substations. EE design commercial/industrial building electrical systems. EE are hands off, they work on computers mostly.

Electricians are hands on. Electricians handle construction, repair of electrical power systems. Electricians are familiar with and know NEC very well. Electricians have less schooling than EE, but probably, for the most part make more $ than EE. Electricians die doing their job, EE do not. EE have taken math/physics courses that would make the very best electrician’s head explode.
 
#41 ·
Electricians are familiar with and know NEC very well.
It's funny you mention that, because half of the licensed electricians I talk to don't know the NEC. Half of them don't know how GFCI works (i.e. that it's leak detection.) Half of them think GFCI requires a ground wire to do its job. This is not a scientifically representative sample - it's anecdotal - but I'm not exaggerating.
 
#42 ·
There is a significant wealth of information and talented people on this forum....to go along with the attitudes and egos.

Not everyone can be an expert at everything like me....but some come close (like Dan H).

My FIL has a PHD in aerospace...but struggles to drive a nail in the wall. He can calculate the drag on a wing, but wouldn't know who to drag a box across the floor.

Everyone has specific talents...some are hands on trades...others are more in the design phase. Quite often a trade may not know how a GFIC actually works....and they guy who designed it may not know how to use the tools to install one.

We all just need to respect each others abilities and not take it personal when someone posts something contrary....lets try to debate it on technical terms and not make it personal.

Now....who is bringing the beer? It's Friday....taco/beer day.
 
#47 ·
There is a lot of talk about an EE not being able to do an electricians job. Have any of you electricians ever tried to do an EE's job? Ever tried designing a computer system board? What a joke that would be.

We all have different educational and job training backgrounds. Just because you have run into some "holier than thou" EE somewhere along the line doesn't mean that we are all dumb asses. I have in fact met a couple of master electricians with questionable IQs.

Sharing what we know helps everybody. Sharing attitudes helps nobody.
 
#49 ·
here is a question ... FUN one ..

your standing in a bathtub full of water.... naked ...
... [/B]
Why naked? This tells me you are preverted!

...you put your right hand "IN" the neutral side of the GFI ...and your Left hand in the Hot side ( for the DIY ) would the GFI trip ...or would you get electrocuted ??[/B]
Why don't you try that? If you don't post back we will know the answer!

LOLOLOLOL
 
#54 ·


And, of course, electricians are good at what they specifically do and also the things that they don't specifically do.

The spectrum of what most good electricians do is pretty wide.

One of my problems is that many "educated" folks look down on trades people as if they are somehow inferior, or less intelligent.
Schooling does NOT = intelligence.
 
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#56 ·
I'm sure you're an honest guy mpoulton but I don't believe there is any way in the world the above statement could be correct. The amount of information out there today precludes that.
OK. Here is your chance. Tell us why we should care what you say you believe. Tell us about your many years of work experience and the thousands of people upon whose experience your knowledge is based.

Nobody has more respect for tradesmen than I do, especially electricians.
I don't think that anybody works harder, knows more, or has to put up with more crap than professional electricians. They deserve every ounce of respect that we can give them.

Engineering is a much broader field than that of electrical power systems and installation of electrical systems. Most engineers specialize in one particular area much like an electrician might focus on a particular type of service or system.

In my more than 50 years of work experience, I have worked with thousands of people, many of them were/are electricians. The ones who were the most successful were those who respected the knowledge and experience of those around them. The ones who didn't usually had the most problems and least success.

A good, healthy, vigorous discussion/argument is just that . Healthy and good for all involved, but to disrespect or put down someone because of their job title is DUMB.

I wonder who designs those power systems that electricians install, or the test equipment and tools they use to install them. Maybe engineers?

I would not like to try to get along without our hard working electricians or our engineers.
 
#57 ·
David, I'm not sure that is such a good idea.

This place is full of keyboard commandos.....this is the internet.....for all we know, JoeCaption has never even picked up a hammer....for all we know, his idea of a stud is competition at the bar.

Not everyone can be an expert like me....design control systems....PLC programmer extraordinaire....write PC software....Autocad..... awesome mechanical fab abilities...great woodworking talents.....talk anyone into handcuff....able to book a DUI in record time.....Jack of all trades, master of many.....

Proof? Click on the links in my signature.....

Yes guys...I'm awesome...but I try to stay humble.....bragging is not in my nature....
 
#60 · (Edited)
Not everyone can be an expert like me....design control systems....PLC programmer extraordinaire....write PC software....Autocad..... awesome mechanical fab abilities...great woodworking talents.....talk anyone into handcuff....able to book a DUI in record time.....Jack of all trades, master of many.....
Impressive credentials!! I am a Marine Corps combat experienced veteran. I have written software in Cobal, Fortran, Basic, C, C++, and Java. I have done a lot of AutoCAD, I have designed and built computer system boards (motherboards), I have worked in law enforcement, I have built houses and put in the electrical and plumbing, I have done a little bit of Commercial wiring. A couple of years ago, I started learning to weld. TIG, Stick, MIG, and O/A. I rebuild automobile transmissions and engines. Oh yea, and I AM an engineer.

It sounds like we have a lot in common. Maybe we should get together and talk.
 
#62 ·
........and I'm old....I cut my teeth on a PDP-1134....
Well, I guess that's what experience does to us.....makes us old. I remember the PDP-1134 very well. I spent a couple of years using and maintaining a couple of those. My first home computer was actually a home built and modified Apple computer. Then the 8088 machines followed by the 8086, 80186, 80286.......etc. Actually the 8086 preceded the 8088, but the 16 bit support chips were expensive, so the 8088 was built so that 8 bit (cheaper) chips could be used.

I guess that I must come across as one of those "know it all" types, but actually, I don't feel that way at all. I very much appreciate the knowledge and experiences of others and enjoy sharing what took so many years of effort to learn. Maybe that is why I appreciate the professionals so much who willingly give so much of their time sharing their knowledge and experience on this forum.

Yes, I am old, but I still enjoy sharing and learning new things.
 
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