Another sad reminder of why we require GFCI's

[charlie b]

OK, we are either agreeing by saying ?I don?t agree,? or we are disagreeing by saying ?You are right.? Let?s try this again.

If the tub truly is isolated, no metal nearby at all, then any current that flows through the water (and the bather) will start at the hot leg, and return via the neutral. This will not trip the GFCI.

If the tub is not completely isolated, if the pipe is metal for example, then the current that passes through the bather?s body can return to the source via the metal pipe. This should trip the GFCI.

One more thing: Even if the tub is ?isolated,? as described above, and even if all the home?s pipes are plastic, and there is no GEC connection to a water pipe, then while the tub is draining there is another possible path for the current to take. If the serving utility uses metal pipes, even 10 feet or more from the home, current can flow through the water, into the utility?s metal water pipe, then through the dirt to the home?s ground rod. I strongly suspect that if a hair dryer is accidentally dropped into the tub, the bather will remove it before starting to drain the tub. But if the tub has started draining, and if the person knocks the hair dryer into the tub while trying to step out of the tub, there might be a shock, and a GFCI device would stop that shock from becoming fatal.

 

[pfalcon]

If the tub is not completely isolated, if the pipe is metal for example, then the current that passes through the bather?s body can return to the source via the metal pipe. This should trip the GFCI.

Emphasis on should. If the electrical leak is <5ma then it won't trip. It also may not kill. Larger leaks (>4ma) will cause a trip that is time restricted based on the leak size.

GFCI "minimizes" the risk of electricution but does not eliminate it. The larger the leakage current then the shorter the exposure period.

 

[LarryFine]

We have no idea if the piping to the tub was metallic or non-metallic. If it is non-metallic it may have enough isolation so that the GFCI does not trip.

In that case, the electrocuting voltage would have had to originate and terminate within the appliance case. Even a hand holding the handle, where the switches often are located, should not take current through the body.

Current through a conductive medium would form a three-dimensional elliptical pattern (like a football) around the voltage points, similarly to lines of flux between magnetic poles, or potential shells about an energized grounding electrode.

Of course, anything is possible, but in my opinion, there should not have been a lethal current outside the dryer case unless the water/tub/piping (drain as well as supply) provided a substantial portion of the conductive pathway.

I could be way off base here, and if I am, I hope someone can show us any evidence of such. The article does not mention whether there was any form of GFCI protection in use, which would be an important part of our forensics discussion.

 

[LarryFine]

If the tub truly is isolated, no metal nearby at all, then any current that flows through the water (and the bather) will start at the hot leg, and return via the neutral. This will not trip the GFCI.

If the tub is not completely isolated, if the pipe is metal for example, then the current that passes through the bather?s body can return to the source via the metal pipe. This should trip the GFCI.

I agree 100% with both statements.

One more thing: Even if the tub is ?isolated,? as described above, and even if all the home?s pipes are plastic, and there is no GEC connection to a water pipe, then while the tub is draining there is another possible path for the current to take. If the serving utility uses metal pipes, even 10 feet or more from the home, current can flow through the water, into the utility?s metal water pipe, then through the dirt to the home?s ground rod. I strongly suspect that if a hair dryer is accidentally dropped into the tub, the bather will remove it before starting to drain the tub. But if the tub has started draining, and if the person knocks the hair dryer into the tub while trying to step out of the tub, there might be a shock, and a GFCI device would stop that shock from becoming fatal.

That's a stretch, but it's possible; and yes, the GFCI should respond.

 

[masterelect1]

Theoretical Hypothesis

Theoretical Hypothesis

I'm probably wrong here but here goes:

person in tub absorbs x# of ma upon device falling into tub, she goes through a period of electrical shock; her organs begin to absorb current and there is a time delay for the process of organ damage to occur (and forgive me for this analysis); would it not be similar to an inductive load where her organs were absorbing enough current to cause damage, and in the interim the gfci sees an imbalance and trips.

PS-It's only us here and not the family- just hoping to understand some things re: GFCI response. I defer to the EE's on this site as you all are much better educated than I.

Thanks,
John

 

[charlie b]

You have one misconception here. Nothing "absorbs" current. Current passes through things. It starts at a source, it goes along wires and sometimes along other things (like hands and internal organs), and it returns to the source. It does not build up inside a device (or a person).

If you draw a sketch of the electrical connections of any circuit, and draw a circle around any part of that sketch, the total current entering that circle along all paths (i.e., that cross the circumference of the circle) will, at every moment in time, be exactly the same as the total current leaving the circle along all available paths.

 

[don_resqcapt19]

Larry,

Current through a conductive medium would form a three-dimensional elliptical pattern (like a football) around the voltage points, similarly to lines of flux between magnetic poles, or potential shells about an energized grounding electrode.

Yes and the person in the water is part of that current path. The persons wet body will likely have a lower resistance than the water itself and the wet body will conduct current...maybe enough to be lethal.
Don

 

[pfalcon]

I'm probably wrong here but here goes:

person in tub absorbs x# of ma upon device falling into tub, she goes through a period of electrical shock; her organs begin to absorb current and there is a time delay for the process of organ damage to occur (and forgive me for this analysis); would it not be similar to an inductive load where her organs were absorbing enough current to cause damage, and in the interim the gfci sees an imbalance and trips.

PS-It's only us here and not the family- just hoping to understand some things re: GFCI response. I defer to the EE's on this site as you all are much better educated than I.

Thanks,
John

person in tub absorbs joules of energy and organs cook according to i squared r. GFCI protects against this damage since return is split between ground and neutral. GFCI should eliminate this hazard.

person in tub also gets hit with 60hz electrical energy. A good frequency to cause fibrillation where the heart beats out of sync and therefore fails to effectively pump blood. GFCI significantly reduces exposure time but does not eliminate it.

 

[smithacetech]

[/FONT]
One more thing: Even if the tub is “isolated,” as described above, and even if all the home’s pipes are plastic, and there is no GEC connection to a water pipe, then while the tub is draining there is another possible path for the current to take. If the serving utility uses metal pipes, even 10 feet or more from the home, current can flow through the water, into the utility’s metal water pipe, then through the dirt to the home’s ground rod. I strongly suspect that if a hair dryer is accidentally dropped into the tub, the bather will remove it before starting to drain the tub. But if the tub has started draining, and if the person knocks the hair dryer into the tub while trying to step out of the tub, there might be a shock, and a GFCI device would stop that shock from becoming fatal.

I would think that filling a tub would cause a more likely path to ground. Following the path you described above. The drain I believe is more than likely a PVC pipe all the way to the sewer. I could be wrong though.

It would be interesting to know the details of this terrible accident. I think all bath room related cords should be required to have a ground wire &/or an immersion detective device.

 

[stevemeade79]

Well, the girl was electricuted because her body (and the water) provided a path for electricity to go to ground, via the grounded water pipes. So in this case, if the hair dryer was plugged into a GFCI, it would have detected the leakage and triped the circuit, most likely before she recieved a fatal shock?

 

[ELA]

This type of potential electrocution has always made me curious. But not enough to do actual experiments.

Heres an attempt at estimating/calculating what current might flow in the case where the tub is isolated.
It includes values of resistivity of water both clean and not so clean -but not salty. It also accounts for higher water temperatures in the worst case.
Assumes a 1 foot distance from the body to the dryer.

I am not claiming it is totally accurate but helped me make a best guess at current levels that might flow. Who knows what contaminants might be in the water (not accounted for) and it would not take much for the conductivity of the water to increase to the level where more than 5 ma could flow.

The one thing I have never been able to find in my reseach is what current levels might be lethal when the entire body is submerged in the current path vs. a point of contact with wiring. These calculations seem to support a less likely possibility of death (assuming more than 5 ma required).

If a submerged body required less current (since the entire body is conducting) then electrocution might be more likely. Also as was already mentioned a person might not be able to get themselves out of the tub and might suffer a long exposure or drowning.

 

[Pierre C Belarge]

Yes the child may have been electrocuted, but... a 6 & 2 year old left alone in the tub. That is sad in itself, as those children should never have been left alone in a tub at that age.

 

[ceb]

Yes the child may have been electrocuted, but... a 6 & 2 year old left alone in the tub. That is sad in itself, as those children should never have been left alone in a tub at that age.

I fully agree with that statement, Pierre, and it has been interesting reading the post. However, what if there was no gfci. More than once, and I am sure I am not alone on this, have I been called to fix that "D" gfci it keeps tripping when I plug a drop cord in, only to find the cord looks like it has been ran over with a mower. This could have been the thought process IF some one replaced the gfci with a non-gfci or may have never had one installed in the first place

 

[electricmanscott]

The kicker here is that if GFCIs were being introduced right now half of you would be crying about the extra cost and the government intrusion.

(See AFCI'S and Tamper Resistant receptacles)

 

[electricmanscott]

a 6 & 2 year old left alone in the tub. That is sad in itself, as those children should never have been left alone in a tub at that age.

It's ridiculous that this is not as obvious to some people as it is to us.

 

[iwire]

It's ridiculous that this is not as obvious to some people as it is to us.

I think it's obvious to many of us.

But I have a hard time blaming a kid for being born to idiots.

 

[76nemo]

I think it's obvious to many of us.

But I have a hard time blaming a kid for being born to idiots.

That's pretty harsh Clint

 

[iwire]

That's pretty harsh

Your right, it was and it is not directed at any particular parents.

My point was no mater what, the kids are kids, and can not be expected to protect themselves and sometimes they are born to people that are not really ready to be parents.

 

[Pierre C Belarge]

My comment was not directed towards the children...it is unfortunate that the parent had other things to do than be a parent.

I know what it is like to have children.
It is constant 24/7 work. Don't get me wrong, there were plenty of days that if the one-way ticket to moon was available, my girls may just be up there.
GFCI or not the children need supervision at that age.