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Posted By: oktomorrow laptop used in bathtub dangerous? - 10/10/02 10:49 PM
Hi, I wanted to get the best, most authoriatative and expert advice I could find and believe I've come to the right place. I'm very concerned about my sister---she's in college and loves studying for hours every day in the bathtub---she's got a 5/8th's thick 1' x 3' plywood board running across the bathtub right in front of her---on that board sits her laptop computer, her mouse, not to mention books, papers, occasionally food or drinks, ETC. The laptop is not running on batteries---it's connected to the wall socket. If the mouse or laptop accidentally drops and is knocked off the board and into the water she is sitting in, is she a goner? She's been doing this for months now.
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/10/02 11:46 PM
hi oktomorrow.

ask if the receptacle that your sis is using is a GFI, if so have her test it with the buttons on it's face , they say 'test' and 'reset'.

theoretically, this limits the current to 4-6 ma should the lap top take the dive....

ps~ does she study marine biology? why the tub? [Linked Image]
Posted By: Bjarney Re: laptop used in bathtub dangerous? - 10/11/02 12:47 AM
Holey shi tzu.
Posted By: oktomorrow Re: laptop used in bathtub dangerous? - 10/11/02 01:15 AM
My sentiments exactly, Bjarney! Sparky, the outlet she is using is NOT equipped with GFI. The house was built a bit before that requirement was enacted. Even if the outlet had the GFI feature, I personally could not rest my life on it. They do malfuction and quit working occassionally I understand. Her love of the tub runs in the family, but she exemplifies the trait the most. ha. Thank you for your replies!

[This message has been edited by oktomorrow (edited 10-10-2002).]
Posted By: Redsy Re: laptop used in bathtub dangerous? - 10/11/02 11:08 AM
The laptop itself is fed through a transformer that lowers the voltage to the level required to operate the computer. However, if the transformer falls in with the computer, the line voltage (120 volt) will be applied to your sister while she is in the tub and she will die.
Posted By: txsparky Re: laptop used in bathtub dangerous? - 10/11/02 02:33 PM
Ask her to prearrange her funeral !!!
No doubt another Darwin award candidate!

[This message has been edited by txsparky (edited 10-11-2002).]
Posted By: oktomorrow Re: laptop used in bathtub dangerous? - 10/11/02 07:04 PM
The transformer would not fall into the water as it is across the bathroom about 7 feet away from the tub. It says input 100-240V and output says 16V - 3.75A---does that guarantee her safety if the laptop gets wets or falls into her bathwater? I wonder about the mouse too. Got an email from her today that said, "If it makes you feel any better I now have a reinforced tray with actual edges on it, that I am using. That way it lessens the chances of anything falling in." That didn't make me feel better even a little bit. The wall socket is not up to code, does not have GFI. My sister is an adult and I feel awkward even bugging her about this, but I see the danger as very real and have imagined her husband coming home and seeing her laying there dead. I figure now is the time to say something, not later. She reads what is written here, so please let her have it. ha. You just may save her life!



[This message has been edited by oktomorrow (edited 10-11-2002).]

[This message has been edited by oktomorrow (edited 10-11-2002).]
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/11/02 08:13 PM
uh..Sis...this is not good ok?
Posted By: pauluk Re: laptop used in bathtub dangerous? - 10/11/02 08:25 PM
I wouldn't be at all happy about this arrangement either.

Even if the transformer output is only 16V, it's amazing how much difference it makes when a body is totally immersed in water. It is on record that 32 volts has proved fatal, given certain circumstances.

Does this laptop have a modem and phone line connection as well? If so, let's not forget that a ringing phone line can have up to 120V AC superimposed on 50V DC. If that goes in the drink as well.... [Linked Image]
Posted By: electech Re: laptop used in bathtub dangerous? - 10/11/02 11:12 PM
The power transformer had to pass a leakage test (electricity, not water!) in order to get a safety listing. That's one hazard taken care of. I see very little real risk here - not that's it's a good idea to do what she's doing. Maybe a barely noticeable tingle from the 16 volts. I'm not vollunteering to put this to the test or anything... With a GFI I'd have no concerns whatsoever, aside from ruining a laptop.
Posted By: Bill Addiss Re: laptop used in bathtub dangerous? - 10/11/02 11:49 PM
I have a question for the more technical-type members here. Would the GFCI actually trip if the laptop fell in the water? I am wondering if a GFCI would really know what is going on the secondary side of the transformer.

Bill
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/13/02 08:25 PM
a worthy Q Bill,
it looks as if art 680 is peppered with GFI protection for 15V & up, 680.57 could concievably have a GFI do a ballast, and a secondary of higher voltage...
Posted By: Bill Addiss Re: laptop used in bathtub dangerous? - 10/13/02 08:47 PM
Sparky,

I'm wondering if a GFCI would see any imbalance on the primary side of the transformer at all. If I had to guess I would say no. I was hoping someone could say for sure.

Bill
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/13/02 10:11 PM
yes Bill, i too am curious, especially given examples of specific x-former design as specified in 680.23(A)(2) here,

Quote
(2) Transformers.
Transformers used for the supply of underwater luminaires (fixtures), together with the transformer enclosure, shall be listed for the purpose. The transformer shall be an isolated winding type with an ungrounded secondary that has a grounded metal barrier between the primary and secondary windings.

i believe, (although i can't seem to find it at the moment) that landsacpe lighting within a certian (10') distance of an outdoor hot tub also requires GFI protection of the branch circuit.

Having done this recently, i had the very same Q's.... [Linked Image]

The only angle i could possibly venture is of limited power (in oktomorrow's case 16x3.75= 60w)

heellllp!

calling all X-former pro's !!!
Posted By: Gwz Re: laptop used in bathtub dangerous? - 10/13/02 10:29 PM
Convince her to use the battery power while she is in the tub and with-out any type of cable (phone, CATV, printer, etc ) connected to that lap-top.

Living is much better than frying in water.
Posted By: pauluk Re: laptop used in bathtub dangerous? - 10/14/02 08:29 PM
Bill,
Quote
Would the GFCI actually trip if the laptop fell in the water? I am wondering if a GFCI would really know what is going on the secondary side of the transformer.

No it wouldn't. It would make no difference if the 16V secondary side were grounded or floating. Either way, it's not going to unbalance the primary current.
Posted By: Bill Addiss Re: laptop used in bathtub dangerous? - 10/15/02 01:32 AM
Thanks Paul,
That's what I thought. So, the GFCI in this case would offer no protection.

Bill
Posted By: Belgian Re: laptop used in bathtub dangerous? - 10/16/02 11:06 AM
>No it wouldn't. It would make no difference if the 16V secondary side were grounded or floating. Either way, it's not going to unbalance the primary current.

If the transformer is a electronic one and that your GFI is a type which can detect unbalanced DC as well as AC currents, then there is a possibility that it will trip.
Posted By: C-H Re: laptop used in bathtub dangerous? - 10/16/02 05:09 PM
Quote

If the transformer is a electronic one and that your GFI is a type which can detect unbalanced DC as well as AC currents, then there is a possibility that it will trip.

I can't see any way the GFI could see the difference between a normal load and a "human" load. Like Pauluk said, the current on the secondary side will just go from one pole to the other. But then, there is a lot I don't know about electronic transformers.

I've seen that many new RCD/GFI:s are advertised as DC-sensing (class A), but I thought this meant rectified DC at mains voltage. (When there is no transformer, just a rectifier)

I think you are perfectly safe in a bath with 16V DC. (Here you are allowed to have cables for 30V ripple-free DC in the bath tub.) I'd be a lot more worried about a transformer on a wet bathroom floor.

[This message has been edited by C-H (edited 10-16-2002).]
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/16/02 07:07 PM
I am at a loss for NEC rationale reading this, why would a particular x-former be specified if the GFI feed to it's primary side provided no protection to it's secondary?
Posted By: pauluk Re: laptop used in bathtub dangerous? - 10/18/02 02:58 PM
Yes, if it's an "electronic transformer" with an electrical path between input and output, then a ground fault could cause the GFI to trip, so long as it is a DC-sensing type. (Note that many will detect pulsing DC, such as you would get as the raw output from rectified AC, but they won't trip on pureDC).

Such power units aren't really transformers in the true sense of the word. With a real, genuine transformer with no direct electrical connection between the windings, a ground fault on the secondary will not trip a GFI on the primary.

Sparky,
You could even set up one of the SWER systems we were discussing some months back and have the secondary of the xfmr feed into the single wire. You could still put a GFI on the primary and it wouldn't trip, even though the full load current is flowing through the earth on the secondary side.
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/18/02 10:05 PM
I see.. there is no direct connection to produce the imbalance necessary for the GFI to function, thanks Paul [Linked Image]

What i don't understand is the rationale behind some NEC codes that would specify this to be so.... [Linked Image]
Posted By: jlhmaint Re: laptop used in bathtub dangerous? - 10/19/02 01:31 AM
well guys this sounds like and experiment in the works

who has a spare transformer plug, a gfi protected outlet and a bath tub. lets find out for sure.

girl use the batteries or get the #@!! out of the tube life is to short.
Posted By: AlphaOperator Re: laptop used in bathtub dangerous? - 10/24/02 12:37 AM
She could use batteries... but what I was thinking was that if the laptop fell in the drink, would that make the batteries possibly short-circuit? An exploding lithium-ion battery sounds rather unpleasant, espicially if you're already nekkeid with no clothing to protect you. Yikes.

Plus... I mean... laptops cost between a thousand and a few thousand dollars!!! I mean, one splash, one slip, and the system could be toast!

Ironically, within the next few years we might see specially-designed terminals or computers for just this use.

(Goes off to invent the water-proof toaster.)
Posted By: sparky Re: laptop used in bathtub dangerous? - 10/24/02 10:35 PM
AlphaOperator,
while your at it, i'd really appreciate a breed of self-cleaning chickens
[Linked Image]
Posted By: spyder Re: laptop used in bathtub dangerous? - 10/27/02 03:16 PM
Common sense would say its a bad idea to use any type of electric device while on is sumerged in bath water.

Tell her to smarten up so we do not end up readng about her in the "darwin awards".
Posted By: cubby964 Re: laptop used in bathtub dangerous? - 10/30/02 06:18 PM
[Linked Image]
The situation described struck me as similar to that encountered in an operating room with a patient being operated on. I know that this person is not compromised from a health standpoint, but, she is compromised from an insulation standpoint. Meaning, the resistance of her skin has been reduced to the point that its resistance approximates that of the underlying tissue. To the point: the NFPA, the people that write the National Electrical Code, also write a code for health care facilities, NFPA 99. In this Code, in an operating room with compromised situations (such as this) they call for alarms on the electrical system whenever the voltage exceeds 20 milivolts and 5.0 miliamps. This is not to say that these values would be lethal to this person, or to a patient, however, they do represent safe values found through empirical evidence. However you view this, I believe that values significantly higher than these could easily be attained in this situation, whether or not the primary of the transformer is GFCI protected (they don't always operate at the proper levels). It doesn't pay to tempt fate. [Linked Image]

Any body know of research into the effects of electric effects on thoroughly saturated skin. I have been hit with 120 and slightly wet hands (winter) with insulated boots, it is much more intense than with dry hands. Yes I am a sparky.
Posted By: Joe Tedesco Re: laptop used in bathtub dangerous? - 10/30/02 09:13 PM
Isolated Power Systems Equipment
UL 1047, and NEC 517.140 may be helpful information.
Posted By: mccutter Re: laptop used in bathtub dangerous? - 10/31/02 06:25 AM
Here is how we settle this...have a certified electrician install a "good" GFI outlet, plug the laptop into it and while standing on a dry floor away from the tub (noone in it) throw the laptop into the tub and see what happens. This is the only way to find out for sure...
Posted By: NJwirenut Re: laptop used in bathtub dangerous? - 11/03/02 07:25 PM
Another thing to think about would be the backlight on the laptop screen. While the majority of the laptop circuitry operates on low voltage, the backlight behind the LCD screen is actually a small cold-cathode fluorescent lamp, running on a high voltage (200V+) supplied by an inverter circuit inside the laptop.

While power limited, such a power source could be dangerous to someone in a bathtub if it got wet....
Posted By: Scott35 Re: laptop used in bathtub dangerous? - 11/16/02 08:15 AM
I was wondering how the Motherboard, Keyboard Contacts, Display and Disk Drives feel about the extremely high moisture level?!?!

Just another thing to consider and add to the list of "Don't Do Because Of:..."

Scott s.e.t.
Posted By: joeh20 Re: laptop used in bathtub dangerous? - 11/16/02 09:08 AM
I hope nothing happens to her, but it would be a different kind of Dell commercial, That kid Steven walks into the bathroom, startles the naked sister in the tub with Inspirion 4300 she knocks it into the water, and Steven says" Dudette you getting Electrocuted"
Posted By: OSHA Professor Re: laptop used in bathtub dangerous? - 12/16/02 12:39 AM
WOW ! Pretty esoteric analysis of power supplies, GFCI’s etc. etc. Did anyone suggest to check Charles Dalziels research work on electrocutions in human adults ?

May I respectfully suggest, that you suggest that she find something else to do in the tub …
If that dosen’t work help her maximize the computer time. Build her a platform for the car. Something that sits on the dash perhaps in front of the windshield then she can get more computer time in while driving.
Posted By: ThinkGood Re: laptop used in bathtub dangerous? - 12/19/02 10:34 AM
As if drivers with cellphones are not bad enough? ;-)
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