You forgot two major assumptions:
1) The impedance of the water and 2)the impedance of the human in water. In water, the human has orders of magnitude of lower impedance, and therefore, the majority of the current will flow through the human assuming there is a path to ground. It is highly unlikely that there is no path to ground. In most home building codes, plastic piping is not allowed due to fire codes (they melt) perhaps with the exception of waste pipe (most of them are cast iron) Recently in the bay area, a girl was electrocuted in a swimming pool due to a faulty lighting wire. Yes, the breaker triped but too late. Also, don't forget that there are many unsuspecting grounds. The faucet, dings and scrapes on the porcelain or enamel, wet wood, concrete, stucco, morter etc. Those are all better conductors than tap water. Hans ______________________________ Reply Separator _________________________________ Subject: GFIs, Hairdryers, and Bathtubs ... Author: Non-HP-dmckean ([email protected]) at HP-ColSprings,mimegw5 List-Post: [email protected] Date: 8/13/97 9:51 AM Recently somewhere back in the news (couple of weeks ago), two children died when one of them used a hairdryer in the tub. A discussion this accident with some lead me to a counter-intuitive result from my experience in product safety. ************************************************** Given Situation #1: 1. Person in a tub of water sitting at the opposite end of the tub than the drain. 2. The tub is ungrounded with water in it. Ungrounded meaning that the drain is plastic piping. 3. A 2-wire hair dryer (either On or OFF) is dropped into the water at the drain end of the tub. The person in the tub is neither in contact with the hairdryer, not anything that would be grounded. The hairdryer has a plastic case. Result: 1. Since there is no path to ground from the hairdryer through the person in the tub to ground, no current should flow *thru* the person in the tub. The person is in no harm. 2. Since no current is flowing through ground, the GFI won't trip. If the water allows sufficient current to flow by shorting between the HOT and NEUTRAL in the hairdryer, the breaker will trip. ************************************************** Given Situation #2: Same as situation #1 except that the drain is now a grounded metal pipe. Is there a sufficient parallel path to be lethal to the person in the tub? Seems as though the parallel path for the hairdryer is straight to the drain. Result: 1. Person is still unharmed. 2. GFI trips. ************************************************** Are my conclusions correct? Is the only time one can be electrocuted in a tub when they are in contact with a ground and holding the hairdryer? Is a person really killed in a tub with hairdryer by drowning rather than electrocution? I'm beginning to doubt that I know exactly how a person is killed in a tub with a hairdryer. Or, am I making this way more complicated than it is? Comments?
