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115v cable danger: a myth ?

George Booth <booth at frii_com> wrote:

> I wouldn't worry too much about 115v cables. People use 115v heaters 
> (enclosed in glass!) all the time. 115v powerheads are very popular. When 
> is the last time you herd of someone killed by a broken heater or powerhead?

I have been searching the archives looking for info on heating cables. There
are several posts advising against the use of high-voltage cables (110 or 
220 V). The argument is always on the line of "water and electricity don't 
mix". I have a counter argument that I think can be posted here as food for 

I lived most of my 50 years in my native country, Brazil, where domestic
gas heaters to heat tap water are almost non-existent. I would bet that 
less than 1% of the households there have gas heaters. What people use to 
heat the shower water ? Electric shower heads ! They consist basicaly of a 
metal container (a few inches wide and high) that houses a HUGE bare copper 
coil. Water enters from one side, comes into direct contact with the bare 
wire and leaves from the other side at a pretty high temp. There is a 
spring-loaded rubber diaphragm that closes the electrical contacts when 
water fills the container and is under pressure, so it only turns on when 
water is actually running thru it. The thing makes a strong hissing noise. 
Of course, the metal container is grounded. I know these devices very well 
cause I used to take them apart to fix them. The power range is usually in 
the 1,500 to 2,500 Watt, but there are whole-house variants capable of 
feeding several hot water taps. These are usually in the  5,000 - 7,000 Watt 
range, with metal diaphragms, heavy-duty construction and are usually 
installed remotely, away from the hot taps. I had one of these in one of my 
houses once, in all other locations where I lived we had the regular 
showerhead type.

There migth be literally tens of millions of these devices all over the 
country. I researched the matter once and found that there was no single 
reported case of a death caused by electric showerheads. In decades of 
existence, and in millions of households. There have been some very rare 
accidents caused by human error, usually a device that was taken apart and 
them wrongly reassembled, or a poorly made ground connection. So my point is, 
given the proper, but very simple, safety features, water and electriciy CAN 
be mixed in a safe way. I wouldn't bother to have a 115 V cable in my 
aquarium, I had much scarier looking things hanging over my (wet) head for 
most of my life. An I am still alive.

Btw, most showerheads there are 220 V, mostly to save in wiring costs.

- Ivo Busko
  Baltimore, MD