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Electrical shocks


#1

I posted this a while back. It points out the potential dangers that
very seriously apply to electrical shocks. These can become a lethal
thing with the normal 115 volt supply voltage in North America— In
the parts of the world with 240 volt household supply the risks are
much greater.

Ground fault interrupters (GFI) have been required in the US and I
believe Canada about 25 plus years. They are required in bathrooms,
wet areas of kitchens and on exterior circuits as a minimum. I am
out of date on the codes but they will not have been reduced.
Issolation transformers are required for electrical equipment in
hospital environments. The Canadian codes are equal or possibly
superior to the US codes. I know nothing about requirements in other
parts of the world.

jesse

  1. Voltage doesn’t kill, current does.
  2. You are just a large resistor.

The following is taken from :

http://www.physics.udel.edu/~watson/scen103/colloq2000/safety.html

Note that the current has to pass thru the chest. You should visit
the link.

Current effects on human body, current through chest (A, amps)

<0.01 tingling or imperceptible
0.02 painful, cannot let go
0.03 breathing disturbed
0.07 breathing very difficult
0.10 death due to fibrillation

0.20 no fibrillation, but severe burning, no breathing

Mariss ran these tests on himself:

I set my multimeter to “mA”, connected it to a 60VDC supply, then
washed my hands but didn’t dry them. I grabbed my multimeter probes
in each hand and measured 1.2mA of current.

I then sprinkled table salt on my still wet hands and tried again.
The best I could get was 9.8mA and a barely perceptable tingling.

The internal resistance of a human body is about 500 Ohms. If your
skin were removed, it would then take about 50 volts to be lethal.

High voltages (115VAC, 230VAC) can kill by burning thru the skin at
the point of contact and then connecting to the much lower internal
body resistance. This takes time though, about 15 to 30 seconds at
230VAC. The heat generated is about 20W at the point of contact
(200V times 100mA) and takes that long to burn thru the skin.

The 9.8mA at 60V I tried generated a bit more than 1/2W (588mW) and
could do that; the body is simply too much of a heat-sink at that
power level.

As another reference said: “Electrocution is very difficult at
voltages below 100V, you must really work at it to succeed”.

Safety suggestions:

  1. Use only 1 hand when working with high voltages (115VAC or more).
    Keep the other hand behind your back; never rest it on anything.

  2. Don’t stand barefoot on a concrete floor or don’t stand on a wet
    concrete floor with shoes on when working with high voltages.

  3. When touching a high voltage, do it with the back of your hand or
    back of your finger first. Should there be a shock, muscle
    contraction will pull your hand away from instead of onto the
    conductor.

  4. Keep your hands dry. If they get sweaty, dry them often.

  5. Obviously, have the power off. Off means the plug is pulled from
    the wall. Always double check to see the pulled plug before you get
    into the equipment if you walked away from it for even a minute.
    Someone could have plugged it back in during your absence.

Mariss Freimanis


#2
  Ground fault interrupters (GFI) have been required in the US and
I believe Canada about 25 plus years. 

I think one can actually buy plug-in GFI units - plug unit into
outlet, then plug cord into unit. While perhaps not the ideal
solution it’s considerably cheaper than bringing in an electrician
and handing over your wallet.

Tas
www.earthlywealth.com


#3
I think one can actually buy plug-in GFI units - plug unit into
outlet, then plug cord into unit. While perhaps not the ideal
solution it's considerably cheaper than bringing in an electrician
and handing over your wallet. 

Yes, Tas, you can buy plug-in GFIs. I have the on all of the outlets
in my workshop.

Margaret