Electrical Safety

To: Aquatic-Plants at actwin_com
Subject: Electrical Safety
From: svr at eecs_umich.edu (Steve Robertson)
Date: Wed, 13 Mar 1996 08:47:19 -0500
>
>From: User645273 at aol_com
>Date: Tue, 12 Mar 1996 16:15:27 -0500
>Subject: Re: Aquatic Plants Digest V1 #319
>
>In a message dated 96-03-11 03:53:35 EST, you write:
>
>>I had a look into another safety guide and it says 200mA. I had someone
>>here arguing with me that current won't kill but voltage do. Good luck
>>to him
>
>   I will agree with you 100%.  If it was voltage, then I'd be dead from the
>spark on my car.  The insulation on those spark plug wire doesn't always work
>quite the way its ment to :).  25000V hasn't killed me yet!
>
>Pete Datcuk
>

Allright.  I've been painfully listening to this discussion for the past
several days, and I can't take it anymore....

The *real* danger in working with electrical appliances in our aquariums
comes from the fact that the line voltage is _AC_ (alternating current).
This means that the 120 volt signal coming from our outlets is a sinusoidal
signal with a frequency of 60Hz.

Now, that said, AC current is far more dangerous than DC current for one
simple reason.

It takes only a small amount of AC current passing through your heart (here
is where the 200 mA number comes in) to defibrillate your heart muscles and
send you into cardiac arrest.  There may be little or no tissue damage
associated with this - 200 mA won't burn much of anything - but you could
be dead very shortly unless you have someone trained in CPR around at the
time.

200 mA of DC current, on the other hand, would do nothing more than make
you feel funny, if you felt it at all.

Now, like I said, the AC signal must pass through the heart to be truly
dangerous. Since your body is not a very good electrical path, it's usually
pretty hard to get that current to go through your heart muscles.  The
simple precautions that have already been mentioned (most importantly the
GFI circuit breaker) will provide adequate protection.  As an additional
measure, you should wear rubber soled shoes to prevent your body from
becoming a path to ground.

Sorry to drag this discussion any further.

Steve, in Ann Arbor where the sun came out yesterday...