Path: utzoo!attcan!uunet!ncrlnk!ncrwat!swdev!tp2!howard
From: howard@tp2.Waterloo.NCR.COM (Howard F. Steel)
Newsgroups: sci.electronics
Subject: Re: Polarized Plugs for 120 VAC
Keywords: house, wiring, safety, single phase, USA
Message-ID: <293@tp2.Waterloo.NCR.COM>
Date: 15 Nov 88 18:17:07 GMT
References: <686@bnlux0.bnl.gov> <4759@bsu-cs.UUCP>
Reply-To: howard@tp2.Waterloo.NCR.COM (Howard F. Steel)
Organization: NCR Canada Ltd., Waterloo, Ontario, Canada
Lines: 28

In article <4759@bsu-cs.UUCP> dhesi@bsu-cs.UUCP (Rahul Dhesi) writes:

>It seems to me that it would be far safer to have each of the two hot
>wires be at +/- 55 volts relative to ground.  A grounded center-tapped
>secondary would do it.
>
>Touching both would be just as lethal as before.  Touching one and
>ground at the same time would be much safer.

Safer, yes. Safe, No. It has been concluded that voltage levels below 30Vrms
(42.4V peak) are "Touch-Safe", otherwise designated as Safety Extra Low Voltage
(SELV). The level of 55Vrms in your scheme is still almost twice this limit.
In addition, to the above you must consider the energy hazard; 240VA and above
is considered to be such a hazard. Considering a normal 15A outlet, you have in
excess of 800VA, 3-4 times the limit; this represents a fire hazard if exposed.
In order to reduce this hazard, the service would have to be limited to less
5A, (run your heater on that if you will).

I have only seen one safe outlet/appliance combination, that considers even the
dolts among us who like sticking their tongues in outlets, and that was devised
by Manning Rose of NCR (Dayton). Rather than go into the details of it here,
suffice it to say that it all boils down to a matter of cost; the cost in
changing the present standard to a new, albeit better system. Maybe if Manning
is reading this he could shed some expert advice on the whole affair.

-- 
Howard.Steel@Waterloo.NCR.COM  :-(  	I Think, Therefore I AM,
aka: Howard "The Duck" Steel   :-) 		I think