Date   : Thu, 17 Sep 2009 22:46:01 +0100
From   : pete@... (Pete Turnbull)
Subject: Leccy @ Acorn World '09

On 17/09/2009 11:04, Phil Blundell wrote:

> It's not such a bad system: the highest potential to ground at any point
> is 120V, and in most of the inhabited parts of a building the highest
> potential between any two accessible points would be 120V as well.  (The
> NEMA-14 outlets tend to be fitted in utility rooms and those kinds of
> places.)  So, compared to the European 230V system I guess they enjoy a
> slightly reduced shock risk.

Logical, on the face of it, but apparently debatable.  There's research 
to suggest that 120V is about the worst possible voltage. 
Unsurprisingly, lower voltages, below about 90V, induce such low current 
via skin resistance as to be unlikely to cause death, and yet, 
counter-intuitively perhaps, higher voltages are believed more likely to 
make you jerk away from the live conductor thereby breaking the contact. 
  That's why building site supplies in this country are 55-0-55V and 
never 0-110V.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York