31 Jan
2011
31 Jan
'11
12:26 p.m.
On Sunday, January 30, 2011, Brian Lanning wrote:
I thought there used to be an (IMHO dangerous) bit in the US elcectircal
regualtiosns which allowed cookers to have a 3 wire mains cable (the 2
phases and protective gorund., the last being wired ot the metal frame of
the cooker) but they coulsd still have a 110V timer wired from one phase
to the _protective ground_ wire.
Taht wouldn't work in Europe (since the 2 sides of the 230V mains are not
balanced about ground), and anyway AFAIK making the protecive ground wire
carry any current under normal conditions is totally forbidden.
In the US, two separate 110 legs are delivered to
the house. When we
need 220, the magic of constructive interference is applied, and we
get 220. The 220 is delivered to the appliance as two separate 110
wires, a neutral wire, and sometimes a separate ground wire for
safety.
Some things don't have a separate neutral line, in which case they don't
require 120V power. Because of this arrangement, sometimes appliances
(I believe, maybe
I'm wrong) will pull 110 from one of the legs to power electronics in
the appliance.
Yes, some do that. You can always wire in a 240V to 120V step-down
transformer to run the extra bits. It's rarely much power (timers,
clocks, etc), so you probably could get away with a 100W or so step-down
transformer, which should be pretty cheap.