On Sun, 19 Jun 2011 03:40:55 -0700, "William Sommerwerck"
wrote:

If I understand multi-phase wiring, the 240V is taken from across two
phases. Connecting or disconnecting the neutral would have no effect on that
voltage.

In single-phase systems, it would, of course, be foolish to switch just the
neutral. This would leave the hot "hot", and open the possibility of
electrocution from hot to ground, such as a plumbing fixture.


Yet again, an example of how a simple question becomes a tsimmes.

Residential wiring is, AIUI, typically "anti-phase" rather than multiple
(usually three) phase. One phase of the 3-phase distribution from the
substation is dropped with a center-tapped service transformer. The
center is earthed (at one point) and that becomes the neutral for the
120 volt services. 240 volt service doesn't have a neutral; both sides
are "hot" with respect to earth ground, so in the situation described
you'd expect to see 120 V to ground on the heater element.

Presumably, what you're seeing meets UL requirements. Perhaps (just
speculating here) the intent is that the oven should have an on-off
switch that does isolate both sources, and a thermostatic switch that
cycles on only one?

Also: tsimmes; I learned a new word! ;-)

--
Rich Webb Norfolk, VA