wrote in message
news:1080629001.392160@smirk...
For complicated reasons (see below), I need to run two 120V 20A outlet
circuits as an Edison circuit (shared neutral), and they have to be
protected by GFCIs. I can't just use GFCI outlets.

Why not, you didn't say. Not enough room in the wiremold boxes? There are
square boxes with a rectangular cutout on the back, typically used to put a
box on top of drywall that has a box and a mud ring behind it. You could
bolt those tight to the front of the wiremolds; it'll look a bit ugly but
will give you the requisite space.

Don't use a 240v breaker. Electrically it would work but it ties the two
circuits' overcurrent protection together. NEC requires independent
overcurrent protection for each circuit.

The 20A circuits (except for things like hot tubs and pools) don't require
GFI (even though you could use it if you want) because the equipment that
uses it is generally very sturdily grounded. You can't plug portable
lamps, fans, and other such things with skimpy or no grounding protection
into those circuits. As far as electrocution hazards, the higher current
capacity doesn't mean squat; even a 1 amp circuit would be more than
sufficient to carry a current that would kill you.