According to Wayne Whitney :
In article , HA HA Budys
Here wrote:

From: Wayne Whitney

1) My understanding is that for NEMA 6-15 (240V 2-pole Grounded 15
amp) plugs and receptacles, the two hot prongs are undistinguished,
i.e. there is no polarization as on 120V plugs and receptacles. Is
that correct? Is there any convention?

Correct. Both prongs are "hot" and there is no neutral. No polorization.

OK, just to be redundant, that means that in a 240V circuit, you don't
have to keep track of black versus red and you can connect black to red,
red to black willy-nilly?

Yeah, but it's _sloppy_.

On a related note, if I rewire a 120/240V induction motor to 240V and
change the 120V plug on its power cord, then I should mark the white
conductor at the new plug and at the motor junction box?

No, you do that on the 240V circuit if you're not using red and black conductor
wire. Not necessary on the power cord.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.