Originally Posted by kevin509
If going from 3-wire 240V into spa panel as shown would I still get to use 120V off one of the 240V legs like I am now with 4-wire 240V? If so that would be awesome as I built my panel around 4-wire 240V then moved to older apartment where both dryer and range are 3-wire and I'm stuck with running extension cords for pump and power for BCS-460 controller.
It will work. You will be using an equipment ground as a neutral though. This was allowed in the past as a way around supplying a neutral to 120V control systems in 240V appliances. A bare ground wire is not intended to carry current. If you are using it that way it is "technically" not correct.