I'm a little confused on using a 3 prong dryer outlet. If you set it up like P-J shows here, can this also be used to run 120V equipment like a pump? The third prong is ground, so you do not have a separate neutral. I've read this setup is only good for 240V elements. To run your pumps, you will have to run a 120V supply line as well.
Can this three prong setup be used for 120V as well as 240V in a panel?
The building wiring terminates with a 3 prong outlet that is 240V with a neutral. This wiring is according to code in place at the time that the wiring was done and is not being altered or modified in any way. If you alter it in any way, it must be brought up to current code. Dryers (and ranges) have both 240V & 120V devices that must be accomodated. Grounding (at that time) was accomplished by a jumper that goes between the neutral inside the dryer and the cabinet frame. The wiring setup I illustrate is a method of accomplishing the same thing and also provides GFCI protection. Keep in mind that the Spa Panel must be set up as a plug in device. If it is hard wired, the building wiring must be brought to current code.Sure, you CAN*, in the sense that it will work. Just take either of the 120V legs & neutral. You should probably run a separate ground wire.
*Notice this does not say you MAY do it. It may violate one or more local electrical codes, one or more sections of the NEC, etc. This is just a disclaimer; my attitude is- meh.
I hope this makes sense.