Originally Posted by bluedog_Brewing
I have the same 50A spa panel from HD and am considering wiring it to a 30A 3-wire (2xHOT + GRD) the way you recommend. However, my ground wire is bare (and maybe one size smaller than the 2 hot lines). Is it safe to carry current on a bare wire?
Actually that wire is the neutral conductor and, although it is a bare conductor within the cable, it is insulated by the outer cable sheath.
One must consider the power delivered to a dryer or to an electric range in the kitchen. The dryer and the range are not pure 240V units. Each of them have 120V devices within them (timer, controls, lights), so indeed the 3rd wire in the power cord is the neutral. Grounding in these devices is also provided by the neutral by using a bonding strap within it from the neutral to the cabinet frame. Current NEC code requires that a separate ground and neutral be provided. But that code applies to wiring that was placed after the code change. It does not apply to existing wiring.
Now, If you were just plugging into a 3 prong outlet for your brew rig, there would be no problem using that neutral as a common neutral/ground. However: Enter a GFCI into the plan and it's a new ball game.
The Spa Panel gives you the vehicle to provide GFCI protection. If your brewery power is from a 3 wire 240V outlet, the Spa Panel wiring I illustrated is your method to break out the ground and the neutral.
I hope this clarifies it for you and makes sense.